Thèses sur le sujet « Structure and evolution of the Galaxy »

La formation et l'évolution du disque épais de la Voie Lactée restent controversées. Nous avons utilisé un modèle de synthèse de la population de la Galaxie, le Modèle de la Galaxie de Besançon (Robin et al., 2003), qui peut être utilisé pour l'interprétation des données, étudier la structure galactique et tester différents scénarios de formation et évolution Galactique. Nous avons examiné ces questions en étudiant la forme et la distribution de métallicité du disque mince et du disque épais en utilisant l'approche de synthèse de la population. Nous avons imposé sur des simulations les erreurs d'observation et les biais afin de les rendre directement comparables aux observations. Nous avons corrigé les magnitudes et les couleurs des étoiles de la simulation, en utilisant un modèle d'extinction. Les modèles d'extinction disponibles ne reproduisent pas toujours la quantité exacte d'extinction le long de la ligne de visée. Un programme a été développé pour corriger la distribution de l'extinction en fonction de la distance le long de ces lignes. Les extinctions correctes ont ensuite été appliquées sur les simulations du modèle. Nous avons étudié la forme du disque mince en utilisant des données photométriques aux basses latitudes du sondage SDSS-SEGUE. Nous avons comparé qualitativement et quantitativement les observations et les simulations et nous avons essayé de contraindre la fonction de masse initiale. En utilisant la spectroscopie du relevé SEGUE, nous avons sélectionné les étoiles du turn-off de la séquence principale (MSTO) (Cheng et al 2012) et des géantes K pour étudier la distribution de métallicité du disque mince et du disque épais. Nous avons calculé une estimation de distance pour chaque étoile à partir de la relation entre les températures effectives et magnitudes absolues pour les catalogues observés et simulés. Ces deux catalogues ont les mêmes biais sur les distances, elles sont donc comparables. Nous avons développé un outil basé sur une méthode MCMC-ABC pour déterminer la distribution de la métallicité et étudier les corrélations entre les paramètres ajustés. Nous avons confirmé la présence d'un gradient de métallicité radiale de -0.079 ± 0.015 dex kpc−1 pour le disque mince. Nous avons obtenu une métallicité du disque épais au voisinage solaire de -0.47 ± 0.03 dex, compatible avec les résultats obtenus par les études précédentes. De plus, le disque épais ne montre pas de gradient, mais les données sont compatibles avec un gradient positif intérieur suivi d'un négatif extérieur. Nous avons ensuite appliqué les outils développés au relevé spectroscopique Gaia-ESO et calculé la distribution de métallicité des étoiles F/G/K dans le disque mince et épais en supposant une formation en deux époques du disque épais de la Voie Lactée. Nous avons obtenu une métallicité locale dans le disque épais de -0.23 ± 0.04 dex légèrement plus élevée que celle obtenue avec SEGUE mais en accord avec Adibekyan et al. (2013) et un gradient de métallicité radiale du disque épais en accord avec notre analyse précédente des données de SEGUE et la littérature. La métallicité locale est en accord avec la littérature au niveau de 3σ mais parce que les données GES sont préliminaires, une analyse plus approfondie avec plus de données et de meilleurs calibrations doit être faite. L'existence d'un gradient plat dans le disque épais peut être une conséquence d'une formation à partir d’un gaz turbulent et bien homogène, ou bien un fort mélange radial a brassé après coup les étoiles<br>The formation and evolution of the thick disc of the Milky Way remain controversial. We made use of a population synthesis model of the Galaxy, the Besançon Galaxy Model (Robin et al. 2003), which can be used for data interpretation, study the Galactic structure and test different scenarios of Galaxy formation and evolution. We examined these questions by studying the shape and the metallicity distribution of the thin and thick disc using the population synthesis approach. We imposed on simulations observational errors and biases to make them directly comparable to observations. We corrected magnitudes and colors of stars, from the simulation, using an extinction model. The available extinction models do not always reproduce the exact quantity of extinction along the line of sight. A code to correct the distribution of extinction in distance along these lines have been developed and the corrected extinctions have been applied on model simulations. We studied the shape of the thin disc using photometric data at low latitudes from the SDSS-SEGUE survey. We compared qualitatively and quantitatively observations and simulations and try to constrain the Initial Mass Function. Using the spectroscopic survey SEGUE we selected Main Sequence Turnoff (MSTO) stars (Cheng et al 2012) and K giants to study the metallicity distribution of the thin and thick discs. We computed a distance for each star from the relation between effective temperatures and absolute magnitudes for the observed and simulated catalogs. These two catalogues have the same biases in distances, therefore are comparable. We developed a tool based on a MCMC-ABC method to determine the metallicity distribution and study the correlations between the fitted parameters. We confirmed a radial metallicity gradient of -0.079 ± 0.015 dex kpc−1 for the thin disc. We obtained a solar neighborhood metallicity of the thick disc of -0.47 ± 0.03 dex similar to previous studies and the thick disc shows no gradient but the data are compatible with an inner positive gradient followed by a outer negative one. Furthermore, we have applied the developed tools to the Gaia-ESO spectroscopic survey and computed the metallicity distribution of F/G/K stars in the thin and thick disc assuming a two epoch formation for the thick disc of the Milky Way. We obtained a local metallicity in the thick disc of -0.23 ± 0.04 dex slightly higher than the one obtained with SEGUE but in agreement with Adibekyan et al. (2013) and a radial metallicity gradient for the thick disc in agreement with our previous analysis of SEGUE data and the literature. The local metallicity is in fair agreement with literature at the 3σ level but because the GES data is an internal release under testing further analysis with more data and better calibrations have to be done. The existence of a flat gradient in the thick disc can be a consequence of an early formation from a highly turbulent homogeneous well mixed gas, unless it has suffered heavy radial mixing later on

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R similar to 22,500), high signal-to-noise ratio (>100), infrared (1.51-1.70 mu m) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design-hardware, field placement, target selection, operations-and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.

Cette thèse porte sur l'étude des propriétés et l'évolution de regroupement de galaxies pour les galaxies de la gamme de 22. Je ai pu mesurer la distribution spatiale d'une population générale de galaxie à redshift z~3 pour la première fois avec une grande précision. Je ai quantifié le regroupement de galaxie en estimation et la modélisation de la fonction de corrélation projetée (espace réel) à deux points, pour une population générale de 3022 galaxies. Je ai prolongé les mesures de regroupement à la luminosité et des sous-échantillons de masse sélectionné stellaires. Mes résultats montrent que la force de regroupement de la population générale de la galaxie ne change pas de redshift z~3,5 à z~2,5, mais dans les deux redshift va plus lumineux et des galaxies plus massives sont plus regroupées que les moins lumineux (massives). En utilisant la distribution d'occupation de halo (HOD) formalisme je mesuré une masse moyenne de halo hôte au redshift z~3 significativement plus faible que les masses halo moyens observés à faible redshift. Je ai conclu que la population de formation d'étoiles observé des galaxies à z~3 aurait évolué dans le massif et lumineux la population de galaxies au z=0. Aussi, je interpréter les mesures de regroupement en termes de biais de galaxies à grande échelle linéaire. Je trouve que ce est nettement plus élevé que le biais des galaxies redshift intermédiaire et faible. Enfin, je ai calculé le ratio-stellaire Halo masse (SHMR) et l'efficacité intégrée de formation d'étoiles (ISFE) pour étudier l'efficacité de la formation des étoiles et l'assemblage masse stellaire<br>This thesis focuses on the study of the properties and evolution of galaxy clustering for galaxies in the redshift range 22. I was able to measure the spatial distribution of a general galaxy population at redshift z~3 for the first time with a high accuracy. I quantified the galaxy clustering by estimating and modelling the projected (real-space) two-point correlation function, for a general population of 3022 galaxies. I extended the clustering measurements to the luminosity and stellar mass-selected sub-samples. My results show that the clustering strength of the general galaxy population does not change significantly from redshift z~3.5 to z~2.5, but in both redshift ranges more luminous and more massive galaxies are more clustered than less luminous (massive) ones. Using the halo occupation distribution (HOD) formalism I measured an average host halo mass at redshift z~3 significantly lower than the observed average halo masses at low redshift. I concluded that the observed star-forming population of galaxies at z~3 might have evolved into the massive and bright (Mr&lt;-21.5) galaxy population at redshift z=0. Also, I interpret clustering measurements in terms of a linear large-scale galaxy bias. I find it to be significantly higher than the bias of intermediate and low redshift galaxies. Finally, I computed the stellar-to-halo mass ratio (SHMR) and the integrated star formation efficiency (ISFE) to study the efficiency of star formation and stellar mass assembly. I find that the integrated star formation efficiency is quite high at ~16% for the average galaxies at z~3

Les grands relevés de galaxies sont des fenêtres ouvertes sur notre Univers: ils nous offrent de précieuses informations sur son contenu et sur son évolution. D'une part les relevés profonds explorent la formation et l'évolution des galaxies. D'autre part, les relevés à grand champ cartographient la distribution de la matière dans le but de comprendre la nature de l'énergie noire et de la matière noire.Au cours de cette thèse, j'explore les capacités offertes par ces relevés afin de répondre aux questions suivantes:1. Quels sont les principaux moteurs de l'évolutions des galaxies ? 2. Quelles progrès dans notre connaissance de l'Univers seront apportés par les futurs relevés de galaxies ? Je commence par déterminer la relation entre la masse stellaire et la masse des halos de matière noire des galaxies en utilisant des mesures précises de la fonction de masse stellaire dans le champ COSMOS. Grâce à l'exhaustivité du relevé COSMOS entre z ~0.2 et z ~ 5, j'obtiens pour la première fois cette relation sur une aussi grande gamme de redshifts à partir d'un seul relevé.Je constate que la masse de halo caractéristique, définie comme maximisant le rapport entre la masse stellaire et la masse du halo, augmente entre z=0 et z=2.3 et reste stable jusqu'à z = 4.Cette augmentation de la masse de halo caractéristique met en lumière le rôle des flux de gaz froid comme moteurs de la formation des galaxies à grand redshift. Afin d'approfondir ce sujet, je combine des observations de la teneur en gaz moléculaire froid des galaxies jusqu'à z=4, avec la relation entre masse stellaire et masse du halo de matière noire. Je constate que l'évolution de la fraction de masse du gaz froid est en accord avec l'hypothèse selon laquelle les apports de gaz froid sont responsables de la plus grande efficacité de formation des galaxies à grand redshift dans les halos massifs.Ensuite, dans le but de maximiser les contraintes cosmologique qui seront apportées par les prochains grands relevés spectroscopiques, je montre qu'une nouvelle observable, les fluctuations angulaires de redshift (ARF), apportent des informations complémentaires par rapport au traditionnel ``angular galaxy clustering''. Grâce à leurs sensibilités particulières au champ de vélocité de la matière, je montre que les dégénérescences entre les paramètres cosmologiques et de biais des galaxies sont différentes lorsqu'elles se basent sur les ARF ou sur le ``angular galaxy clustering''. Dès lors, la combinaison des deux observables permet de lever des dégénérescences et d'améliorer les contraintes, d'un facteur au moins deux, sur la plupart des paramètres des modèles ^CDM et wCDM.Finalement, en tant que membre de la collaboration Euclid, j'ai exploré le potentiel cosmologique de ce futur relevé de galaxies. Ce relevé nous permettra de mesurer très précisément la distribution de la matière sur tout le ciel extra-galactique. Dans le but d'exploiter entièrement tout son potentiel, il est crucial de le combiner avec les futurs relevés du CMB.J'utilise le formalisme de Fisher afin de prédire l'intérêt d'une analyse combinée des sondes CMB avec les sondes Euclid. Je teste à la fois le modèle ^CDM standard et ses extensions, et montre que le CMB améliorera les contraintes d'un facteur au moins deux sur la plupart des paramètres cosmologiques, et notamment sur les modèles d'énergie noire alternatifs, qui font partie des intérêts majeurs pour Euclid<br>Large galaxy surveys are like open windows on our Universe: they provide precious insights on its components and on its evolution. On the one hand, pencil surveys go deep into the cosmos to explore the formation and evolution of galaxies. On the other hand, wide surveys are mapping the distribution of matter on large scales to understand the nature of dark energy and dark matter.During my thesis, I explore the capabilities of these large surveys to address the following questions:1. What are the main drivers of galaxy evolution? 2. What improvements on our knowledge of the Universe will be brought by upcoming wide galaxy surveys? Using precise galaxy stellar-mass function measurements in the COSMOS field, I first determine the stellar-to-halo mass relation through a parametric abundance matching technique. Thanks to the completeness of the COSMOS survey from z ~ 0.2 to z ~ 5, I obtain for the first time this relation over such a large redshift range from a single coherent sample.I find that the ratio of stellar-to-halo mass content peaks at a characteristic halo mass which increases up to z = 2.3 and remains flat up to z = 4.This steady increase of the characteristic halo mass questions the role of cold gas inflows as drivers of galaxy formation at high redshift.To address this question, I link observations of the cold molecular gas content in galaxies up to z = 4 to the evolution of the dark matter halo mass. I find that the joint evolution of cold gas mass fraction and halo mass is in agreement with the hypothesis of cold gas inflows being responsible of efficient galaxy formation at high redshift.With the scope of maximising the cosmological power of next generation spectroscopic surveys, I show that a novel cosmological observable, the angular redshift fluctuations (ARF) will provide complementary cosmological information in addition to the standard angular galaxy clustering. Due to its distinct sensitivity to the peculiar velocity field, I find that the cosmological and galaxy bias parameters express different degeneracies when inferred from ARF or from angular galaxy clustering.As such, combining both observables breaks these degeneracies and greatly decreases the marginalised uncertainties, by a factor of at least two on most parameters in the ^CDM and wCDM models.As part of the Euclid collaboration, I then investigate the cosmological power of the upcoming Euclid survey, which will offer us an exquisite measurement of the matter distributions on the full extra-galactic sky.In order to fully exploit all the potential of the Euclid survey it is crucial to combine it with upcoming CMB surveys.I use the Fisher formalism to forecast the benefits of performing a joint analysis of CMB probes with Euclid main probes (weak lensing and galaxy clustering). I test both the standard cosmological model, ^CDM, and its extensions, and show that CMB will improve the constraints by a factor two on most cosmological parameters, and most notably on dark energy modified models which are of key interest for Euclid

We present N-body and hydrodynamical simulations of the response of the Milky Way's baryonic disc to the presence of the Large Magellanic Cloud during a first infall scenario. For a fiducial Galactic model reproducing the gross properties of the Galaxy, we explore a set of six initial conditions for the Large Magellanic Cloud (LMC) of varying mass which all evolve to fit the measured constraints on its current position and velocity with respect to the Galactic Centre. We find that the LMC can produce strong disturbances - warping of the stellar and gaseous discs - in the Galaxy, without violating constraints from the phase-space distribution of stars in the Solar Neighbourhood. All models correctly reproduce the phases of the warp and its antisymmetrical shape about the disc's mid-plane. If the warp is due to the LMC alone, then the largest mass model is favoured (2.5 x 10(11) M-circle dot). Still, some quantitative discrepancies remain, including deficits in height of Delta Z = 0.7 kpc at R = 22 kpc and Delta Z = 0.7 kpc at R = 16 kpc. This suggests that even higher infall masses for the LMC's halo are allowed by the data. A comparison with the vertical perturbations induced by a heavy Sagittarius dSph model (10(11) M-circle dot) suggest that positive interference with the LMC warp is expected at R = 16 kpc. We conclude that the vertical structure of the Galactic disc beyond the Solar Neighbourhood may jointly be shaped by its most massive satellites. As such, the current structure of the Milky Way suggests we are seeing the process of disc heating by satellite interactions in action.

Bars are common in disc galaxies along with many associated structures such as disc-like bulges, boxy/peanut bulges, rings, etc. They are a sign of maturity of disc galaxies and can play an important role in their evolution. In this thesis, I investigate the specific role bars play in quenching the star formation in, and shaping of their host galaxies. In order to test how bars affect their host galaxies, I study the discs, bars and bulges of what is currently the largest sample of barred galaxies (~3,500), selected with visual morphologies from the Galaxy Zoo project. I perform multi-wavelength and multi-component photometric decomposition, with the novel GALFITM software. With the detailed structural analysis I obtain physical quantities such as the bar- and bulge-to-total luminosity ratios, effective radii, Sérsic indices and colours of the individual components. I find a clear difference in the colours of the components, the discs being bluer than the bars and bulges. An overwhelming fraction of bulge components have Sérsic indices consistent with being disc-like bulges. I compare the barred galaxies with a mass- and environment-matched volume-limited sample of unbarred galaxies, finding that the discs of unbarred galaxies are bluer compared to the discs of barred galaxies, while there is only a small difference in the colours of the bulges. I suggest that this is evidence for secular evolution via bars that leads to the build-up of disc-like bulges and to the quenching of star formation in the galaxy discs. I identify a subsample of unbarred galaxies that are better fitted with an additional component, identified as an inner lens/oval. I find that their structural properties are similar to barred galaxies, and speculate that lenses might be former bars. Using the decompositions, I identify a sample of 271 late-type galaxies with curious bars that are off-centre from the disc. I measure offsets up to 2.5 kpc between the photometric centres of the stellar disc and stellar bar, which are in good agreement with predictions from simulations of dwarf-dwarf tidal interactions. The median mass of these galaxies is 10^9.6 M_⊙, and they are similar to the Large Magellanic Cloud, which also has an offset bar. Very few high mass galaxies with significant bulges show offsets, thus I suggest that the self-gravity of a significant bulge prevents the disc and bar from getting displaced with respect to each other. I conduct a search for companions to test the hypothesis of tidal interactions, but find that a similar fraction of galaxies with offset bars have companions within 100 kpc as galaxies with centred bars. Since many of these galaxies appear isolated, interactions might not be the only way to produce an offset bar. One suggested alternative is that the dark matter haloes surrounding the galaxies are lopsided, which distorts the potential, and imprints the lopsidedness and offsets onto the galaxy discs. I investigate the asymmetries in the kinematics of a subsample of such galaxies using data from the MaNGA survey, and find that the perturbations in the haloes are ~ 6% for both galaxies with off-centre and centred bars. I also measure the amplitude of non-circular motions in the outer discs due to an oval potential and find only minor departures from circularity, suggesting that the dark matter haloes are consistent with being spherical (axis ratio q ≳ 0.96). Therefore, the lopsidedness of the dark matter haloes cannot be the origin of the offsets. Either small companions are missed due to the incompleteness of the Sloan Digital Sky Survey spectroscopic survey, or interactions with dark matter satellites might explain the offsets. Modeling the kinematics of these galaxies, I find that the Hα gas rotation is centred closer to the centre of the bar than the centre of stellar rotation, suggesting that, in general, the bars are located closer to the dynamical centres of these galaxies than the discs. This implies that the discs are offset in these galaxies, not the bars. If offsets are characteristic of low mass galaxies only, high mass galaxies show vertically extended bars, known as boxy/peanut bulges. I investigate, for the first time, the formation and evolution of these structures associated to bars, from z≈0 to z=1. I compare two samples of moderately inclined galaxies with masses M_* > 10¹⁰ M_⊙, imaged by the Sloan Digital Sky Survey and the Hubble Space Telescope. Using a novel technique to classify bar isophotes, and based on the visual inspection of three expert astronomers, I find an evolving fraction of galaxies having boxy/peanut bulges from 30% at z≈0 to ~ 0% at z=1, and a strong correlation with stellar mass. I find 26 galaxies (15 at higher redshifts) in the phase of bar buckling, the mechanism proposed to form boxy/peanut bulges. The peak redshift of buckling is z≈0.75, where the bar buckling fraction is 4 times higher than in the local Universe. My observations suggest that many, if not all, of the boxy/peanut bulges are formed via buckling, ~ 2 Gyr after bar formation, with the buckling phase lasting for approximately 0.8 Gyr. I discuss my findings in the context of the evolution of barred galaxies and propose ideas for future work - applying similar decomposition techniques to higher redshift, and better resolution datasets, using integral field spectroscopic data to study the stellar populations of barred galaxies in greater detail, as well as a novel project to identify large nuclear discs in galaxies.

Je présente dans cette thèse de nouvelles contraintes sur la formation et l’évolution des galaxies, en étudiant leur croissance en masse et leur évolution au sein de la toile cosmique depuis l’époque de leur formation jusqu’à maintenant. Pour cela, j’ai créé un catalogue photométrique sur le champ COSMOS. Ce catalogue permet de sonder avec précision l’Univers à haut redshift. J’analyse ce relevé observé à l’aide de relevés virtuels, produits à partir de simulations hydrodynamiques. Ces simulations implémentent nos connaissances sur la formation et l’évolution des galaxies.Dans un premier temps, je montre que l’évolution en redshift des propriétés des galaxies est relativement bien comprise en invoquant des processus qui dépendent essentiellement de la masse, tels que le feedback des étoiles et des AGN. Je souligne également comment nos méthodes observationnelles génèrent des biais dans les propriétés physiques des galaxies calculées à partir de la photométrie.Dans un deuxième temps, je montre comment la dynamique des flots de matière à grande échelle gouverne l’acquisition du moment angulaire des galaxies et halos de matière noire, ce qui implique que certaines propriétés des galaxies sont supposées dépendre de leur environnement anisotrope. J’ai extrait la structure filamentaire du catalogue photométrique que j’ai créé sur le champ COSMOS et j’ai mesuré cette dépendance. Je trouve des gradients de masse et de couleurs dans la direction du filament. Il apparaît que la masse et le moment angulaire des galaxies sont deux quantités interdépendantes et tous deux impactés par leur environnement anisotrope<br>I present in this thesis new constraints on galaxy formation and evolution while studying the galaxy mass growth and the co-evolution of the cosmic web and the embedded galaxies, from the epoch of cosmic dawn to today.To do so, I first created a new photometric catalog on the COSMOS field with precise photometric redshifts allowing to probe accurately the high-redshift Universe. I analyze this survey while relying heavily on comparisons with virtual galaxy surveys produced from state-of-the- art cosmological hydrodynamical simulations, which capture all our current knowledge of galaxy formation and evolution.From this comparative analysis, in the first part of my thesis I show that the redshift evolution of galaxy properties is reasonably well understood when invoking mass-dependent processes (AGN and stellar feed- back). I highlight also the effect of simplifying assumptions inherent to our observational methods, which bias the physical properties computed from galaxy photometry.Galaxies and haloes are embedded in the cosmic web, an intricate large-scale structure of walls, filaments and nodes. In the second part of my thesis, I show how galaxies and dark haloes gain their angular momentum from the large-scale flow, implying that some of their properties depend on their anisotropic filamentary environment. I then extract the filamentary structure from the observed photometric catalog and measure the dependence of galaxy properties to the anisotropic environment. I find mass and colour gradients towards the filaments. In turn it emerges that galaxy masses and angular momenta are two dependent quantities impacted by their anisotropic environment

This thesis investigates the dynamical evolution of systems orbiting within deeper potentials. Initially we use a simple satellite-halo interaction to study the dynamical processes that act on orbiting systems and we compare these results to analytical theory. Deep images of the Centaurus cluster reveal a spectacular arc of diffuse light that stretches for over 100 kpc and yet is just a few kpc wide. We use numerical simulations to show that this feature can be produced by the tidal debris of a spiral galaxy that has been disrupted by the potential of one of the central cD galaxies of the cluster. The evolution of sub-halos is then studied in a cosmological context using high resolution N-body simulations of galactic mass halos that form in a cold dark matter (CDM) simulation. CDM halos form via a complex series of mergers, accretion events and violent relaxation. Halos are non-spherical, have steep singular density profiles and contain many thousands of surviving dark matter substructure clumps. This will lead to several unique signatures for experiments that aim to detect dark matter either indirectly, through particle annihilation, or directly in a laboratory. For the first time it is possible to construct maps of the gamma-ray sky that result from the annihilation of dark matter particles within simulated dark matter halo distributions.

The understanding of the origin and evolution of the Milky Way is one of the primary goals of the Gaia mission (ESA, launch autumn 2013). In order to study and analyse fully the Gaia data it will be useful to have a Galaxy model able to test various hypothesis and scenarios of galaxy formation and evolution. Kinematic and star count data, together with the physical parameters of the stars - ages and metallicities-, will allow to characterize our galaxy's populations and, from that, the overall Galactic gravitational potential. One of the promising procedures to reach such goal is to optimize the present Population Synthesis models (Robin et al. (2003)) by fitting, through robust statistical techniques, the large and small scale structure and kinematics parameters that best will reproduce Gaia data. This PhD thesis was focused on the optimization of the structure parameters of the Milky Way Galactic disc. We improved the Besançon Galaxy Model and then by comparing the simulations to real data studied the process of Galaxy evolution. The Besançon Galaxy Model is a stellar population synthesis model, built over the last two decades in Besançon (Robin and Crézé(1986); Robin et al. (2003)). Until now the star production process in that model was based on the drawing from the so called Hess diagrams. Each Galaxy population had one such a diagram, which was calculated once given a particular Initial Mass Function (IMF), Star Formation Rate (SFR), evolutionary tracks and age-metallicity relation and since then remained fixed in the model. As that feature was not enabling to test any other scenario of Galaxy evolution, because none of the evolutionary parameters could be modified, it was one of the biggest weaknesses of the model. It has served us as a motivation to dedicate this PhD project to the construction of a new version of the model, which would be able to handle variations of the SFR, IMF, evolutionary tracks, atmosphere models among others. When the evolutionary parameters are changed one must repeat the process of accomplishing the dynamical self-consistency of the model as described in Bienayme et al. (1987). For that we have recalculated the Galactic gravitational potential for all new evolutionary scenarios, which have been tested. The second very important improvement of the model, which is delivered in this thesis, is the implementation of the stellar binarity. That is, the new version of Besançon Galaxy Model presented here is not any more a single star generator, but it considers binary systems maintaining constraints on the local mass density. This is an important change since binaries can account for about 50 % of the total stellar content of the Milky Way. Once the tool was developed we tested several possible combinations of IMF and SFR in the Solar Neighborhood and identified those which best reproduce the Local Luminosity Function and Tycho-2 data. We have accomplished an unprecedented task using the new version of the model, namely we have performed the whole sky comparisons for a magnitude limited sample in order to study the bright stars. The Tycho-2 catalogue turned out to be an ideal sample for that task due to its two important advantages, the homogeneity and completeness until VT ~ 11 mag. Different techniques and strategies were designed and applied when comparing the simulated and the real data. We have looked at small and specific Galactic directions and also performed general comparisons with a global sky coverage. In order to increase the efficiency of numerous simulations and comparisons, a processing pipeline based on C, Java and scripting programming languages has been developed and applied. It is a fully automated, portable and robust tool, allowing to split the work across several computational units.<br>La misión Gaia (ESA, 2013) revolucionará el conocimiento sobre el origen y la evolución de nuestra Galaxia. Una óptima explotación científica de sus datos requiere disponer de modelos que permitan contrastar hipótesis y escenarios sobre estos procesos de formación. En esta tesis hemos optimizado el modelo de síntesis de poblaciones estelares de Besançon, ampliamente utilizado por la comunidad internacional, centrándonos en la componente del disco delgado. Hemos diseñado, desarrollado, implementado y testeado una nueva estructura de generación de las estrellas que permite encontrar la mejor combinación de función inicial de masa (IMF) y ritmo de formación estelar (SFR) que ajusta a las observaciones. El código permite imponer la autoconsistencia dinámica, recalculando el potencial galáctico para cada nuevo escenario de evolución. También, por primera vez, se generan sistemas binarios bajo esta consistencia dinámica, marcada por la función de luminosidad observada en el entorno solar. Esta, junto con el catálogo Tycho, han sido los dos ingredientes observacionales clave para el ajuste entre modelo y observación. También, por primera vez, hemos conseguido un ajuste aceptable a los recuentos estelares de todo el cielo hasta V=11. Se han evaluado con rigor los efectos en los recuentos estelares derivados del uso de los modelos de atmosfera, de evolución estelar y de extinción interestelar así como de parámetros tan críticos como la masa dinámica del sistema galáctico. El ajuste de estos ingredientes usando el catálogo Tycho nos ha permitido confirmar, de una vez por todas, que la SFR en el disco galáctico no ha sido constante sino decreciente desde los inicios de la formación de esta estructura. En conclusión, esta tesis proporciona un nuevo código, optimizado y flexible en el uso de los ingredientes básicos, en el que se ha realizado una rigurosa evaluación y actualización de los ingredientes que lo componen.

Cette thèse a pour but de faire le lien entre l’évolution des galaxies, leur morphologie et les processus physiques internes, notamment la formation stellaire comme le résultat du milieu interstellaire turbulent et multiphase, en utilisant les simulations cosmologiques zoom-in, les simulations des galaxies isolées et en interaction, et le modèle analytique de la formation stellaire. Dans le chapitre 1, j’explique la motivation pour cette thèse et je passe brièvement en revue le contexte nécessaire lié à la formation des galaxies et la modélisation en utilisant les simulations numériques. Tout d’abord, j’explore l’évolution de la morphologie des galaxies du type de la Voie Lactée dans la série des simulations cosmologiques zoom-in à travers l’analyse des barres. J’analyse l’évolution de la fraction des barres avec le redshift, sa dépendance en fonction de la masse stellaire et l’histoire d’accrétion de galaxies individuelles. Je montre en particulier, que la fraction de barres décroit avec le redshift croissant, en accord avec les observations. Ce travail montre également que les résultats obtenus suggèrent que l’époque de la formation des barres correspond à la transition entre une phase précoce “violente” de la formation de galaxies spirales à z &gt; 1, pendant laquelle elles sont souvent perturbées par les fusions avec les galaxies de masse comparable ou par multiple fusions avec les galaxies de petite masse, mais aussi les instabilités violentes de disque, et une phase "séculaire" tardive à z &lt; 1, quand la morphologie finale est généralement stabilisée vers une structure dominée par le disque. Cette analyse est présentée dans le chapitre 2. Étant donné que ces simulations cosmologiques forment trop d'étoiles trop tôt par rapport aux populations de galaxies observées, je me concentre dans le chapitre 3 sur la formation stellaire dans un échantillon de simulation de galaxies en isolation, à bas redshift, et à résolution du parsec et sous-parsec. J'étudie l'origine physique de leurs relations de formation stellaire avec les cassures, et montre que le seuil de densité surfacique pour une formation stellaire efficace peut être lié à la densité caractéristique d'apparition de turbulence supersonique. Ce résultat s'applique aussi bien aux galaxies qui fusionnent, dans lesquelles l'augmentation de la turbulence compressive déclenchée par les marées compressives les conduit au régime de sursaut de formation d'étoiles. Un modèle analytique idéalisé de formation stellaire liant la densité surfacique de gaz au taux de formation stellaire comme une fonction de la présence de turbulence supersonique et la structure associée du milieu interstellaire est ensuite présenté dans le chapitre 4. Ce modèle prédit une cassure à basse densité de surface qui est suivie par un régime de loi de puissance à haute densité dans différents systèmes en accord avec les relations de formation stellaire des galaxies observées et simulées. La dernière partie de cette thèse est dédiée à la technique alternative de zoom-in cosmologique (Martig et al. 2009) et son implémentation dans le code à raffinement de maillage adaptatif RAMSES. Dans le chapitre 5, je présente les caractéristiques de base de cette technique aussi bien que certains de nos tout premiers résultats dans le contexte de l'accrétion cosmologique diffuse<br>This thesis aims at making the link between galaxy evolution, morphology and internal physical processes, namely star formation as the outcome of the turbulent multiphase interstellar medium, using the cosmological zoom-in simulations, simulations of isolated and merging galaxies, and the analytic model of star formation. In Chapter 1, I explain the motivation for this thesis and briefly review the necessary background related to galaxy formation and modeling with the use of numerical simulations. I first explore the evolution of the morphology of Milky-Way-mass galaxies in a suite of zoom-in cosmological simulations through the analysis of bars. I analyze the evolution of the fraction of bars with redshift, its dependence on the stellar mass and accretion history of individual galaxies. I show in particular, that the fraction of bars declines with increasing redshift, in agreement with the observations. This work also shows that the obtained results suggest that the bar formation epoch corresponds to the transition between an early "violent" phase of spiral galaxies formation at z &gt; 1, during which they are often disturbed by major mergers or multiple minor mergers as well as violent disk instabilities, and a late "secular" phase at z &lt; 1, when the final morphology is generally stabilized to a disk-dominated structure. This analysis is presented in Chapter 2. Because such cosmological simulations form too many stars too early compared to observed galaxy populations, I shift the focus in Chapter 3 to star formation in a sample of low-redshift galaxy simulations in isolation at parsec and sub-parsec resolution. I study the physical origin of their star formation relations and breaks and show that the surface density threshold for efficient star formation can be related to the typical density for the onset of supersonic turbulence. This result holds in merging galaxies as well, where increased compressive turbulence triggered by compressive tides during the interaction drives the merger to the regime of starbursts. An idealized analytic model for star formation relating the surface density of gas and star formation rate as a function of the presence of supersonic turbulence and the associated structure of the ISM is then presented in Chapter 4. This model predicts a break at low surface densities that is followed by a power-law regime at high densities in different systems in agreement with star formation relations of observed and simulated galaxies. The last part of this thesis is dedicated to the alternative cosmological zoom-in technique Martig et al. 2009 and its implementation in the Adaptive Mesh Refinement code RAMSES. In Chapter 5, I will present the basic features of this technique as well as some of our very first results in the context of smooth cosmological accretion

Galaxy structures in the local Universe are the result of an evolution spanning billions of years. The diversity in morphologies observed is due to mechanisms that could either be from external interactions or internal processes. The hierarchical merging of two massive galaxies has long been thought to give rise to pressure-supported spherical structures, including elliptical galaxies and classical bulges. On the other hand, isolated galaxies may evolve at a much slower pace with the accretion of gas forming flattened rotationally-supported discs. Secular evolution could also result in newly formed internal structures, such as bars or discy-bulges. The first step in understanding the complex pathways that formed these monolithic beasts, we need to robustly measure their structures. This thesis investigates how the structure of galaxies have evolved over the last seven Gyrs. In the first part I present a new Bayesian Markov Chain Monte Carlo (MCMC) two-dimensional (2D) photometric decompositions algorithm called PHI. The purpose of the algorithm is to decompose a galaxy's light profile into the various components that make-up the structure. By implementing a three level method, PHI is able to obtain a full understanding of the parameter space overcoming many of the major issues previous codes have struggled with. The second part of the thesis describes the generation of synthetic galaxy images which are used to test the robustness of PHIand to also highlight the cosmological and instrumental effects that may bias the outcomes. We also present is a performance test for the Bayesian application to bulge-disc decompositions of galaxies using images from the Sloan Digital Sky Survey (SDSS), also included is the parameter estimation and model comparison method using the Bayesian Information Criteria. In the third part of this thesis we show how the use of Hierarchical Bayesian Models (HBM) can be used to describe structural scaling relations in the local Universe. A constant piece-wise representation fully captures the underlying nature of the sample. This leads to the analysis of many structural scaling relations, one being the positive trend between the effective radius of the bulge and the Sérsic index. Lastly, a study investigating the structural evolution of galaxies within the COSMOS field in the redshift range 0.5 < z < 1.25 is presented. The flexible nature of the HBM allows for a detailed description of the build-up of galaxy structures in the local Universe.

In this thesis, I develop and combine strong lensing and dynamical probes of the mass of early-type galaxies (ETGs) in order to improve our understanding of their dark and luminous mass structure and evolution. Firstly, I demonstrate that the dark matter halo of our nearest brightest cluster galaxy (BCG), M87, is centrally cored relative to the predictions of dark-matter-only models, and suggest an interpretation of this result in terms of dynamical heating due to the infall of satellite galaxies. Conversely, I find that the haloes of a sample of 12 field ETGs are strongly cusped, consistent with adiabatic contraction models due to the initial infall of gas. I suggest an explanation for these differences in which the increased rate of merging and accretion experienced by ETGs in dense environments leads to increased amounts of halo heating and expansion, such that the signature of the halo's initial contraction is erased in BCGs but retained in more isolated systems. Secondly, I find evidence that the stellar-mass-to-light ratio declines with increasing radius in both field and cluster ETGs. With M87, I show that the strength of this gradient cannot be explained by trends in stellar metallicity or age if the stellar initial mass function (IMF) is spatially uniform, but that an IMF which becomes increasing bottom-heavy towards the galaxy centre can fully reproduce the inference on the stellar mass. Finally, I use the sizes, stellar masses and luminous structures of two samples of massive ETGs at redshift z ~ 0.6 to set constraints on the mechanisms of ETG growth. I find that ETGs in dense cluster environments already lie on the local size-mass relation at this redshift, contrary to their isolated counterparts, and suggest that this may be evidence for their accelerated growth at early times due to the higher incidence of merger events in clusters. I also show that massive compact ETGs at this redshift are composed of a compact, red, spheroidal core surrounded by a more extended, diffuse, bluer envelope, which may be a structural imprint of their ongoing inside-out growth. Overall, the studies presented in this thesis suggest a coherent scenario for ETG evolution which is dominated by hierarchical processes.

In this thesis we explored the use of nuclear stellar discs as tracers of the merging history of early-type galaxies. These small structures, just a few tens to a few hundreds of parsecs across, are a common but poorly studied feature of early-type galaxies. They are formed during or shortly after merging events due to the infall of gas, which settles in a disc and leads to the formation of new stars. Initial simulations showed that they should not survive a following major merger and could, therefore, be used to trace the epoch when their host galaxies experienced their last major merger event. We produced the first census of nuclear discs and established that their incidence is 20%, fairly independent of the host-galaxy mass or galactic environment. Furthermore, we have more than doubled the sample of nuclear discs with known photometric properties, finding that they give a hint of possessing different characteristics from those of large, galactic discs. Using these nuclear discs as clocks for the assembly history of galaxies requires dating their stellar populations. By combining the use of integral-field spectroscopy with the a priori knowledge of the relative bulge- and disc-light contribution to the observed spectra, as determined by a photometric disc-bulge decomposition, we have shown that it is possible to reduce the degeneracies that affect the study of two superimposed populations and thus that the age of stellar discs can be measured more precisely. To illustrate our method, we present VLT-VIMOS data for NGC 4458, a low-mass slowly rotating early-type galaxy with a disc that we found to be at least 5-6 Gyr old. The presence of such an old central disc in such a small, slowly-rotating and, mostly likely, round galaxy is particularly puzzling and presents a challenge to existing models. Disc fragility is central to our studies and we have expanded the limited initial simulations to study it in more detail. By means of N-body simulations, we have reproduced the final stages of a galaxy encounter by exposing a nuclear disc rotating in the gravitational potential of its host bulge and central supermassive black hole to the impact of a secondary massive black hole. We explored not only major mergers (1:1 mass ratio), but also large minor mergers (1:5 and 1:10), across a variety of collision angles, and assessed the survival of the disc, as perceived by current observational limits, both for photometry and spectroscopy. As expected, the discs do not survive a major merger whereas it is in general possible to detect their presence after a 1:5 or 1:10 encounter, in particular when looking at kinematic signatures with spectroscopy. This thesis has demonstrated that nuclear discs constitute both a common and accurate tool for constraining the assembling history of nearby early-type galaxies. The advent of more sensitive integral-field spectrographs, such as MUSE, will make measuring the stellar age of nuclear discs not only more precise, but also more economical in terms of telescope time. This will allow embarking on a more systematic age dating campaign for nuclear stellar discs across a wider range of type, mass and galactic environments for their host galaxies. Combining such a census with a larger set of numerical simulations aimed at calibrating better the range of merger event that would erase any photometric or kinematic signature of a nuclear disc, should finally allow us to put firm constraints on the merging history of early-type galaxies.

I have investigated the properties of the large scale structure of the nearby Universe using data from the Galaxy and Mass Assembly survey (GAMA). I generated complementary halo mass estimates for all groups in the GAMA Galaxy Group Catalogue (G³C) using a modified caustic mass estimation algorithm. On average, the caustic mass estimates agree with dynamical mass estimates within a factor of 2 in 90% of groups. A volume limited sample of these groups and galaxies are used to generate the large scale structure catalogue. An adapted minimal spanning tree algorithm is used to identify and classify structures, detecting 643 filaments that measure up to 200 Mpc/h, each containing 8 groups on average. A secondary population of smaller coherent structures, dubbed `tendrils,' that link filaments together or penetrate into voids are also detected. On average, tendrils measure around 10 Mpc/h and contain 6 galaxies. The so-called line correlation function is used to prove that tendrils are real structures rather than accidental alignments. A population of isolated void galaxies are also identified. The properties of filaments and tendrils in observed and mock GAMA galaxy catalogues agree well. I go on to show that voids from other surveys that overlap with GAMA regions contain a large number of galaxies, primarily belonging to tendrils. This implies that void sizes are strongly dependent on the number density and sensitivity limits of the galaxies observed by a survey. Finally, I examine the properties of galaxies in different environments, finding that galaxies in filaments tend to be early-type, bright, spheroidal, and red whilst those in voids are typically the opposite: blue, late-type, and more faint. I show that group mass does not correlate with the brightness and morphologies of galaxies and that the primary driver of galaxy evolution is stellar mass.

We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M-*), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2 < z < 4. We do this by making new measures of M-*, SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the (M-*; SFR) plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high Sigma(1) (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of Sigma(1), which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of Sigma(1) for fixed values of M* shows two different regimes: one at the low-mass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of Sigma(1) (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.

Les amas de galaxies sont les objets gravitationnellement liés les plus massifs de l'univers, et l'histoire de leur formation est une conséquence directe de l'évolution des structures dans l'univers. Ainsi, leur étude permet de poser des contraintes cosmologiques. L'utilisation des amas en tant que sondes cosmologiques repose sur l'observation de leur contenu en matière, en particulier ordinaire, ou baryons. Ces derniers sont présents sous forme d'étoiles contenues dans les galaxies, et de gaz au sein du milieu intra-amas. Toutefois, les baryons dans les amas de galaxies sont sujets à des effets astrophysiques qui affecteront leurs propriétés. Ces effets doivent être étudiés en détail afin d'obtenir une bonne compréhension des amas et contraindre correctement les conditions ayant dicté leur formation, jusqu'à leurs propriétés actuelles.Je propose ainsi dans cette thèse une étude approfondie des baryons et de leurs effets dans les amas, des galaxies au gaz, à partir d'observations en millimétrique, optique, et rayons X.Une première partie de mon étude se concentre sur les galaxies et l'analyse de leurs propriétés à partir de données de spectroscopie optique, dans deux systèmes triples d'amas découverts par le satellite Planck. Je montre que ces deux systèmes n'apparaissent triples que suite à des effets de projection sur la ligne de visée, et sont en réalité constitués de plusieurs amas isolés se trouvant à plusieurs centaines de megaparsecs les uns des autres, exceptée une paire d'amas.De plus je montre que dans l'amas le plus distant, certaines galaxies forment encore des étoiles, contrairement aux galaxies dans les amas à plus bas redshift. Il est possible que cela marque la transition entre un régime d'intense formation stellaire dans les amas à haut redshift, et le régime de faible formation stellaire observé dans les amas à bas redshift.La suite de mon étude est dédiée à la fraction de gaz au sein des amas, en particulier afin de contraindre le biais découlant de l'hypothèse d'équilibre hydrostatique lors de la mesure de leur masse. Mal contraint, ce "biais hydrostatique", est responsable de contraintes cosmologiques biaisées à partir des amas. En utilisant des masses de gaz et des masses totales mesurées en rayons X sous l'hypothèse de l'équilibre hydrostatique, j'ai calculé la fraction de gaz de 120 amas, et ai étudié la valeur du biais hydrostatique et son évolution avec la masse et le redshift. Je montre que l'évolution du biais est dégénérée avec les paramètres cosmologiques, menant à des contraintes cosmologiques aberrantes en cas de mauvaise prise en compte de l'évolution du biais. Cependant, je montre que mes résultats dépendent de l'échantillon choisi, avec une évolution du biais différente suivant la sélection en masse et en redshift. Je montre toutefois que quelque soit la sélection de l'échantillon, mes résultats sont en accord avec un ensemble de mesures directes par d'autres méthodes, ainsi qu'avec les prédictions de simulations hydrodynamiques. Ces résultats sont néanmoins en désaccord avec la valeur de biais favorisée par des observations du fond diffus cosmologique combinées à des comptages d'amas.Enfin, j'ai combiné des données de fraction de gaz d'amas de galaxies avec des comptages réalisés à partir d'observations en ondes millimétriques. Cela m'a permis d'étudier les contraintes cosmologiques rendues possibles par cette combinaison, ainsi que les contraintes sur le biais hydrostatique. Je montre que l'ajout de données de fraction de gaz aux comptages d'amas permet de briser des dégénérescences existantes entre le biais hydrostatique et certains paramètres cosmologiques, sans a priori sur le biais.Mon travail a donc permis d'améliorer notre compréhension d'ensemble des propriétés astrophysiques des baryons dans les amas. J'ai notamment mis en évidence certains des liens entre effets astrophysiques et contraintes cosmologiques par les amas, permettant leur description fidèle et robuste<br>Galaxy clusters are the most massive gravitationally bound structures of the universe, and the history of their formation is a direct consequence of the evolution of the large scale structure of the universe. As a result, studying these objects allows to constrain cosmological parameters, which are at the core of the models describing the evolution of our universe. The use of galaxy clusters as cosmological probes relies on the observation of their matter content, and in particular their content in ordinary matter, or "baryons". Baryonic matter is mainly present under the form of stars in galaxies and of gas inside the intra-cluster medium. However, baryons in galaxy clusters are subject to astrophysical effects which will impact their properties. These effects need to be analysed in detail in order to obtain an in depth understanding of these objects and to properly constrain the conditions that dictated their formation, their assembly, and their current properties.I propose in this thesis a thorough analysis of baryons and of their effects in clusters, from galaxies to the gas, using observations in optical, X-ray, and millimeter wavelengths. A first part of my study is focused on galaxies and the analysis of their properties from optical spectroscopy, inside two triple-cluster systems discovered by the Planck satellite. I show that these two systems appear as triple only due to projection effects on the line of sight, and that they are actually constituted of isolated clusters lying at several hundreds of megaparsecs from each other, except for a cluster pair. I show in addition that inside the most distant cluster, several galaxies are still star-forming, contrary to the galaxies in lower redshift systems. This may be the sign of a transition between a regime of high star formation in high redshift systems and the low star formation regime which is observed in low redshift clusters.The remainder of my work is dedicated to the gas fraction in galaxy clusters, in particular to constrain the bias which appears following the assumption of hydrostatic equilibrium when measuring cluster masses. This "hydrostatic bias", if poorly understood, is responsible for biased cosmological constraints from galaxy clusters. By using gas masses and total masses computed under the assumption of hydrostatic equilibrium in X-ray observations, I computed the gas fraction of 120 galaxy clusters, and constrained the value of the hydrostatic bias, as well as its evolution with mass and redshift. I show that the evolution of the bias is degenerate with cosmological parameters, leading to aberrant cosmological constraints when assuming the wrong evolution for the bias. I however show that these results are dependent on the considered sample, with trends of the bias changing depending on the mass and redshift selection of the sample. In any case, whatever the sample selection I find that my results are in agreement with a collection of other measurements of the bias using other methods, as well as with predictions from hydrodynamical simulations. These results are nevertheless in tension with the value of the bias preferred by the combination of cosmic microwave background observations with galaxy cluster number counts.Finally I combined gas fraction data of clusters with cluster number counts from millimeter wavelengths observations. This allowed me to study the constraints on cosmological parameters that this combination allowed, as well as the constraints on the hydrostatic bias. I show that adding gas fraction to cluster counts allows to break degeneracies that exist between the hydrostatic bias and cosmological parameters, without any prior on the bias.My work thus allowed to improve the understanding of the astrophysical properties of baryons in galaxy clusters. I notably highlighted some of the links and correlations between astrophysical effects and cluster cosmology, allowing for an accurate and robust description of these objects

Les modèles semi-analytiques (SAMs) constituent aujourd'hui le meilleur outils d'analyse et d'étude pour la formation et l'évolution des galaxies individuels mais également des regroupements de galaxies appelés amas. Alors qu'ils reproduisent avec succès les fonctions de masse stellaire, de corrélation à deux points, de luminosité des galaxies locales (z=0), ils échouent dans les prédictions des propriétés des galaxies plus jeunes, à plus haut décalage vers le rouge. Et ce d'autant plus que la masse stellaire est faible. Ces inconsistances entre les modèles et les observations démontrent que l'histoire de l'assemblage des ces galaxies, en relation avec l'accrétion de gaz, la formation stellaire et leurs halos de matière noire n'est pas bien comprise. Dans cette thèse, nous introduisons une nouvelle version du modèle semi-analytique GalICS et nous l'utilisons pour explorer l'impact, sur la formation stellaire des galaxies à faible masse, de la rétroaction des supernovae et des trous noirs supermassifs ainsi que des processus de photo-ionisation. Ces deux mécanismes sont communément utilisés pour réduire la formation de nouvelles étoiles dans les galaxies peu massives. Nous montrons que, même appliqué avec de très fortes efficacités, ces deux processus ne peuvent pas expliquer simultanément les fonctions de masse, de luminosité et la relation entre masse stellaire et masse des halos de matière noire pour les galaxies évoluant à grand décalage spectral. Suite à ce constat, nous introduisons deux recettes ad-hoc pour la formation stellaire. Dans un premier temps nous appliquons une forte modification de l'efficacité de formation stellaire en relation directe avec la masse de matière noire de leur halo hôte. Cette première approche conduit à de bons résultats, en particulier dans le régime des faibles masses stellaires mais il présente, par construction un profond désaccord avec la loi de formation stellaire observées par Kennicutt. Pour cela, nous introduisons une seconde modification, plus profonde, basée sur l'existence d'une composante de gaz, évoluant en périphérie des premiers disques galactiques, mais ne pouvant pas, pour des raisons encore mal comprises, former de nouvelles générations d'étoiles. Progressivement, ce gaz impropre à la formation stellaire est convertit, il alimente alors la formation d'étoile. L'introduction de ce nouveau réservoir, introduit un délai entre le moment ou le gaz s'effondre au centre du halo et le moment ou ce gaz. Ce nouveau modèle donne de très bons résultats mais il pose la question de l'origine de ce gaz impropre à la formation stellaire. Nous abordons dans cette thèse quelques piste de recherche dans le cadre de la formation des grandes structures peuplant notre Univers.

Dans l'Univers local, il existe une relation très étroite entre la morphologie d'une galaxie et d'autres paramètres physiques comme, par exemple, leur cinématique intrinsèque. À grand redshift, il n'est pas clair si cette relation est toujours valide. La cinématique des galaxies est un des outils puissants pour l'étude des processus physiques qui gouvernent la formation des galaxies, en traçant les distributions intrinsèques aux galaxies de matière noire et lumineuse, et leur évolution dans le temps. Cette thèse présente le nouveau sondage HR-COSMOS, dont le but fut d'acquérir le premier échantillon statistique et représentatif de cinématique de galaxies à formation d'étoiles dans le champ profond HST/ACS COSMOS dans la plage de redshifts 0<br>In the local Universe it exists a tight relation between the galaxy morphology and other physical parameters, like the galaxy internal kinematics. At higher redshift it is not clear if this relation still exists. The galaxy kinematics is one of the best tool to study the physical processes that govern the galaxy formation, by tracing the galaxy internal distributions of luminous and dark matter and their evolution with time. This thesis presents the new survey HR-COSMOS aimed to obtain the first statistical and representative sample to study the kinematics of star-forming galaxies in the treasury HST/ACS COSMOS deep field at redshift 0

In this paper, we investigate the relationship between star formation and structure, using a mass-complete sample of 27,893 galaxies at 0.5. <. z. <. 2.5 selected from 3D-HST. We confirm that star-forming galaxies are larger than quiescent galaxies at fixed stellar mass (M*). However, in contrast with some simulations, there is only a weak relation between star formation rate (SFR) and size within the star-forming population: when dividing into quartiles based on residual offsets in SFR, we find that the sizes of star-forming galaxies in the lowest quartile are 0.27. +/-. 0.06 dex smaller than the highest quartile. We show that 50% of star formation in galaxies at fixed M. takes place within a narrow range of sizes (0.26 dex). Taken together, these results suggest that there is an abrupt cessation of star formation after galaxies attain particular structural properties. Confirming earlier results, we find that central stellar density within a 1 kpc fixed physical radius is the key parameter connecting galaxy morphology and star formation histories: galaxies with high central densities are red and have increasingly lower SFR/M., whereas galaxies with low central densities are blue and have a roughly constant (higher) SFR/M. at a given redshift. We find remarkably little scatter in the average trends and a strong evolution of > 0.5 dex in the central density threshold correlated with quiescence from z.similar to. 0.7-2.0. Neither a compact size nor high-n are sufficient to assess the likelihood of quiescence for the average galaxy; instead, the combination of these two parameters together with M* results in a unique quenching threshold in central density/velocity.

In this paper, we investigate the relationship between star formation and structure, using a mass-complete sample of 27,893 galaxies at 0.5. <. z. <. 2.5 selected from 3D-HST. We confirm that star-forming galaxies are larger than quiescent galaxies at fixed stellar mass (M*). However, in contrast with some simulations, there is only a weak relation between star formation rate (SFR) and size within the star-forming population: when dividing into quartiles based on residual offsets in SFR, we find that the sizes of star-forming galaxies in the lowest quartile are 0.27. +/-. 0.06 dex smaller than the highest quartile. We show that 50% of star formation in galaxies at fixed M. takes place within a narrow range of sizes (0.26 dex). Taken together, these results suggest that there is an abrupt cessation of star formation after galaxies attain particular structural properties. Confirming earlier results, we find that central stellar density within a 1 kpc fixed physical radius is the key parameter connecting galaxy morphology and star formation histories: galaxies with high central densities are red and have increasingly lower SFR/M., whereas galaxies with low central densities are blue and have a roughly constant (higher) SFR/M. at a given redshift. We find remarkably little scatter in the average trends and a strong evolution of > 0.5 dex in the central density threshold correlated with quiescence from z.similar to. 0.7-2.0. Neither a compact size nor high-n are sufficient to assess the likelihood of quiescence for the average galaxy; instead, the combination of these two parameters together with M* results in a unique quenching threshold in central density/velocity.

Les propriétés globales des galaxies montrent une forte évolution du taux de formation stellaire et de la densité de masse stellaire à l'époque de l'assemblage des galaxies précédent le pic de formation stellaire dans l'univers, produite par plusieurs processus physiques concurrents (fusion, accrétion, rétroaction, environnement, ...). Les propriétés morphologiques des galaxies ont aussi fortement évolué à la même époque. Dans cette thèse, j'étudie comment l'évolution des propriétés morphologique est reliée aux propriétés spectrophotométriques des galaxies depuis z ~ 6. Les données spectroscopiques obtenues au sein du VIMOS Ultra Deep Survey (VUDS), un nouveau sondage spectroscopique unique de ~ 10000 galaxies entre redshift z~2 et z~6 qui fournissent un excellent moyen de sonder l'évolution galactique à travers cette époque cosmique. A partir des mes résultats, je conclus que les différentes propriétés morphologiques de galaxies à formation stellaire aux redshifts 2<br>The global properties of galaxies show a strong evolution of the star formation rate and stellar mass density at the epoch of galaxy assembly, driven by several competing physical processes (merging, accretion, feedback, environment,...). The morphological properties of galaxies are also strongly evolving over the same timescales. I investigate how the evolution of the morphological properties is connected to the spectrophotometric properties of galaxies since z~6. The spectroscopic data obtained within the VIMOS Ultra Deep Survey (VUDS), a new unique spectroscopic survey of ~10000 galaxies between redshifts z~2 and z~6 conducted at the ESO-VLT, combined with the available Hubble Space Telescope imaging surveys such as COSMOS or CANDELS provide a great way of probing galactic evolution across this cosmic epoch.From the results that I have obtained, I conclude that the different morphological properties of star-forming galaxies at 2

Cette thèse présente la mesure des redshifts photométriques et des paramètres physiques dans le cadre des sondages de galaxies à grande échelle, ainsi que la contrainte qui peut en être extraite sur l'évolution des galaxies. Je montre notamment dans cette thèse dans quelle mesure la calibration photométrique affecte la précision des redshifts photométriques, afin de contraindre la stratégie photométrique à développer pour la mission Euclid.Afin de prendre en compte les problèmes inhérents à l'observation, les analyses ont été effectuée sur la base de données observées dont la configuration est proche de celle qui est attendue pour Euclid. Ces données combinent de nouvelles observations en proche-infrarouges conduites pour couvrir le sondage spectroscopique VIPERS et la photométrie du CFHTLS. Sur la base des conclusions tirées de cette analyse, j'ai produit le nouveau catalogue photométrique de VIPERS, ainsi que le catalogue de redshifts photométriques associé. J'ai finalement utilisée la même photométrie pour dériver les paramètres physiques d'environ 760 000 galaxies, réparties sur plus de 22 degrés carrés à une magnitude limite Ks(AB) &lt; 22. J'ai ainsi pu étudier l'évolution de la fonction de masse stellaire entre les redshifts z = 0.2 et z = 1.5. Ceci a permis de montrer que les galaxies dont la masse stellaire est d'environ log(M/Msol) = 10.66 voient généralement leur formation stellaire stoppée en 2 à 4 milliards d'années, alors que les galaxies de faible masse (log(M/Msol) &lt; 9.5) ne formant plus d'étoiles ont vu leur formation stellaire être arrêtée 5 à 10 fois plus rapidement (en environ 0.4 milliard d'années)<br>This thesis presents the measurement of the photometric redshifts and physical parameters in the framework of large scale surveys, and their constraint on galaxy evolution. The photometric redshift measurement allows us to study the entire photometric sample. For this reason, the weak lensing signal measurement used in the Euclid mission as a primary cosmological probe will rely on photometric redshift measurements. However, the method is strongly affected by the quality of the photometry. In particular, I show in this thesis how the photometric calibration impacts the photometric redshift precison, in order to constrain the photometric strategy to use in the Euclid mission.Aiming to take into account for observationnal problems, the analysis is done with observationnal data whose photometric configuration is close to the expected Euclid one. These data combine new near-infrared observations conduected to cover the VIPERS spectroscopic survey and the CFHTLS photometry.Using the conclusions of this analysis, I have producted the new photometric catalogue for VIPERS and the associated photometric redshift calalogue.Finally, I used the same photometry to compute the stellar masses of 760,000 galaxies covering 22 square degrees at the limiting magnitude Ks(AB) &lt; 22. This enabled me to study the evolution of the stellar mass function between redshifts z= 0.2 and z = 1.5. We have then shown that the star formation of galaxies with stellar masses around log(M/Msol) = 10.66 is stopped in 2-4 Gyr, while in quiescent low-mass (log(M/Msol) &lt; 9.5) galaxies, the star formation has been stopped 5-10 times faster (approximatelly in 0.4 Gyr)

This thesis is dedicated to the investigation of clustering properties of both normal and active galaxies over a wide range of redshifts, from local to z>2. These sources, selected in the infrared with Spitzer and X-rays with Chandra, represent different classes of objects in the high-z Universe - X-ray emitting AGNs at z>~1, massive evolved galaxies at z~2, and star-forming galaxies at z~=1.7 and 0.7. We report on the measurements of the correlation functions for these objects and combine them with the clustering models of dark matter halos in order to infer the halo occupation properties of the various galaxy populations. We first discuss the clustering of galaxies with signs of active star formation detected at 24 um by Spitzer. Using optical/near-IR colors, we separate the sample into a lower-redshift (<z>=0.68 and higher-redshift (<z>=1.72) galaxy populations, and measure comoving correlation lengths of r0 = 4.74+-0.16 h**{-1} Mpc and r0 =7.87+-0.63 h**{-1}Mpc, respectively. From this we derive the masses of parent dark matter halos Mtot>~2*10**12 h**{-1}Msun for the high-z population, compared to Mtot>~5*10**11 h**{-1}Msun at the lower redshifts --- in line with the estimated IR luminosities L_IR>10**12Lsun (corresponding to ``ULIRGs'') and L_IR~10**11Lsun (``LIRGs''). We then present the analysis of massive (estimated stellar mass M*~=1.6*10**11 Msun), high-redshift (<z>=2.2) galaxies previously selected by the presence of the 1.6 um stellar peak redshifted into the 5.8 um Spitzer band (``IR-peakers''). We find that the key observable characteristics of IR-peakers - their stellar mass, number density, and clustering, are best explained if they reside in those 10-25% of dark matter halos with Mtot~=[0.5-1]*10**{13}Msun, in which the star conversion efficiency reaches ~10-20%. We also show that IR-peakers can not be located only in the central galaxies of parent dark matter halos, or only in the subhalos. Finally, we measure the spatial clustering of AGNs detected by the Chandra X-ray Observatory in the Bootes field over a redshift interval from z=0.17 to z~3. The derived correlation lengths are consistent with no redshift trend within the sample. The availability of accurate spectroscopic redshifts allows us to use the two-point correlation functions projected on the sky plane and in the line of sight to show that the X-ray AGNs are predominantly located at the centers of dark matter halos with Mtot>3.7*10**12 h**{-1}Msun, and tend to avoid satellite galaxies in halos of this or higher mass. The halo occupation properties inferred from the clustering data of Chandra AGNs --- the mass scale of the parent dark matter halos, the lack of significant redshift evolution of the clustering length, and the low satellite fraction --- are broadly consistent with the scenario of quasar activity triggered by mergers of similarly-sized galaxies. Interestingly, the three classes of objects studied in this thesis have similar correlation lengths (r0~=7-8 h**{-1}Mpc), and hence reside in dark matter halos of similar mass, a few *10**12 h**{-1}Msun. However, they represent distinct and mostly non-overlapping populations. The star-forming galaxies are found in ~=20% of halos of this mass, presumably those which experienced a star formation trigger in the recent past. The very massive normal galaxies (``IR-peakers'') reside in 10-20% of the halos which had an enhanced star formation efficiency at very high redshifts. The X-ray selected AGNs occupy a small fraction ~1-5% of the halos, and we find an evidence for a difference in the clustering properties of AGNs and IR-peakers - while the latter include both massive central galaxies and satellite galaxies, the AGNs are preferentially located in the central galaxies. Taken together, the objects studied in this thesis populate ~30-50% of the massive dark matter halos at z=1-2.<br>La tesi e' dedicata allo studio delle proprieta' di clustering di galassie normali e attive, in un ampio intervallo di redshift, dall'Universo locale fino a z>2. Queste sorgenti, selezionate nell’infrarosso con Spitzer e nei raggi X con Chandra, rappresentano diverse classi di oggetti ad alto redshift - AGN a z>1 che emettono nell'X, massicce galassie evolute a z~2 e galassie con formazione stellare a z~=1.7 e 0.7. Calcoliamo alcune misure di funzioni di correlazione angolare per questi oggetti e le combiniamo con dei modelli di clustering per gli aloni di materia oscura allo scopo di inferire le proprieta' di occupazione degli aloni per le diverse popolazioni di galassie. Inizialmente si sono discusse le proprieta' di clustering delle galassie con indicazioni di attivita' di formazione stellare, rilevate a 24 um da Spitzer. Usando i colori nell'ottico/vicino-IR, abbiamo suddiviso il campione in una popolazione a basso-redshift e in (<z>=0.68) una popolazione ad alto-redshift (<z>=1.72), e abbiamo misurato una lunghezza di correlazione comovente di r0 = 4.74+-0.16h**{-1} Mpc e r_0 =7.87+-0.63 h**{-1}Mpc, rispettivamente. Da questo abbiamo potuto derivare le masse degli aloni di materia oscura Mtot>~2*10**12 h**{-1}Msun per la popolazione ad alto redshift, da confrontare con quella stimata per la popolazione a basso redshift Mtot>~5*10**11 h**{-1}Msun - in linea con le stime delle luminosita' IR L_IR>10**12Lsun(``ULIRG``) e L_IR~10**11 Lsun (``LIRG``). Si e' quindi presentata l'analisi di galassie massicce (massa stellare stimata di M*~=1.6*10**11 Msun), ad alto redshift (<z>=2.2) preliminarmente selezionate dalla presenza del picco di emissione stellare a 1.6 um, che si trova spostato alla lunghezza d'onda osservata a nella 5.8 um banda Spitzer (i cosiddetti ``IR-peakers``). Si e' trovato che le proprieta' osservate degli IR-peakers - la loro massa stellare, densita' numerica e proprieta' di clustering - sono spiegate al meglio se si assume che essi risiedano in quel 10-25% di aloni di materia oscura con Mtot~=[0.5-1]*10**13 Msun, in cui l'efficienza di conversione stellare raggiunge il ~10-20%. Si e' inoltre dimostrato che gli IR-peakers non possono trovarsi solamente nelle galassie centrali dei corrispettivi aloni di materia oscura, o solo nei sottoaloni. Infine, si e' misurato il clustering spaziale degli AGN rilevati dall'osservatorio spaziale a raggi X Chandra nel campo Bootes, in un intervallo di redshift da z=0.17 a z~3. Le lunghezze di correlazione derivate non indicano nessun andamento con il redshift, all’interno di questo campione. La disponibilita' di accurati redshift spettroscopivi ci ha permesso di utilizzare le funzioni di correlazione a due punti proiettate sul piano del cielo, e lungo la linea di vista, per mostare che gli AGN selezionati nei raggi X sono principalmente collocati nei centri degli aloni di materia oscura con Mtot>3.7*10**12 h**{-1} Msun, e tendono ad evitare galassie satelliti in aloni di masse di quest'ordine di grandezza, o maggiori. Le proprieta' di occupazione derivate dai dati di clustering degli AGN Chandra - la scala delle masse dei corrispettivi aloni di materia oscura, la mancanza di una significativa evoluzione con il redshift della lunghezza di correlazione del clustering, e la bassa frazione di satelliti - sono in linea di massima consistenti con lo scenario dell'attivita' di quasar attivata dai \textit{mergers} di galassie di massa simile. Di particolare interesse, si e' trovato che le tre classi di oggetti studiate in questa tesi hanno una lunghezza di correlazione simile (r0~=7-8 h**{-1} Mpc), e quindi risiedono in aloni di materia oscura di massa comparabile, alcuni*10**12 h**{-1}Msun. Tuttavia, essi rappresentano delle popolazioni distinte e largamente non sovrapposte. Le galassie star-forming si trovano nel ~=20% degli aloni di questa massa, probabilmente quelli che hanno subito un innescamento della formazione stellare nel passato recente. Le galassie normali molto massicce (``IR-peakers``) risiedono nel 10-20% degli aloni che hanno avuto un aumento dell’efficienza della formazione stellare a redshift molto alti. Gli AGN selezionati nei raggi X occupano una piccola frazione (~ 1-5%) degli aloni, e si e' trovata evidenza di una differenza nelle proprieta' di clustering di AGN ed IR-peakers: mentre questi ultimi includono sia galassie centrali massicce e galassie satellite, gli AGN sono preferenzialmente situati nelle galassie centrali. Considerati insieme, gli oggetti studiati in questa tesi popolano il ~30-50% degli aloni di materia oscura piu' massicci fra z=1 e z=2.

Galaxy clusters, the massive systems host hundreds of galaxies, are invaluable cosmological probes and astrophysical laboratories. Besides these fascinating galaxies, the concentration of dark matter creates a deep gravitational potential well, where even light passing by is bended and the background image is distorted. The baryonic gas falling into the potential well is heated up to more than 10^7 K that free electrons start to emitting in X-ray. Observing those phenomena leads to a throughout understanding of gravity, particle physics and hydrodynamics. In addition, residing on the top of the density perturbations, clusters are sensitive to the initial condition of the Universe, such that they are complimentary tools for cosmology studies. In this thesis we first introduce the basic framework of the Universe and supporting observational evidence. Following that, we sketch the principle to use clusters for cosmology study via their redshift and mass distribution. However cluster mass is not a direct observable, so we need to estimate it by other channels. We briefly exhibit cluster observations in optical, X-ray and microwave bands and discuss the challenges in estimating the underlying cluster mass with them. After this introduction, we present our results on three aspects of the cluster cosmology study. First, we present a study of Planck Sunyaev-Zel’dovich effect (SZE) selected galaxy cluster candidates using Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) imaging data. To fulfil the strength of SZE survey, the redshifts of clusters are required. In this work we examine 237 Planck cluster candidates that have no redshift in the Planck source catalogue. Among them, we confirmed 60 galaxy clusters and measure their redshifts. For the remaining sample, 83 candidates are so heavily contaminated by stars due to their location near the Galactic plane that we do not identify galaxy members and assign reliable redshifts. For the rest 94 candidates we find no optical counterparts. By examining with 150 Planck confirmed clusters with spectroscopy redshifts, our redshift estimations have an accuracy of σ_{z/(1+z)}~0.022. Scaling for the already published Planck sample, we expect the majority of the unconfirmed candidates to be noise fluctuations, except a few at high redshift that the Pan-STARRS1 (PS1) data are not sufficiently deep for confirmation. Thus we use the depth of the optical imaging for each candidate together with a model of the expected galaxy population for a massive cluster to estimate a redshift lower limit, beyond which we would not have expected to detect the optical counterpart. Second, we use 95GHz, 150GHz, and 220GHz observations from South Pole Telescope (SPT) to study the SZE signatures of a sample of 46 X-ray selected groups and clusters drawn from ~6 deg^2 of the XMM-Newton Blanco Cosmology Survey (XMM-BCS). The wide redshift range and low masses make this analysis complementary to previous studies. We develop an analysis tool that using X-ray luminosity as a mass proxy to extract selection-bias corrected constraints on the SZE significance- and Y_{SZ}-mass relations. The SZE significance- mass relation is in good agreement with an extrapolation of the relation obtained from high mass clusters. However, the fit to the Y_{SZ}-mass relation at low masses, while in agreement with the extrapolation from high mass SPT sample, is in tension at 2.8σ with the constraints from the Planck sample. We examine the tension with the Planck relation, discussing sample differences and biases that could contribute. We also analyse the radio galaxy point source population in this ensemble of X-ray selected systems. We find 18 of our systems have 1 GHz Sydney University Molonglo Sky Survey (SUMSS) sources within 2 arcmin of the X-ray centre, and three of these are also detected at significance >4 by SPT. Among these three, two are associated with the brightest cluster galaxies, and the third is a likely unassociated quasar candidate. We examined the impact of these point sources on our SZE scaling relation result and find no evidence of biases. We also examined the impact of dusty galaxies. By stacking the 220 GHz data, we found 2.8σ significant evidence of flux excess, which would correspond to an average underestimate of the SZE signal that is (17±9) % in this sample of low mass systems. Finally we predict a factor of four to five improvements on these SZE mass-observable relation constraints based on future data from SPTpol and XMM-XXL. In the end we present a study using clusters as tools to probe deviations from adiabatic evolution of the Cosmic Microwave Background (CMB) temperature. The expected adiabatic evolution is a key prediction of standard cosmology. We measure the deviation of the form T(z)=T_0(1+z)^{1-α} using measurements of the spectrum of the SZE with SPT. We present a method using the ratio of the SZE signal measured at 95 and 150 GHz in the SPT data to constrain the temperature of the CMB. We validate that this approach provides unbiased results using mock observations of cluster from a new set of hydrodynamical simulations. Applying this method to a sample of 158 SPT-selected clusters, we measure α=0.017^{+0.030}_{−0.028} consistent with the standard model prediction of α=0. Combining with other published results, we find α=0.005±0.012, an improvement of ~ 10% over published constraints. This measurement also provides a strong constraint on the effective equation of state, w_{eff}=−0.994±0.010, which is presented in models of decaying dark energy.

En tant que structures liées les plus massives de l’univers, les amas de galaxies permettent d’étudier l’influence de l’environnement sur l’évolution des galaxies. Dans ce manuscrit, je présente AMASCFI, un algorithme de détection d’amas développé durant la thèse et utilise le catalogue d’amas obtenu à partir des décalages spectraux photométriques du relevé Canada France Hawaii Telescope Legacy Survey (CFHTLS) pour étudier le rôle des amas sur l’évolution des galaxies. Je démontre les bonnes performances d’AMASCFI sur Euclid et le CFHTLS à partir de données simulées. Je l’applique au CFHTLS pour lequel AMASCFI est pur à 90% et complet à 70% à z&lt;0.7 et déduis une masse pour chaque amas détecté à partir de la richesse. J’étudie alors l'évolution en décalage spectral des fonctions de luminosité des galaxies (GLF) de type précoce (ETG) et de type tardif (LTG) à différentes masses d’amas. J’observe que la GLF des ETGs faibles décroît à grand décalage spectral, la séquence rouge (RS) étant déjà formée à z~0.7, mais enrichie par de faibles ETG à z&lt;0.7. Cela peut être dû à la suppression de la formation stellaire (“quenching”) des LTG dans l’amas ou à l'accrétion de faibles ETG pré-traités dans des groupes en chute sur l’amas. Pour étudier le rôle de ce pré-traitement, je détecte les filaments de la toile cosmique avec la méthode de Laigle et al (2018) et montre qu’elle est bien valide à la précision du CFHTLS. En comparant les distances aux amas AMASCFI des ETG et des LTG dans les filaments, je conclue que les filaments doivent être le siège de “quenching”. Cela pourrait être dû à l’étranglement des galaxies dans les groupes de galaxies mais plus de preuves sont nécessaires<br>As the most massive bound structures in the universe, galaxy clusters are a powerful probe of the impact of environment on galaxy evolution. In this work, I present AMASCFI, a new cluster finder algorithm using photometric redshifts I developed during the PhD and use the cluster catalogue obtained on the Canada France Hawaii Telescope Legacy Survey (CFHTLS) to investigate the role played by clusters and their environment on galaxy evolution. We show the good performances of AMASCFI on Euclid and the CFHTLS using mock data. In particular AMASCFI is 90% pure and 70% complete to z&lt;0.7 for the latter. We then apply AMASCFI to the CFHTLS T0007, and infer a mass for each detected cluster using richness as a proxy. Using our cluster catalogue, we study the redshift evolution of the galaxy luminosity functions (GLFs) of early-type (ETGs) and late-type (LTGs) galaxies at different cluster masses. We observe that the ETG GLF faint-end drops at high redshift, the red sequence (RS) being already formed at z~0.7, but enriched by faint ETGs at z&lt;0.7. This could be due to quenching of LTGs in the cluster or accretion of faint ETGs pre-processed in infalling groups. To investigate the role of pre-processing, we use the method of Laigle et al (2018) to detect filaments from photometric redshifts and show that it allows to recover the 3D cosmic web at CFHTLS accuracy. We apply it to the CFHTLS and detect filaments around AMASCFI clusters. Studying the distances of ETGs and LTGs in these filaments to clusters, we conclude that some quenching occurs in filaments. We suggest that this might be due to strangulation in galaxy groups though we still lack conclusive evidence for such a mechanism

La composante baryonique de la structure à grande échelle de l’Univers est composée de concentration de gaz et de galaxies, donnant lieu à des groupes, à des amas, à des filaments allongés et à des murs étendus. Ces structures peuvent suivre la distribution de matière noire dans l’Univers. Néanmoins, selon le modèle cosmologique actuel, l’ensemble des matières baryoniques dans l’Univers n’a pas encore été observé. Cependant, les simulations numériques nous suggèrent qu’entre la moitié et deux tiers des parties des baryons sont localisées entre les amas de galaxies et peuplent les structures qui les relient. Les structures les plus concentrées, que nous appelons ici « des systèmes » (i.e. groupes et amas), ont généralement des gaz à haute concentration et une température élevée (1 - 10 keV). Cette température se refroidit en émettant des photons qui sont observables en rayons X. De plus les gaz interagissent avec les photons du fond diffuse cosmologique par l’effet Sunyaev–Zel'dovich (SZ) , observable à longueur d’onde millimétrique. Dans les filamentaires et murs qui sont des structures moins denses, les baryons sont probablement dans un état moins dense et à une température modérée (0.01 - 1 keV). Ces gaz tièdes sont appelés WHIM (Warm Hot Intergalactic Medium). Pendant cette Thèse de doctorat nous étudions les effets environnementaux associés aux différents composants de la structure à grande échelle de l’Univers. Pour les systèmes, l'objectif est la caractérisation du milieu intra amas en utilisant l’effet SZ. Pour cela nous utilisons les observations du satellite Planck et de l’Atacama Cosmological Télescope (ACT) afin d’analyser les profils de pression pour un échantillon d’amas de faible masse. D'autre part, pour l'étude des structures à faible densité (structures filamentaires). Nous avons construit un échantillon de candidats à filaments, cet échantillon se compose des chaînes d’amas reliées en une structure de super amas de galaxies. Notre objectif est de prouver leur nature filamentaire et de caractériser ses composants (galaxies, amas et gaz)<br>The baryonic component of the Large Scale Structure (LSS) of the Universe is composed by concentrations of gas and galaxies forming groups, clusters, elongated filaments and widely spread sheets which probably underline the distribution of dark matter. Nevertheless, according to the current cosmological models, most of the baryonic material in the Universe has not yet been directly observed. Numerical simulations suggest that from one-half to two-thirds of all baryons may be located out of clusters of galaxies, pervading the structures between them. The most concentrated structures, which we call systems of galaxies (i.e., groups and clusters) usually contain high density hot gas (1 - 10 keV) that cools radiatively, emits at X-rays wavelengths and interacts with the cosmic microwave background at millimeter wavelengths (Sunyaev Zel'dovich effect, SZ). For the less dense structures, filaments and sheets, the baryons are probably in moderately hot gas phase (0.01 - 1 keV), commonly named as warm hot intergalactic medium (WHIM). In this PhD Thesis, we study the environmental effects associated to the different components of the LSS. For the galaxy systems, we aim to characterize the intra cluster medium (ICM) through the analysis of the S-Z effect. We employ the ACT and Planck data to analyze the gas pressure profiles of a sample of low mass galaxy clusters. For the least dense structures, we assembled a sample of filament candidates composed by chains of clusters that are located inside superclusters of galaxies. We aim to probe the filament structure skeletons and characterize their components (galaxies, groups/clusters and gas)

Durant les trois dernières décennies, la cosmologie et le paradigme de la matière noire ont été étudiés grâce au développement des simulations cosmologiques à N-corps et, parallèlement, à l'acquisition de nouvelles données observationnelles impressionnantes (WMAP, SDSS, HST). Durant mon travail de thèse, j'ai étudié les structures internes des halos de matière noire des galaxies provenant des simulations numériques par une nouvelle méthode appliquée à l'espace des phases à six dimensions. Dans un premier temps, j'ai évalué différentes méthodes utilisées pour l'estimation de la densité de l'espace des phases comme la tessellation de Delaunay, les méthodes SPH et d'autres encore. En particulier, j'ai montré les avantages des analyses de la densité de l'espace des phases par rapport aux estimations de densité 3D habituelles. J'ai étudié différentes méthodes pour résoudre le problème de mise à l'echelle entre l'espace des vitesses et celui des positions comme l'emploi du critère d'entropie locale. Dans un deuxième temps, j'ai implémenté un nouveau chercheur hiérarchique de structures (HSF en anglais) multi-dimensionnel en introduisant des critères de coupe et de croissance originaux pour séparer efficacement les différentes structures dans l'espace des phases. J'ai passé en revue ses avantages et inconvénients par rapport aux algorithmes actuellement utilisés en analysant un large halo dans la Simulation Millenium. J'ai ensuite étudié les propriétés dynamiques et physiques des structures trouvées par mon algorithme. J'ai trouvé de nouvelles classes de structures tels que les queues de marée et les courants locaux, ce qui est très important dans le contexte cosmologique.

Ce travail de thèse présente plusieurs études qui utilisent la spectroscopie à haute résolution pour déterminer les propriétés chimiques des différentes populations stellaires de la Voie Lactée. Le document est structuré comme suit : Le premier chapitre de la thèse, divisée en 3 sections, est une introduction générale à la structure de la Voie lactée et à ses populations stellaires, suivie d'une partie décrivant les différentes méthodes utilisées pour mesurer les abondances chimiques des étoiles. La première section décrit les différents scénarios concernant la structure et la formation de la Voie Lactée, en présentant en particulier les découvertes les plus récentes. La deuxième section introduit les concepts physiques de base nécessaires et les objectifs des études présentes dans ce travail de thèse. La troisième section décrit les méthodes utilisées dans l'analyse des données spectroscopiques.Le deuxième chapitre présente les travaux effectués dans la cadre du projet MINCE. La première étude concerne l'analyse de la composition chimique d'un échantillon d'étoiles géantes jeunes qui ont été découvertes par hasard au cours des premières missions d'observations du projet MINCE. J'ai déterminé les paramètres stellaires, analysé les spectres, mesuré les vitesses de rotation de ces étoiles et comparé les résultats aux modèles théoriques, en reportant tous ces résultats dans un article. La deuxième étude présente les résultats obtenus par l'analyse du premier échantillon d'étoiles propres au projet MINCE. J'ai contribué à l'analyse d'une partie des spectres stellaires de ce tout premier jeu de spectres MINCE.Le troisième chapitre porte sur les résultats d'une analyse faite dans le contexte du projet CERES. La première partie de ce travail présente une détermination détaillée de la composition chimique de l'étoile RAVE J110842.1-715300, dont le but est de savoir si cette étoile provient de l'amas globulaire Omega Centauri. Ma contribution porte sur la détermination des paramètres stellaires de cette étoile. La deuxième étude menée dans le contexte de ce projet CERES est constituée de l'analyse d'un échantillon d'étoiles. J'ai déterminé les paramètres stellaires, calculé les modèles d'atmosphère et les abondances chimiques, et écrit l'article. Le quatrième chapitre porte sur un travail fait dans le contexte du projet "High-speed stars" s'intéressant aux étoiles à grande vitesse transversales héliocentriques (&gt;= 500 km/s). La première étude porte sur le suivi spectroscopique à haute résolution de deux étoiles jeunes et pauvres en métaux de l'échantillon de Caffau et al. (2020), afin de déterminer si ces étoiles sont des "blue stragglers". J'ai obtenu et analysé les spectres UVES de ces deux étoiles. Les résultats ne sont pas encore publiés. La deuxième étude concerne une analyse détaillée de deux étoiles à grande vitesse observées avec le spectrographe HDS au télescope Subaru. Pour cette étude, j'ai déterminé l'abondance du Carbone.Le cinquième chapitre présente les résultats obtenus à partir de l'analyse d'un échantillon d'étoiles sélectionnées au moyen de la photométrie de PRISTINE. La première étude porte sur la détermination de la composition chimique d'un échantillon d'étoiles qui ont pu être enrichies par les éjectae de l'explosion de supernovae à instabilité de paires. Mon travail a consisté à sélectionner les candidats les plus intéressants, puis d'effectuer une mission d' observation avec le spectrographe SOPHIE à l'Observatoire de le Haute Provence (OHP). La deuxième étude présente les résultats préliminaires de la détermination de la composition chimique d'un échantillon d'étoiles Pristine sélectionnées comme extrêmement pauvres en métaux. Mon travail a porté sur la détermination des paramètres stellaires et le calcul des abondances chimiques. Un article est en préparation.Le sixième chapitre présente les conclusions de ce travail de thèse et apporte quelques reflexions sur les projets à venir<br>This thesis project presents several studies that are focused on the investigation of the chemical properties of different stellar populations in the Milky Way by means of high-resolution spectroscopy.The thesis is structured as follows:The first chapter is an introduction to the thesis project, and is divided into three sections. The first section describes the structure and formation scenarios of the Milky Way, in particular by referring to the most recent discoveries. The second section introduces the basic concepts and objectives of the studies presented in this thesis work. The third section describes the methods used to analyse the spectroscopic data.The second chapter presents the studies carried out in the context of the MINCE project. The first study is devoted to the chemical analysis of a sample of young giant stars that was serendipitously discovered during the first MINCE observations. My contribution in this work was to derive the stellar parameters, analyse the spectroscopic data, measure the rotational velocities, compare the results with theoretical models and write the paper. The second study presents the results obtained from the analysis of the first sample of MINCE stars. In this work, I contributed to the analysis of some of the stars in the sample.The third chapter presents the results obtained in the context of the CERES project. The first study presents a detailed chemical analysis of the star RAVE J110842.1-715300, with the aim of understanding whether or not it originated in the Omega Centauri globular cluster. My contribution in this study was to derive the stellar parameters of the star. The second study presents the results obtained for the CERES star sample. My contribution was to derive the parameters, compute model atmospheres, measure the chemical abundances, and write the paper.The fourth chapter presents the results obtained in the context of the High-speed stars project. The first study reports the results obtained from the high-resolution follow-up of two young and metal-poor stars in the sample of Caffau et al. (2020), to check whether they are blue stragglers or not. My contribution in this study was to obtain the high-resolution observations with UVES and to analyse the data. These results have not been published yet. The second study presents a detailed analysis of two high-speed stars observed with Subaru. In this study I was involved in the C abundance determination.The fifth chapter presents the results obtained from the chemical analysis of samples of stars selected using the Pristine photometry. The first study presents the chemical analysis of a sample of metal-poor stars that may have been enriched by the explosion of pair instability supernovae. My contribution was to select promising candidates and observe them with the SOPHIE spectrographat Observatoire de le Haute Provence (OHP)in visitor mode. The second study presents the preliminary results obtained from the chemical analysis of a sample of Pristine extremely metal-poor candidates. My contribution in this study was to derive the stellar parameters and the chemical abundances. The paper is in preparation.The sixth chapter concludes the thesis and gathers final reflections and future projects

This thesis presents one of the first census of the properties of galaxies in X-ray selected groups and clusters at intermediate redshift, with the aim of assessing the role of envi- ronment on the galaxy stellar mass assembly, star formation activity and observed stellar population properties. My project is framed in the XXL Survey (Pierre et al. 2016), the largest XMM-Newton programme approved to date, covering two extragalactic regions in the sky of 25 deg2 each one. Extended X-ray sources identified as groups and clusters are spectroscopically confirmed and their main properties are characterised either via direct measurements or by means of scaling relations. Among them, inferred X-ray luminosities and temperatures, virial masses and radii are of fundamental importance for the development of this thesis. The great advantage of XXL is that the XXL-North field (XXL-N) is fully covered by photometric and spectroscopic observations coming from the most recent extragalactic surveys of galaxies. The availability of such a treasure trove of information motivates the development of my research on galaxy populations at 0.1≤z≤0.6 in XXL-N, exploring the most diverse environments ranging from the field, to groups, clusters and superclusters. The first task of my work consists in the creation of a homogeneous spectrophotometric sample of galaxies, released in Guglielmo et al. (2017), suitable for scientific purposes. The catalogue contains spectroscopic redshifts, membership information on groups and clus- ters, spectroscopic completeness weights as a function of position in the sky and observed magnitude, stellar masses and absolute magnitudes computed by means of a spectral en- ergy distribution (SED) technique. The catalogue is fundamental for all XXL studies that aims at relating optical properties derived from galaxies with X-ray information and is widely used in the whole XXL collaboration. The released spectrophotometric catalogue enables the first scientific achievement of this thesis regarding the study of the galaxy stellar mass function (GSMF). The goal of this analysis is to unveil whether the mass assembly of galaxies depends on global environment, i.e. field vs groups and clusters and, among groups and clusters, on X-ray luminosity, used as a proxy for the halo mass. I performed the analysis in four redshift bins in the range 0.1≤z≤0.6, finding overall that environment does not affect the GSMF, at least in the mass range probed. The result is further confirmed by the invariance of the mean mass of member galaxies on X-ray luminosity. I also looked into the evolution of the mass assembly from z=0.6 down to z=0.1, finding that the high mass end is already in place at the oldest epoch and does not evolve and detecting an increase in the low-mass galaxy population in the same redshift range. This study is one of the first systematic studies on the GSMF conducted for X-ray extended sources ranging from the group to the cluster environment, and is published in the second part of Guglielmo et al. (2017). Having assessed the independence of the mass distributions on the global environment, I proceed investigating whether and to what extent the environment affects the star formation activity and the observed properties of the galaxy stellar populations. I started this analysis from the richest supercluster identified in XXL-N, XLSSsC N01, located at redshift z∼0.3 and composed of 14 groups and clusters. This work has been submitted in Guglielmo et al. (2018a). With focus on the region surrounding XLSSsC N01, I divided galaxies in different environments, ranging from the virial regions of groups and clusters to the field, using a combination of global and local environment parametri- sations. The main results of this study are that, in the supercluster environment, while the star forming fractions and quenching efficiency strongly depend on environment, the SFR-mass relation does not. The star forming fraction progressively declines from the field to filaments to the virialised regions of groups and clusters, with an interesting en- hancement in the outer regions of the X-ray structures. Moreover, while the average luminosity weighted (LW)-age-mass relation is independent of the environment, a clear signature for recent star formation quenching is found in the stellar ages of passive galaxies in the virialised regions of X-ray structures. Finally, I extend the analysis of this peculiar supercluster to the whole XXL-N field. This work will be enclosed in two articles in preparation (Guglielmo et al. 2018 b,c in prep.). Thanks to the higher statistics of the entire sample, I investigated the properties of galaxies and their evolution at 0.1≤z≤0.5 in different environments, with the goal of characterising the changing in the stellar population properties and the build up of the passive population via environmental quenching. Besides distinguishing among galaxies in the field, and in groups and clusters (virial regions and outskirts), I also focused on galaxies located in structures of different X-ray luminosity and in galaxies located within superclusters. Simultaneously, I also investigated the properties of galaxies located at different projected local densities (LD). In particular, I characterised the fraction of star forming/blue galaxies and of the SFR- mass relation, as a function of both global and local environment. The fraction of star forming and blue galaxies is strictly related to the environment, having the lowest value in the virial regions of groups and clusters, and the highest in the field. In outer members, the same fraction is similar to that in the field at z≥0.2, and assumes intermediate values with respect to virial members and the field at 0.1≤z<0.2. The SFR-mass relation is also environment dependent, and in particular the number of virial member galaxies having reduced SFR (galaxies in transition) nearly doubles that of field galaxies. Again, outer members show intermediate properties: the fraction of galaxies in transition is similar to the virial population at z>0.3, when it is found to be associated to the supercluster environment, and then reduces to values typical of field galaxies at 0.1≤z<0.3. The star forming and blue fractions also decrease with increasing LD at all redshifts. On the contrary, the fraction of galaxies in transition does not vary in the same LD range. These significant differences emerging among the global and local environments are intrinsically related to the different physical meaning of the two parametrisations, thus to the different physical mechanisms acting on galaxies when bound in the potential well of a dark matter halo (according to the global definition) or when exposed to interactions with other galaxies in over dense and highly populated regions (according to the local definition). During the first stages of my PhD, I also completed the analysis of my master thesis, and I report the full text of the published paper in the Appendix of the thesis (Guglielmo et al. 2015). The results are closely related to the scientific questions tackled in my PhD project, addressed through a complementary approach that reconstructed the star formation history of low- redshift galaxies in clusters and in the field to study the dependence on global environment, stellar mass and observed morphology.<br>Questa tesi presenta uno dei primi censimenti delle proprietà delle galassie in gruppi ed ammassi selezionati nei raggi X a redshift intermedio, con lo scopo di valutare il ruolo dell'ambiente sull'assemblamento della massa stellare delle galassie, l'attività di formazione stellare e le proprietà delle popolazioni stellari osservate. Il mio progetto è inquadrato nella Survey XXL (Pierre et al., 2016), il più grande programma XMM-Newton approvato fino ad oggi, che copre due regioni extra-galattiche di 25 gradi quadrati ciascuna. Le sorgenti di raggi X estese ed identificate come gruppi ed ammassi sono state confermate spettroscopicamente e le loro proprietà principali sono caratterizzate o tramite misurazioni dirette o mediante relazioni di scala. Tra queste, le luminosità e le temperature X, le masse virali ed i raggi viriali sono di fondamentale importanza per lo sviluppo di questa tesi. Il grande vantaggio di XXL è che il campo XXL-Nord (XXL-N) è completamente coperto da osservazioni fotometriche e spettroscopiche provenienti dalle più recenti survey extra-galattiche di galassie. La disponibilità di una tale miniera di informazioni motiva lo sviluppo della mia ricerca sulle popolazioni di galassie nell'intervallo di redshift 0.1≤z≤0.6 nel campo XXL-N, esplorando gli ambienti più diversi dalle regioni di campo, ai gruppi, agli ammassi e ai superammassi. Il primo compito del mio lavoro consiste nella creazione di un campione spettrofotometrico omogeneo di galassie, pubblicato in Guglielmo et al. (2017), e adatto ad essere utilizzato in un'analisi scientifica. Il catalogo contiene redshift spettroscopici, informazioni sull'appartenenza a gruppi e ammassi, pesi di completezza spettroscopica in funzione della posizione nel cielo e magnitudine osservata, le masse stellari e le magnitudini assolute calcolate mediante una tecnica di spectral energy distribution (SED). Il catalogo è fondamentale per tutti gli studi all'interno della collaborazione XXL che mirano a correlare le proprietà ottiche derivate dalle galassie con informazioni sulle strutture X ed è ampiamente utilizzato nell'intera collaborazione XXL. Il catalogo spettrofotometrico pubblicato consente il primo risultato scientifico di questa tesi riguardante lo studio della funzione di massa stellare delle galassie (GSMF). L'obiettivo di questa analisi è di svelare se il processo di assemblamento della massa delle galassie dipende dall'ambiente cosiddetto globale, cioè dall'appartenenza al campo o a gruppi ed ammassi e, tra quest'ultimi, dalla luminosità X, utilizzata come proxy per la massa di alone. Ho eseguito l'analisi in quattro intervalli di redshift nel range 0.1≤z≤0.6, trovando nel complesso che l'ambiente non influenza la GSMF, almeno nell'intervallo di massa campionato. Il risultato è ulteriormente confermato dall'invarianza della massa media delle galassie membre rispetto alla luminosità X. Ho anche esaminato l'evoluzione della GSMF da z = 0.6 fino a z = 0.1, trovando che l'estremità della funzione a masse elevate è già formata nell'epoca più antica e non evolve, e rilevando invece un aumento del numero di galassie a bassa massa nello stesso intervallo di redshift. Questo studio è uno dei primi studi sistematici della GSMF condotto per sorgenti estese a raggi X che vanno da masse di alone tipiche di gruppi fino agli ammassi, ed è pubblicato nella seconda parte di Guglielmo et al. (2017). Avendo valutato l'indipendenza delle distribuzioni di massa rispetto all'ambiente globale, procedo a indagare se e in che misura l'ambiente influisce sull'attività di formazione stellare e sulle proprietà osservate delle popolazioni stellari delle galassie. Ho iniziato questa analisi dal superammasso più ricco identificato in XXL-N, XLSSsC N01, situato a redshift z~0.3 e composto da 14 gruppi ed ammassi. Questo lavoro è stato sottomesso in Guglielmo et al. (2018a). Concentrandosi sulla regione che circonda XLSSsC N01, ho diviso le galassie in diversi ambienti, che vanno dalle regioni virali di gruppi ed ammassi fino al campo, utilizzando una combinazione di parametrizzazioni ambientali globali e locali. I risultati principali di questo studio sono che, nell'ambiente del superammasso, mentre la frazione di galassie che formano stelle e l'efficienza di arresto dell'attività di formazione stellare dipendono fortemente dall'ambiente, lo stesso non vale per la relazione fra massa e tasso di formazione stellare (SFR). La frazione di galassie che formano stelle declina progressivamente dal campo ai filamenti fino alle regioni virializzate di gruppi ed ammassi, con un interessante aumento della stessa nelle regioni esterne delle strutture X. Inoltre, mentre la relazione media fra l'età delle galassie pesata per la luminosità (LW-age) e la massa stellare delle stesse è indipendente dall'ambiente, una chiara evidenza di una recente estinzione della formazione stellare si rileva nelle galassie passive situate nelle regioni virializzate delle strutture X. Infine, si estende l'analisi di questo particolare superammasso all'intero campo XXL-N. Questo lavoro sarà racchiuso in due articoli in preparazione (Guglielmo et al., 2018 b, c in preparazione). Grazie alla statistica più elevata dell'intero campione, ho studiato le proprietà delle galassie e la loro evoluzione nell'intervallo 0.1≤z≤0.5 in diversi ambienti, con l'obiettivo di caratterizzare il cambiamento nelle proprietà delle popolazioni stellari e la formazione della popolazione passiva al variare dell'ambiente. Oltre a distinguere tra le galassie di campo, e in gruppi ed ammassi (regioni virali e periferiche), mi sono concentrata anche su galassie situate in strutture di diversa luminosità X e sulle galassie situate all'interno di superammassi. Contemporaneamente, ho anche studiato le proprietà delle galassie situate a diverse densità locali proiettate (LD). In particolare, ho caratterizzato la frazione galassie con formazione stellare attiva / galassie blu e ho studiato la relazione fra massa e SFR, in funzione sia dell'ambiente globale che di quello locale. La frazione di galassie con formazione stellare attiva e di galassie blu è strettamente correlata all'ambiente, con il valore più basso nelle regioni virali di gruppi ed ammassi e il più alto nel campo. Nei membri esterni, la stessa frazione è simile a quella nel campo a z≥0.2 e assume valori intermedi rispetto ai membri virali e il campo a 0.1≤z<0.2. La relazione fra SFR e massa è anch'essa dipendente dall'ambiente, e in particolare il numero di galassie dei membri virali che hanno una ridotta SFR (galassie in transizione) risulta essere quasi il doppio di quella di galassie di campo. Ancora una volta, i membri esterni mostrano proprietà intermedie: la frazione di galassie in transizione è simile alla popolazione virale a z>0,3, ed in particolare risulta associata all'ambiente dei superammassi, e si riduce successivamente a valori tipici delle galassie di campo a 0.1≤z<0.3. Inoltre, la frazione di galassie attive nella formazione stellare e quella di galassie blu diminuiscono con l'aumentare della LD a tutti i redshift. Al contrario, la frazione di galassie in transizione non varia nello stesso intervallo LD. Queste differenze significative emergenti tra gli ambienti globali e locali sono intrinsecamente correlate al diverso significato fisico delle due parametrizzazioni, quindi ai diversi meccanismi fisici che agiscono sulle galassie quando sono legate al potenziale gravitazionale di un alone di materia oscura (secondo la definizione globale) o quando esposto ad interazioni con altre galassie in regioni densamente popolate (secondo la definizione locale). Durante le prime fasi del mio dottorato di ricerca, ho anche completato l'analisi della mia tesi magistrale, e riporto il testo completo del documento pubblicato in Appendice alla tesi (Guglielmo et al., 2015). I risultati sono strettamente correlati alle domande scientifiche trattate nel mio progetto di dottorato, ma vengono affrontate attraverso un approccio complementare, che mira alla ricostruzione della storia della formazione stellare delle galassie a basso redshift in ammassi e nel campo per studiare la dipendenza dall'ambiente globale, dalla massa stellare e dalla morfologia osservata.

In this thesis, we aim to further elucidate the phenomenon of galaxy evolution in the environment of galaxy clusters using the methodology of numerical simulations. For that, we have developed hydrodynamic models in which idealized gas-rich galaxies move within the ICM of idealized galaxy clusters, allowing us to probe in a detailed and controlled manner their evolution in this extreme environment. The main code used in our simulations is RAMSES, and our results concern the changes in gas composition, star formation rate, luminosity and color of infalling galaxies. Additionally to processes taking place inside the galaxies themselves, we have also described the dynamics of the gas that is stripped from those galaxies with unprecedented resolution for simulations of this nature (122 pc in a box including an entire 1e14 Msun cluster), finding that clumps of molecular gas are formed within the tails of ram pressure stripped galaxies, which proceed to live in isolation within the ICM of a galaxy cluster for up to 300 Myr. Those molecular clumps possibly represent a new class of objects; similar objects have been observed in both galaxy clusters and groups, but no comprehensive description of them has been given until now. We additionally create a hydrodynamic model for the A901/2 multi-cluster system, and correlate the gas conditions in this model to the locations of a sample of candidate jellyfish galaxies in the system; this has allowed us to infer a possible mechanism for the generation of jellyfish morphologies in galaxy cluster collisions in general.<br>Nesta tese, nós visamos a contribuir para o entendimento do fenômeno da evolução de galáxias no ambiente de aglomerados de galáxias usando a metodologia de simulações numéricas. Para isso, desenvolvemos modelos hidrodinâmicos nos quais galáxias idealizadas ricas em gás movem-se em meio ao gás difuso de aglomerados de galáxias idealizados, permitindo um estudo detalhado e controlado da evolução destas galáxias neste ambiente extremo. O principal código usado em nossas simulações é o RAMSES, e nossos resultados tratam das mudanças em composição do gás, taxa de formação estelar, luminosidade e cor de galáxias caindo em aglomerados. Adicionalmente a processos acontecendo dentro das próprias galáxias, nós também descrevemos a dinâmica do gás que é varrido dessas galáxias com resolução sem precedentes para simulações dessa natureza (122 pc em uma caixa incluindo um aglomerado de 1e14 Msun inteiro), encontrando que aglomerados de gás molecular são formados nas caudas de galáxias que passaram por varrimento de gás por pressão de arraste, aglomerados estes que procedem a viver em isolamento em meio ao gás difuso de um aglomerado de galáxias por até 300 Myr. Esses aglomerados moleculares possivelmente representam uma nova classe de objetos; objetos similares foram previamente observados tanto em aglomerados quanto em grupos de galáxias, mas um tratamento compreensivo deles não foi apresentado até agora. Nós adicionalmente criamos um modelo hidrodinâmico para o sistema multi-aglomerado A901/2, e correlacionamos as condições do gás nesse modelo com a localização de uma amostra de galáxias jellyfish nesse sistema; isso nos permitiu inferir um possível mecanismo para a geração de morfologias jellyfish em colisões de aglomerados de galáxias em geral.

This thesis is concerned with the targeting of emission line galaxies with FMOS (Fibre Multi-Object Spectrograph) to determine properties of star forming galaxies at redshift ~1.5, and provide measurements of the growth rate of large-scale structure through Redshift Space Distortions (RSDs). I also consider the opportunities of targeting the passive galaxy population at high redshift, through measurements of their continuum. I start with the extensive broad-band photometric data available in the UKIDSS-UDS (United Kingdom Infrared Telescope Deep Sky Survey - Ultra-Deep Survey) field which is used to produce a band-merged catalogue, later used for determining photometric redshifts. In producing this catalogue, I approach the issue of source confusion present in the deep Spitzer imaging using z-band priors on profile position and shape and an iterative Expectation-Maximisation algorithm. Photometric redshift estimates are compared against colour selections as potential targeting techniques for a wide-area redshift survey with FMOS. Different photometry survey areas are considered, and the quality of selection given the available broad-band data tested, by adjusting the photometric catalogue produced for the UDS. The results indicate that the SWIRE (Spitzer Wide area InfraRed Extragalactic Survey) fields are too small to provide adequate sources with a consistent selection mechanism. The CFHTLS (Canada-Frace-Hawaii Telescope Legacy Survey) would have a large enough area given deeper z'-band imaging, and SWIRE-depth coverage in the Spitzer 3.6μm and 4.5μm bands. I present FMOS commissioning data obtained for the UDS field, including the spectroscopic targeting of sources form the High-Z Emission Line Survey (HiZELS). With this data, I am able to test the current quality of flux calibration using cool stars targeted simultaneously and the level of systematic errors left by sky-subtraction. The sample of HiZELS sources selected to place Hα at z~1.45 show low contamination from other emission lines, and only one out of 9 targets assigned a redshift has any indication of AGN activity. Finally, I present longslit observations of faint, passive galaxies at redshift z~1.9, selected as members of a possible cluster, JKCS 041, selected from broad band colours. One object was observed with high enough signal to noise to constrain the position of the 4000 Å / Balmer break, providing a tighter constraint on the photometric redshift of 1.8867 ^+0.0034 -0.0117.

Cette thèse présente un certain nombre de résultats récents à propos de l'évolution des galaxies et la cosmologie, à partir de l'observation d'amas de galaxies en lumière visible. Nous introduisons d'abord les principales propriétés des amas de galaxies (Chapitre 1.1) et la façon dont ces objets permettent de contraindre le modèle cosmologique standard (Chapitre 1.2). Une grande partie des résultats présentés ici ont été obtenus à partir de l'étude du relevé d'amas DAFT/FADA, qui regroupe des amas dans la gamme de décalages spectraux 0.4<br>This thesis presents some recent results concerning galaxy evolution and cosmology,based on the observation of galaxy clusters at optical wavelengths. We first introduce the main properties of galaxy clusters (Sect. 1.1) and how they can be used for cosmology within the standard cosmological model (Sect. 1.2). A large fraction of the presented results comes from the study of the DAFT/FADA galaxy cluster survey at redshifts 0.4 &lt; z &lt; 0.9 (Sect. 1.3). We divide our study in two parts according to the observable that is considered: galaxy luminosity or galaxy shape. The distribution of galaxy luminosities is called the galaxy luminosity function (GLF), which can be used to probe the evolution of cluster galaxies (Sect. 2.1). Computing the GLFs for a sub sample of 25 DAFT/FADA clusters, we find that faint blue star forming galaxies are quenched into red quiescent galaxies from high redshift until today. Comparing to the field shows that this transformation is more efficient in high density environments.We also study the fraction of baryons in galaxy groups and clusters (Sect. 2.2). Wefind that in groups, the stars contained in galaxies can reach masses of the same order as those of the intra-cluster gas, while in clusters they are usually negligible relatively to the gas. Taking both stars and gas into account we constrain the matter density parameter Galaxy shapes are distorted by foreground objects that bend light in their vicinity. This lensing signal can be exploited to measure the mass distribution of a foreground cluster. We review the basic theory of weak lensing and shear measurement (Sect. 3.1), and then apply it to a subsample of 16 DAFT/FADA clusters, with Subaru/SuprimeCam or CFHT/MegaCam imaging (Sect. 3.2). We estimate the masses of these clusters, and take advantage of the large fields of view of our images to detect filaments and structures in the cluster vicinity, observationally supporting the hierarchical scenario of cluster growth. Finally, we detect shear peaks in Euclid-like simulations, and use their statistics as a cosmological probe, similarly to cluster counts (Sect. 3.3). We forecast the cosmological constraints that this technique will achieve when applied to the Euclid space mission, and develop a tomographic analysis that adds information from redshifts. We conclude with a discussion of our perspectives on future studies in all the fieldsinvestigated in the present thesis

Using new wide-area galaxy redshift surveys, we explore the evolutionof the most massive galaxies and the most luminous quasars in the universe over much of cosmic history. Quasars and massive red galaxies both areextremes; the most luminous high redshift quasars likely play a key role in shaping their nearby environment and the universe as a whole. The mostmassive galaxies represent the end points of galaxy evolution and containa fossil record of the galaxy evolution process.Using the AGES redshift survey completed with the MMT and the Hectospecmulti-object spectrograph as well as new $z$-band observations of the NOAO Deep Wide-Field Survey Bootes field, we report the discovery of threenew quasars at z>5. We explore new mid-infrared selection in light of thesethree new quasars and place constraints on the slope of the high-redshiftquasar luminosity function.At lower redshift (0.1<z<0.4) we measure the scatter in red galaxy colorsaround the optical red-sequence using imaging and spectroscopy from theSloan Digital Sky Survey. With our sample of nearly 20,000 massiveearly-type galaxies (L>2.2L*), we find that the scatter around the color-magnitude relation is quite small in colors studied.Each of three model star formation histories can reproduce the scatter we measure, none of the models producecolor distributions matching those observed.We measure the evolution of the LRG luminosity function in the redshift range 0.1<z<0.9. We find that theLRG population has evolved little beyond the passive fading of its stellar populations since z~0.9. The most massive (L>3L*)red galaxies have grown by less than 50% (at 99% confidence) since z=0.9 in stark contrast to the factor of 2 to 4 growth observed in the L* red galaxy population over the same epoch.Finally, we introduce the PRIsm MUlti-object Survey (PRIMUS), a new redshiftsurvey aimed at collecting ~300,000 galaxy spectra over 10 sq. deg toz~1. We summarize the current status of PRIMUS observations and datareductions and present several survey statistics. PRIMUS is the largestexisting redshift survey at intermediate redshift and holds the largestsample of redshifts for Spitzer and X-ray detected objects.

The formation of stars from interstellar gas is the cornerstone of galaxy evolution. This thesis represents work undertaken in order to characterise the role of cool interstellar gas, and its relation to star formation, in galaxy evolution across cosmic time. In particular, it concentrates on star forming galaxies at the extremes of the galaxy assembly spectrum - extremely faint dwarfs, and extremely luminous starbursts - in an attempt to test the limits of galaxy evolution models. The thesis falls into two complimentary halves, addressing topics in the low redshift and high redshift Universe respectively. In the low redshift Universe, I discuss multi-wavelength studies of large samples of z rv O galaxies, which include extremely faint dwarf galaxies in the Local Volume. Using these samples, it is possible to derive a multitude of physical parameters (including star formation rates, stellar masses, and gas masses) which allow the interrelationship between star formation and gas content to be assessed in a statistically significant manner. In particular, modern wide field surveys (combined with deep, volume-limited data) allow trends to be analysed across many orders of magnitude in galaxy mass and star formation rate, shedding light on the global properties of galaxies in the local Universe. Moving to higher redshift, I discuss targeted observations of molecular gas in extreme star forming galaxies in the early Universe. These 'sub-millimetre' galaxies number amongst the most luminous objects ever discovered, and molecular gas observations have the power to uncover many of their physical properties, including their morphologies, kinematics, and star formation behaviour. I begin by presenting high-resolution observations of a small number of these galaxies at z rv 2, and discussing the implications for galaxy evolution studies. The final chapter of this thesis consists of the results of a survey for molecular gas in sub-millimetre galaxies conducted over the last decade, which represents the largest single study of molecular gas in the early Universe to date.

Despite considerable progress in recent years, a complete description of the physical drivers of galaxy formation and evolution remains elusive, in part because of our poor understanding of star formation, and how star formation in galaxies is regulated by feedback from supernovae and massive stellar winds. Insight into the star formation histories of galaxies, and the interplay between star formation and feedback, can be gained by measuring their chemical abundances, which until recently has only been possible for galaxies in the nearby universe. However, reliable star formation and abundance calibrations have been hampered by various systematic uncertainties, and the lack of a suitable spectrophotometric sample with which to develop better calibrations. To address the limitations of existing surveys, we have obtained integrated optical spectra for a diverse sample of more than four hundred nearby star-forming galaxies. Using these data, in conjunction with observations from the Sloan Digital Sky Survey, we conduct a detailed analysis of optical star formation indicators, and develop empirical calibrations for the [O II] 3727 and H-beta 4861 nebular emission lines. Next, we investigate whether integrated spectroscopy of star forming galaxies can be used to infer their gas-phase oxygen abundances in the presence of radial abundance gradients, diffuse-ionized gas emission, and dust attenuation. We conclude that the integrated R23 parameter is generally insensitive to these systematic effects, enabling the gas-phase metallicity to be measured with a precision of +/-0.1 dex. We apply these methods to study the evolution in the luminosity-metallicity relation at 0<z<1 based on an analysis of more than 3500 I-band selected galaxies observed as part of the AGN and Galaxy Evolution Survey, and data culled from the literature. Our principal results are that, at fixed luminosity, the mean gas-phase metallicity of luminous (MB<-19 mag), star-forming galaxies at z=1 is a factor of two lower than the gas-phase metallicity in comparably luminous galaxies at z=0. However, after accounting for the effects of luminosity evolution, we find that the amount of chemical evolution for luminous galaxies corresponds to an increase of only 10%-20% since z1⁺ё, assuming a direct evolutionary connection between nearby and distant star-forming galaxies.

This thesis presents the first detailed analysis of three extragalactic fields observed by the infrared satellite, AKARI. AKARI is the only telescope able to observe deeply in the Spitzer/IRAC - Spitzer/MIPS band gap of 8-24 microns. The first analysis of these extragalactic fields, was to perform galaxy number counts, the most basic statistical property of galaxy populations. Presented are the counts at 3, 4, 7, 11, 15 and 18 microns. These number counts were compared with published results and galaxy evolution models. These models are dependent on both the Spectral Energy Distribution (SED) templates and evolution of the galaxy types. The phenomenological backwards evolution model of Pearson 2005 appeared to be consistent with the number counts. To probe this, number counts were extracted from below the survey limit by performing Probability of Deflection (P(D)) fluctuation analysis. The Pearson model was found to be consistent with the 11 microns P(D) analysis but not with the 15 microns. The results from the 15 microns P(D) analysis indicates that the Pearson model under predicts the evolution of star forming galaxies. Multi-wavelength band-merged catalogues for the two deep extragalactic fields were created using AKARI data from the work of this thesis and ancillary data. The separation of galaxy type using AKARI/IRC filter colours was explored. For z < 2 a separation criteria was found for Active Galactic Nuclei (AGN), but to accurately classify galaxy type, SED fitting is required. Submm-selected galaxies detected by AKARI were found to resemble scaled-up normal local spiral galaxies, rather than starbursts, consistent with them lying on the high-redshift `main sequence' unlike local ultraluminous infrared galaxies. The thesis concludes by measuring the percentage of the far-infrared Cosmic Infrared Background (CIB) resolved by AKARI mid-infrared galaxies. By performing stacking analysis on a Herschel/SPIRE 250 microns image of AKARI galaxy positions, it was found that AKARI mid-infrared galaxies resolve ~10% of the 250 micron CIB.

Following a review of the basic ingredients necessary for constructing models of galactic chemical evolution, with a special emphasis on the issue of stellar evolution and nucleosynthesis (which is treated in detail in Chapter 2), I continue with the basic equations that one needs to solve in order to follow the chemical evolution of a system of gas and stars in time and space. The assumptions of the models I have handled with the aim of addressing different aspects of the formation and evolution of the Milky Way and elliptical galaxies are discussed in Chapter 3. In Chapters 4 and 5, I present the results of my own research, mainly focusing on how important is the analysis of the chemical abundances and especially abundance ratios in galaxies for understanding their formation and evolution, in spite of the many parameters involved in the modelling.

Magister Scientiae - MSc (Physics)<br>Studying clustering on small scales (<10Mpc) over a large span of red- shifts allows us to connect galaxies to underlying cosmic large-scale structure, and thereby provide constraints on the physical processes that drive galaxy evolution. Relatedly, studying the relative bias of galaxies and their halo occupancy quanti es how the underlying dark matter distribution is traced by baryons in galaxies. Comparing model predictions to current and future multi-wavelength galaxy surveys, en- ables a greater understanding of how galaxy formation processes impact the relationship between galaxies and dark matter

This thesis describes a large-area 2μm survey undertaken on the U.K. Infrared Telescope in Hawaii, using a new infrared imaging camera. The survey convers 594 hskip 0.4cm and is complete and uniform to a limit of K = 17. The main aim of the survey was to construct a sample of galaxies, selected by their 2μm flux, for studies of galaxy evolution. The subsidiary aim was to survey the 2μm Universe and search for any new populations of infrared objects, such as protogalaxies and brown dwarf stars. The first half of this thesis is concerned with the analysis of astronomical data. The detailed methods for constructing the infrared survey are described, including flatfielding, astrometry, mosaicing and photometry. Also described are optical CCD observations which cover the survey area to provide optical-infrared colours of almost all the objects in the sample. The methods of reducing, calibrating and matching the CCD data with the infrared data are detailed. For the study of galaxy evolution the redshifts of 53 K band selected galaxies, with a well defined completeness, were measured using multiple object spectrographs. The reduction of the spectra and the methods used for securing the redshifts, including the cross-correlation technique, are described. The second half of this thesis is about the scientific results from this survey. Firstly, it appears that no new large populations of objects appear, in particular there appear to be no objects <i>only</i> detected in K. A few extremely red objects are found, however their true nature is unclear in the absence of spectra. The best evidence is that a few of them are very cool stars. Secondly, the galaxy population appears to have very red R-K colours, although not necessarily so red in B-K, and the K band number-magnitude counts exhibit a much smaller excess over the no-evolution prediction than do the B band optical counts. The K band counts are consistent with only a small amount of luminosity evolution.