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Dissertations / Theses on the topic 'Galaxy: general'

Author: Grafiati

Published: 4 June 2021

Last updated: 26 July 2025

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1

Rosselli, Damiano. "Probing general relativity: new measures of gravitational redshifts in galaxy clusters." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25349/.

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In this Thesis work we test the Einstein theory of General Relativity by measuring the gravitational redshift effect in galaxy clusters, within the ΛCDM cosmological framework. To perform the gravitational redshift measurements, we create two new cluster member galaxies by exploiting the galaxy coordinates and spectroscopic redshifts derived from the sixteenth data release of the Sloan Digital Sky Survey, and two cluster catalogs, namely the Wen-Han-Liu cluster catalog (WHL15) and the cluster catalog derived from the latest data release of the Dark Energy Survey Instrument (DESI). We accura

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2

Hood, Ross John. "Characterising the optical properties of galaxy clusters with GMPhoRCC." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9638.

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The properties of galaxy clusters, such as abundance and mass to light ratios, have long been used to investigate and constrain cosmology. With vast numbers of newly detected clusters, such as from the Planck mission (Planck Collaboration et al., 2013), full determination of cluster properties, particularly mass, can be hugely expensive and time consuming. Optical characterisation o ers a cheap solution, using optical data alone to estimate cluster properties such as redshift. With the abundance of current optical data, such as from the Sloan Digital Sky Survey (SDSS), (Ahn et al., 2012) and u

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3

Rykoff, E. S., E. Rozo, D. Hollowood, et al. "THE REDMAPPER GALAXY CLUSTER CATALOG FROM DES SCIENCE VERIFICATION DATA." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621223.

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We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large photometric surveys. The updated algorithm is applied to 150 deg(2) of Science Verification (SV) data from the Dark Energy Survey (DES), and to the Sloan Digital Sky Survey (SDSS) DR8 photometric data set. The DES SV catalog is locally volume limited and contains 786 clusters with richness lambda > 20 (roughly equivalent to M500c greater than or similar to 10(14) h(70)(-1)M(circle dot)) and 0.2 < z < 0.9. The DR8 catalog consists of 26,311 clusters with 0.08 < z < 0.6, with

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Baxter, Eric, Chihway Chang, Bhuvnesh Jain, et al. "The Halo Boundary of Galaxy Clusters in the SDSS." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624484.

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Analytical models and simulations predict a rapid decline in the halo density profile associated with the transition from the "infalling" regime outside the halo to the "collapsed" regime within the halo. Using data from SDSS, we explore evidence for such a feature in the density profiles of galaxy clusters using several different approaches. We first estimate the steepening of the outer galaxy density profile around clusters, finding evidence for truncation of the halo profile. Next, we measure the galaxy density profile around clusters using two sets of galaxies selected on color. We find ev

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5

Farahi, Arya, August E. Evrard, Eduardo Rozo, Eli S. Rykoff, and Risa H. Wechsler. "Galaxy cluster mass estimation from stacked spectroscopic analysis." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621426.

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We use simulated galaxy surveys to study: (i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and (ii) the accuracy of a mean dynamical cluster mass, M-sigma(lambda), derived from stacked pairwise spectroscopy of clusters with richness lambda. Using similar to 130 000 galaxy pairs patterned after the Sloan Digital Sky Survey (SDSS) redMaPPer cluster sample study of Rozo et al., we show that the pairwise velocity probability density function of central-satellite pairs with m(i) < 19 in the simulation matches the form seen in Rozo et al. Through joint membersh

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6

Zasowski, G., R. E. Cohen, S. D. Chojnowski, et al. "Target Selection for the SDSS-IV APOGEE-2 Survey." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626051.

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APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing similar to 3. x. 10(5) stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding on APOGEE's goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch and red clump stars, RR Lyrae, lowmass dwarf stars, young stellar objects, and

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7

Frusciante, Noemi. "Deviations from General Relativity in Cosmology and Astrophysics." Doctoral thesis, SISSA, 2014. http://hdl.handle.net/20.500.11767/3861.

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Two of the most prominent challenges of Modern Cosmology are the recent late-time accelerated expansion of the Universe and Dark Matter (DM). DM is of fundamental importance in the process of structure formation at galactic, extragalactic and cosmic scales. It seems to dominate down to small galactocentric radii, as highlighted by the galaxies rotation curves and on cosmic scale, it is well known that the spatial distribution of galaxies is biased with respect to the underlying DM distribution. This relation is called ``bias''. Part of this thesis is devoted to the investigation of the

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8

Rees, Bryan. "A study of planetary nebulae in and towards the Galactic Bulge." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/a-study-of-planetary-nebulae-in-and-towards-the-galactic-bulge(ff6c0373-e5a5-491f-b5fb-bda36acac8ba).html.

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A planetary nebula (PN) consists of material, mainly gas, that has been ejected from a star on the asymptotic giant branch of its life cycle. This material emits electromagnetic radiation due to photoionization and recombination, collisional and radiative excitation or free-free radiation. The envelope of material moves outwards from the central star and may take one of a variety of shapes. These shapes are believed to be sculpted by the stellar wind, magnetic fields and interactions with a binary companion. However, within a time scale of as little as 10 000 years the nebula fades from view a

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9

Hennig, C., J. J. Mohr, A. Zenteno, et al. "Galaxy Populations in Massive Galaxy Clusters to z = 1.1: Color Distribution, Concentration, Halo Occupation Number and Red Sequence Fraction." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623801.

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We study the galaxy populations in 74 Sunyaev-Zeldovich effect selected clusters from the South Pole Telescope survey, which have been imaged in the science verification phase of the Dark Energy Survey. The sample extends up to z similar to 1.1 with 4 x 10(14)M(circle dot) <= M-200 <= 3 x 10(15)M(circle dot). Using the band containing the 4000 angstrom break and its redward neighbour, we study the colour-magnitude distributions of cluster galaxies to similar to m(*) + 2, finding that: (1) The intrinsic rest frame g - r colour width of the red sequence (RS) population is similar to 0.03 out to

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10

Dawson, William Anthony. "Constraining Dark Matter Through the Study of Merging Galaxy Clusters." Thesis, University of California, Davis, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3602041.

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<p> <b>Context:</b> The majority (~85%) of the matter in the universe is composed of dark matter, a mysterious particle that does not interact via the electromagnetic force yet does interact with all other matter via the gravitational force. Many direct detection experiments have been devoted to finding interactions of dark matter with baryonic matter via the weak force. It is still possible that dark matter interacts with itself via a strong scale force and has a self-scattering cross-section of ~0.5 cm<sup>2</sup>g<sup> -1</sup>. In fact such a strong scale scattering force could resolve s

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11

Cibirka, N., E. S. Cypriano, F. Brimioulle, et al. "CODEX weak lensing: concentration of galaxy clusters at z ∼ 0.5." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623800.

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We present a stacked weak-lensing analysis of 27 richness selected galaxy clusters at 0.40 <= z <= 0.62 in the COnstrain Dark Energy with X-ray galaxy clusters (CODEX) survey. The fields were observed in five bands with the Canada-France-Hawaii Telescope (CFHT). We measure the stacked surface mass density profile with a 14 sigma significance in the radial range 0.1 < R Mpc h(-1) < 2.5. The profile is well described by the halo model, with the main halo term following a Navarro-Frenk-White profile (NFW) profile and including the off-centring effect. We select the background sample using a conse

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Schiavon, Ricardo P., Olga Zamora, Ricardo Carrera, et al. "Chemical tagging with APOGEE: discovery of a large population of N-rich stars in the inner Galaxy." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623045.

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Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general is an important unsolved problem in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE (Apache Point Observatory Galactic Evolution Experiment) of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anticorr

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Drake, A. J., S. G. Djorgovski, M. Catelan, et al. "The Catalina Surveys Southern periodic variable star catalogue." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625504.

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Here, we present the results from our analysis of 6 yr of optical photometry taken by the Siding Spring Survey (SSS). This completes a search for periodic variable stars within the 30 000 deg(2) of the sky covered by the Catalina Surveys. The current analysis covers 81 million sources with declinations between -20 degrees. and -75 degrees. with median magnitudes in the range 11 < V < 19.5. We find approximately 34 000 new periodic variable stars in addition to the similar to 9000 RR Lyrae that we previously discovered in SSS data. This brings the total number of periodic variables identified i

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Dexter, J., A. Deller, G. C. Bower, et al. "Locating the intense interstellar scattering towards the inner Galaxy." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625730.

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We use VLBA+VLA observations to measure the sizes of the scatter-broadened images of six of the most heavily scattered known pulsars: three within the Galactic Centre (GC) and three elsewhere in the inner Galactic plane (Delta l < 20 degrees). By combining the measured sizes with temporal pulse broadening data from the literature and using the thin-screen approximation, we locate the scattering medium along the line of sight to these six pulsars. At least two scattering screens are needed to explain the observations of the GC sample. We show that the screen inferred by previous observations of

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15

Haan, T. de, B. A. Benson, L. E. Bleem, et al. "COSMOLOGICAL CONSTRAINTS FROM GALAXY CLUSTERS IN THE 2500 SQUARE-DEGREE SPT-SZ SURVEY." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622452.

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We present cosmological parameter constraints obtained from galaxy clusters identified by their SunyaevZel'dovich effect signature in the 2500 square-degree South Pole Telescope Sunyaev Zel'dovich (SPT-SZ) survey. We consider the 377 cluster candidates identified at z > 0.25 with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data

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Rozo, E., and T. Abbott. "The Dark Energy Survey: more than dark energy – an overview." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621432.

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This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and othe

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Monna, A., S. Seitz, I. Balestra, et al. "Precise strong lensing mass profile of the CLASH galaxy cluster MACS 2129." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/624505.

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We present a detailed strong lensing (SL) mass reconstruction of the core of the galaxy cluster MACS J2129.4-0741 (z(cl) = 0.589) obtained by combining high-resolution Hubble Space Telescope photometry from the CLASH (Cluster Lensing And Supernovae survey with Hubble) survey with new spectroscopic observations from the CLASH-VLT (Very Large Telescope) survey. A background bright red passive galaxy at z(sp) = 1.36, sextuply lensed in the cluster core, has four radial lensed images located over the three central cluster members. Further 19 background lensed galaxies are spectroscopically confirm

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18

Blanton, Michael R., Matthew A. Bershady, Bela Abolfathi, et al. "Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624901.

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We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas d

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Leaf, Kyle, and Fulvio Melia. "A two-point diagnostic for the H ii galaxy Hubble diagram." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/627132.

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A previous analysis of starburst-dominated HII galaxies and HII regions has demonstrated a statistically significant preference for the Friedmann-Robertson-Walker cosmology with zero active mass, known as the R-h = c(t) universe, over Lambda cold dark matter (Lambda CDM) and its related dark-matter parametrizations. In this paper, we employ a two-point diagnostic with these data to present a complementary statistical comparison of Rh = ct with Planck Lambda CDM. Our two-point diagnostic compares, in a pairwise fashion, the difference between the distance modulus measured at two redshifts with

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Zaritsky, Dennis, Denija Crnojević, and David J. Sand. "ARE SOME MILKY WAY GLOBULAR CLUSTERS HOSTED BY UNDISCOVERED GALAXIES?" IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621403.

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The confirmation of a globular cluster (GC) in the recently discovered ultrafaint galaxy Eridanus II (Eri II) motivated us to examine the question posed in the title. After estimating the halo mass of Eri II using a published stellar mass-halo mass relation, the one GC in this galaxy supports extending the relationship between the number of GCs hosted by a galaxy and the galaxy's total mass about two orders of magnitude in stellar mass below the previous limit. For this empirically determined specific frequency of between 0.06 and 0.39 GCs per 10(9)M(circle dot) of total mass, the surviving Mi

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Mulroy, Sarah L., Sean L. McGee, Steven Gillman, et al. "Galaxy cluster luminosities and colours, and their dependence on cluster mass and merger state." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625963.

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We study a sample of 19 galaxy clusters in the redshift range 0.15 < z < 0.30 with highly complete spectroscopic membership catalogues (to K < K*(z) + 1.5) from the Arizona Cluster Redshift Survey, individual weak-lensing masses and near-infrared data from the Local Cluster Substructure Survey, and optical photometry from the Sloan Digital Sky Survey. We fit the scaling relations between total cluster luminosity in each of six bandpasses (grizJK) and cluster mass, finding cluster luminosity to be a promising mass proxy with low intrinsic scatter sigma ln (L|M) of only similar to 10-20 per cent

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Huang, Hung-Jin, Rachel Mandelbaum, Peter E. Freeman, et al. "Intrinsic alignments in redMaPPer clusters – I. Central galaxy alignments and angular segregation of satellites." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622108.

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The shapes of cluster central galaxies are not randomly oriented, but rather exhibit coherent alignments with the shapes of their parent clusters as well as with the surrounding large-scale structures. In this work, we aim to identify the galaxy and cluster quantities that most strongly predict the central galaxy alignment phenomenon among a large parameter space with a sample of 8237 clusters and 94 817 members within 0.1 < z < 0.35, based on the red-sequence Matched-filter Probabilistic Percolation cluster catalogue constructed from the Sloan Digital Sky Survey. We first quantify the alignme

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Melchior, P., D. Gruen, T. McClintock, et al. "Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification data." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625502.

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We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 <= lambda <= 180 and redshift 0.2 <= z <= 0.8, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentring; deviations from the NFW halo pro

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Zucker, Catherine, Lisa May Walker, Kelsey Johnson, Sarah Gallagher, Katherine Alatalo, and Panayiotis Tzanavaris. "HIERARCHICAL FORMATION IN ACTION: CHARACTERIZING ACCELERATED GALAXY EVOLUTION IN COMPACT GROUPS USING WHOLE-SKY WISE DATA." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621221.

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Compact groups provide an environment to study the growth of galaxies amid multiple prolonged interactions. With their dense galaxy concentrations and relatively low velocity dispersions, compact groups mimic the conditions of hierarchical galaxy assembly. Compact group galaxies are known to show a bimodality in Spitzer IRAC infrared color space: galaxies are preferentially either quiescent with low specific star formation rates (SSFRs) or prolifically forming stars-galaxies with moderate levels of specific star formation are rare. Previous Spitzer IRAC studies identifying this "canyon" have b

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Tucker, Evan, Matthew G. Walker, Mario Mateo, et al. "Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625748.

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We report the results of a pilot program to use the Magellan/M2FS spectrograph to survey the galactic populations and internal kinematics of galaxy clusters. For this initial study, we present spectroscopic measurements for 223 quiescent galaxies observed along the line of sight of the galaxy cluster Abell 267 (z similar to 0.23). We develop a Bayesian method for modeling the integrated light from each galaxy as a simple stellar population, with free parameters that specify the redshift (v(los)/c) and characteristic age, metallicity ([Fe/H]), alpha-abundance ([alpha/Fe]), and internal velocity

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Souza, Juliana Crestani Ribeiro de. "Spatial distribution of galactic globular clusters : distance uncertainties and dynamical effects." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/156776.

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Fornecemos uma amostra de 170 Aglomerados Globulares Galácticos (GCs) e analisamos as propriedades de sua distribuição espacial. Utilizando um vasto catálogo de nuvens escuras identificadas, listamos os GCs que estão atrás de uma ou mais delas e que podem estar submetidos a uma extinção mais complexa do que a considerada por mapas de extinção. Valores de incerteza em distância são obtidos da literatura recente e comparados com valores derivados de uma fórmula de propagação de erro. GCs são agrupados de acordo com características inusitadas, tais como idades relativamente jovens ou possível con

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More, Surhud, Hironao Miyatake, Masahiro Takada, et al. "DETECTION OF THE SPLASHBACK RADIUS AND HALO ASSEMBLY BIAS OF MASSIVE GALAXY CLUSTERS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621397.

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We show that the projected number density profiles of Sloan Digital Sky Survey photometric galaxies around galaxy clusters display strong evidence for the splashback radius, a sharp halo edge corresponding to the location of the first orbital apocenter of satellite galaxies after their infall. We split the clusters into two subsamples with different mean projected radial distances of their members, < R-mem >, at fixed richness and redshift. The sample with smaller < R-mem > has a smaller ratio of the splashback radius to the traditional halo boundary R-200m than the subsample with larger < R-m

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Bayliss, M. B., J. Ruel, C. W. Stubbs, et al. "SPT-GMOS: A GEMINI/GMOS-SOUTH SPECTROSCOPIC SURVEY OF GALAXY CLUSTERS IN THE SPT-SZ SURVEY." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622337.

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We present the results of SPT-GMOS, a spectroscopic survey with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South. The targets of SPT-GMOS are galaxy clusters identified in the SPT-SZ survey, a millimeter-wave survey of 2500 deg(2) of the southern sky using the South Pole Telescope (SPT). Multi-object spectroscopic observations of 62 SPT-selected galaxy clusters were performed between 2011 January and 2015 December, yielding spectra with radial velocity measurements for 2595 sources. We identify 2243 of these sources as galaxies, and 352 as stars. Of the galaxies, we identify 1579 as

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Jencson, Jacob E., Mansi M. Kasliwal, Joel Johansson, et al. "SPIRITS 15c and SPIRITS 14buu: Two Obscured Supernovae in the Nearby Star-forming Galaxy IC 2163." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623863.

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SPitzer InfraRed Intensive Transients Survey-SPIRITS-is an ongoing survey of nearby galaxies searching for infrared (IR) transients with Spitzer/IRAC. We present the discovery and follow-up observations of one of our most luminous (M-[4.5] = -17.1 +/- 0.4 mag, Vega) and reddest ([3.6] - [4.5] = 3.0 +/- 0.2 mag) transients, SPIRITS 15c. The transient was detected in a dusty spiral arm of IC. 2163 (D approximate to 35.5 Mpc). Pre-discovery ground-based imaging revealed an associated, shorter-duration transient in the optical and near-IR (NIR). NIR spectroscopy showed a broad (approximate to 8400

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Wei, Jun-Jie, Xue-Feng Wu, and Fulvio Melia. "The H II galaxy Hubble diagram strongly favours R-h = ct over Lambda CDM." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622740.

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We continue to build support for the proposal to use H II galaxies (HIIGx) and giant extragalactic H II regions (GEHR) as standard candles to construct the Hubble diagram at redshifts beyond the current reach of Type Ia supernovae. Using a sample of 25 high-redshift HIIGx, 107 local HIIGx, and 24 GEHR, we confirm that the correlation between the emission -line luminosity and ionized -gas velocity dispersion is a viable luminosity indicator, and use it to test and compare the standard model Lambda CDM and the R-h = ct universe by optimizing the parameters in each cosmology using a maximization

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Fernández-Trincado, J. G., O. Zamora, D. A. García-Hernández, et al. "Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625816.

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We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe]. < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] greater than or similar to-1.0) sample stars, which is at odds

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Johannsen, Tim. "Testing General Relativity in the Strong-Field Regime with Observations of Black Holes in the Electromagnetic Spectrum." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/238893.

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General relativity has been tested by many experiments, which, however, almost exclusively probe weak spacetime curvatures. In this thesis, I create two frameworks for testing general relativity in the strong-field regime with observations of black holes in the electromagnetic spectrum using current or near-future instruments. In the first part, I design tests of the no-hair theorem, which uniquely characterizes the nature of black holes in terms of their masses and spins in general relativity and which states that these compact objects are described by the Kerr metric. I investigate a quasi-K

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Palmese, A., O. Lahav, M. Banerji, et al. "Comparing Dark Energy Survey and HST–CLASH observations of the galaxy cluster RXC J2248.7−4431: implications for stellar mass versus dark matter." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622739.

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We derive the stellar mass fraction in the galaxy cluster RXC J2248.7-4431 observed with the Dark Energy Survey (DES) during the Science Verification period. We compare the stellar mass results from DES (five filters) with those from the Hubble Space Telescope Cluster Lensing And Supernova Survey (CLASH; 17 filters). When the cluster spectroscopic redshift is assumed, we show that stellar masses from DES can be estimated within 25 per cent of CLASH values. We compute the stellar mass contribution coming from red and blue galaxies, and study the relation between stellar mass and the underlying

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Yukita, M., A. Ptak, A. E. Hornschemeier, et al. "Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623858.

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We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Cha

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Weisz, Daniel R., Sergey E. Koposov, Andrew E. Dolphin, et al. "A HUBBLE SPACE TELESCOPE STUDY OF THE ENIGMATIC MILKY WAY HALO GLOBULAR CLUSTER CRATER." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621220.

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We analyze the resolved stellar populations of the faint stellar system, Crater, based on deep optical imaging taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Crater's color-magnitude diagram (CMD) extends similar to 4 mag below the oldest main-sequence (MS) turnoff. Structurally, we find that Crater has a half-light radius of similar to 20 pc and no evidence for tidal distortions. We model. Crater's CMD as a simple stellar population (SSP) and alternatively by solving for its full star formation history. In both cases, Crater is well. described by an SSP with an age

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Kim, Junhan, Daniel P. Marrone, Chi-Kwan Chan, Lia Medeiros, Feryal Özel, and Dimitrios Psaltis. "BAYESIAN TECHNIQUES FOR COMPARING TIME-DEPENDENT GRMHD SIMULATIONS TO VARIABLE EVENT HORIZON TELESCOPE OBSERVATIONS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622523.

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The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius. A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to

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Balestra, I., A. Mercurio, B. Sartoris, et al. "CLASH-VLT: DISSECTING THE FRONTIER FIELDS GALAXY CLUSTER MACS J0416.1-2403 WITH ∼800 SPECTRA OF MEMBER GALAXIES." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621406.

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We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields cluster MACS. J0416.1-2403 (z = 0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over similar to 600 arcmin(2), including similar to 800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to similar to 2.2 r(200) (similar to 4Mpc). Our analysis of substructures reveals a complex system composed of a main massive clust

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Alberts, Stacey, Alexandra Pope, Mark Brodwin, et al. "STAR FORMATION AND AGN ACTIVITY IN GALAXY CLUSTERS FROM z = 1–2: A MULTI-WAVELENGTH ANALYSIS FEATURING HERSCHEL /PACS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621395.

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We present a detailed, multi-wavelength study of star formation (SF) and active galactic nucleus (AGN) activity in 11 near-infrared (IR) selected, spectroscopically confirmed massive (greater than or similar to 10(14)M(circle dot)) galaxy clusters at 1 < z < 1.75. Using new deep Herschel/PACS imaging, we characterize the optical to far-IR spectral energy distributions (SEDs) for IR-luminous cluster galaxies, finding that they can, on average, be well described by field galaxy templates. Identification and decomposition of AGNs through SED fittings allows us to include the contribution to clust

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Dias, Bruno Moreira de Souza. "Formation and evolution of globular clusters in the Galaxy and Magellanic Clouds." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-26082014-090039/.

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Globular clusters are tracers of the formation and evolution of their host galaxies. Kinematics, chemical abundances, age and position of the clusters allows tracing interactions between Milky Way and surrounding galaxies and outlines their chemical enrichment history. In this thesis we analyse mid-resolution spectra of about 800 red giant stars in 51 Galactic globular clusters. It is the first time that [Fe/H] and [Mg/Fe] derived in a consistent way are published for such a huge sample of globular clusters, almost 1/3 of the total number of catalogued clusters. Our metallicities are showed to

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Trusov, Svyatoslav. "Exploitation des données du DESI Bright Galaxy Survey pour contraindre la nature de l’énergie noire et la relativité générale." Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS296.

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DESI (Dark Energy Spectroscopic Instrument, i.e. l'Instrument Spectroscopique de l'Énergie Noire) est un instrument spectroscopique attaché à un téléscope de 4m à l'observatoire Kitt Peak aux États-Unis. En collectant les spectres de plus de 40 millions de galaxies, on peut calculer leur distance radiale et ainsi créer une carte tri-dimensionnelle des grandes structures de notre Univers. Puisque la gravité est la force dominante à ces échelles, en mesurant la vitesse à laquelle la matière s'agglomère pour former des structures comme les galaxies, on peut contraindre les théories de la gravité.

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Stevance, H. F., Richard Igance, P. A. Crowther, J. R. Maund, B. Davies, and G. Rate. "Probing the Rotational Velocity of Galactic WO Stars with Spectropolarimetry." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/5506.

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Oxygen sequence Wolf-Rayet stars (WO) are thought to be the final evolution phase of some high-mass stars, as such they may be the progenitors of Type Ic SNe as well as potential progenitors of broad-lined Ic and long gamma-ray bursts. We present the first spectropolarimetric observations of the Galactic WO stars WR93b and WR102 obtained with FORS1 on the Very Large Telescope. We find no sign of a line effect, which could be expected if these stars were rapid rotators. We also place constraints on the amplitude of a potentially undetected line effect. This allows us to derive upper limits on t

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Pablo, Herbert, Noel Richardson, Anthony Moffat та ін. "A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Orionis Aa. III. Analysis of Optical Photometric (MOST) and Spectroscopic (Ground Based) Variations". Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/6234.

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We report on both high-precision photometry from the Microvariability and Oscillations of Stars (MOST) space telescope and ground-based spectroscopy of the triple system δ Ori A, consisting of a binary O9.5II+early-B(Aa1 and Aa2) with P=5.7 days, and a more distant tertiary(O9 IV P 400 years). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for three weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first time in non-phased data. From the spectroscopy, we have a well-constrained radial vel

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Klement, Robert, Anthony C. Carciofi, Thomas Rivinius, et al. "Revealing the Structure of the Outer Disks of Be Stars." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/2693.

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Context. The structure of the inner parts of Be star disks (≲ 20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on the other hand, are not observationally well-explored, as they are observable only at radio wavelengths. A steepening of the spectral slope somewhere between infrared and radio wavelengths was reported for several Be stars that were previously detected in the radio, but a convincing physical explanation for this trend has not yet been provided.

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Hubrig, S., K. Scholz, Wolf-Rainer Hamann, et al. "Searching for a Magnetic Field in Wolf-Rayet Stars Using FORS 2 Spectropolarimetry." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2694.

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To investigate if magnetic fields are present in Wolf–Rayet stars, we selected a few stars in the Galaxy and one in the Large Magellanic Cloud (LMC). We acquired low-resolution spectropolarimetric observations with the European Southern Observatory FORS 2 (FOcal Reducer low dispersion Spectrograph) instrument during two different observing runs. During the first run in visitor mode, we observed the LMC Wolf–Rayet star BAT99 7 and the stars WR 6, WR 7, WR 18, and WR 23 in our Galaxy. The second run in service mode was focused on monitoring the star WR 6. Linear polarization was recorded immedia

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Hosgor, Sumeyye. "Credit And Financing In Early Modern Ottoman Empire: The Galata Example." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614335/index.pdf.

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The present study aims to reveal the credit practice in Galata region in seventeenth century, through dealing with the credit relations between religious groups and the position of women in economic relations as the main themes. Galata was one of the most important international trade ports in seventeenth century for not only the Otoman Empire but also the Mediterranean region. While it was expected that the credit organization in Galata should be different than the ones of priorly studied cities of Anatoli, Kayseri and Bursa, as a result of the combination of multinational structure of the r

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Gozubuyuk, Melek Dilsad. "New Interpretations Of Domestic Space And Life: The Emergence Of Apartment Buildings In Nineteenth Century Istanbul." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605637/index.pdf.

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This thesis attempts to study the architectural and the social changes brought by the multi-story apartment buildings which emerged in the nineteenth century istanbul, in especially Galata-Pera region. A brief introduction to the modernization attempts of the Ottoman Empire, and also to the traditional dwellings and daily life of the Ottoman households before the nineteenth century constitute the first sections of the study. The architectural and the urban developments such as the new building regulations, architectural styles and building types as well as the social and cultural changes that

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TURRIZIANI, SARA. "Studying the spectral shape and the X-ray/UV: variability of active galactic nuclei with data from swift and XMM archives." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/202327.

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I Nuclei Galattici Attivi (AGN) hanno variazioni di flusso in tutte le bande dello spettro elettromagnetico. In effetti, la variabilità è stata una delle prime proprietà dei quasar ad essere riconosciuta. Sebbene la variabilità giochi un ruolo fondamentale nel dare una stima della grandezza del nucleo centrale degli AGN, la sua origine fisica rimane tuttora sconosciuta. Per spiegare le osservazioni ottiche spno stati proposti diversi meccanismi, ad esempio esplosioni di supernove, cattura di stelle, microlenti gravitazionali o instabilità del disco. La variabilità rapida nella banda X è dunque

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Lin, Pao-Chu, and 林寶珠. "Channel strategy of offshore fund agency business in Taiwan under the new “General Agent” system－a case study on Galaxy SICE." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/85281914448258673519.

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碩士<br>國立臺灣大學<br>財務金融學研究所<br>95<br>The research goal is to explore the changes of the channel strategy of the offshore fund agency business in Taiwan caused by the enforcement of the new General Agent system. The research selects Galaxy SICE as the sample company and uses SWOT model to observe and analyze the adjustment process of channel strategy of Galaxy SICE caused by the change of the industrial environment. The result of the research shows that the enforcement of the new “General Agent” system will decrease the bargaining power of the offshore funds agents in Taiwan, which leads to more s

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VIETRI, GIUSTINA. "The most luminous quasars of the universe: probing the AGN/galaxy co-evolution at its extremes." Doctoral thesis, 2018. http://hdl.handle.net/11573/1051847.

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The systematic, multi-frequency investigation of hyper-luminous quasars shining at the golden epoch of AGN activity offers the unique opportunity of studying the power and the effect of AGN feedback at its extreme. The WISE/SDSS- selected hyper-luminous quasar (WISSH) survey is an extensive multi-band observing program to investigate the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows. We found that WISSH AGN are typically powered by highly accreting (0.3-3 Ledd), ten billion solar masses SMBHs, demonstrating that WISSH provides a simple and valuable tool to

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De, los Ríos Martín Emilio. "Métodos de aprendizaje automático aplicados a problemas cosmológicos." Doctoral thesis, 2019. http://hdl.handle.net/11086/14284.

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Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2019.<br>En este trabajo presentaremos el estudio de diferentes problemas cosmológicos mediante la implementación de técnicas de aprendizaje automático. En la primera parte de la tesis se presenta el marco teórico necesario para estudiar los diferentes problemas cosmológicos que abordamos durante la tesis. Mientras que en el Capı́tulo 1 se presenta una introducción general sobre el modelo cosmológico estándar, en el Capı́tulo 2 se detallan los principales algoritmos de apren

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