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1
Combes, Francoise. "Galaxy Dynamics: Secular Evolution and Accretion." Proceedings of the International Astronomical Union 6, S271 (2010): 119–26. http://dx.doi.org/10.1017/s1743921311017522.
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AbstractRecent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation.
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Łokas, Ewa L. "An interesting case of the formation and evolution of a barred galaxy in the cosmological context." Astronomy & Astrophysics 642 (October 2020): L12. http://dx.doi.org/10.1051/0004-6361/202039425.
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Elongated, bar-like galaxies without a significant disk component, with little rotation support and no gas, often form as a result of tidal interactions with a galaxy cluster, as was recently demonstrated using the IllustrisTNG-100 simulation. Galaxies that exhibit similar properties are, however, also found to be infalling into the cluster for the first time. We use the same simulation to study in detail the history of such a galaxy over cosmic time in order to determine its origin. The bar appears to be triggered at t = 6.8 Gyr by the combined effect of the last significant merger with a subhalo and the first passage of another dwarf satellite, both ten times less massive than the galaxy. The satellites deposit all their gas in the galaxy, contributing to its third and last star-formation episode, which perturbs the disk and may also contribute to the formation of the bar. The galaxy then starts to lose its gas and dark matter due to its passage near a group of more massive galaxies. The strongest interaction involves a galaxy 22 times more massive, leaving the barred galaxy with no gas and half of its maximum dark matter mass. During this time, the bar grows steadily, seemingly unaffected by the interactions, although they may have aided its growth by stripping the gas. The studied galaxy, together with two other similar objects briefly discussed in this Letter, suggest the existence of a new class of early-type barred galaxies and thereby demonstrate the importance of interactions in galaxy formation and evolution.
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Combes, Françoise. "Ring and Lens Formation." International Astronomical Union Colloquium 157 (1996): 286–98. http://dx.doi.org/10.1017/s0252921100049927.
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AbstractThe dynamical mechanism to form rings at Lindblad resonances in a barred galaxy is now well-known: due to its dissipative character, the gas is forced in a spiral structure, and experiences torques from the bar potential. Angular momentum is transferred until gas accumulates in the resonant rings. Some problems remain however to account for all observations, such as the very different time-scales for nuclear, inner and outer ring formation, while the three are frequently observed in the same galaxy; the shapes, orientations and thickness of the rings, etc... The adequacy of the present gas dynamical modelizations is discussed.Lenses are secondary components of barred galaxies that could originate from bar evolution. No model until now has met the observational constraints, in particular the sharp edge of the lenses, their strong velocity anisotropy, and their small thickness. We propose here that lenses are the result of partial bar destruction, a necessary step in a feedback cycle of bar formation-destruction, a cycle driven by gas accretion.
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Athanassoula, E. "Evolution of Bars in Isolated and in Interacting Disk Galaxies." International Astronomical Union Colloquium 157 (1996): 309–20. http://dx.doi.org/10.1017/s0252921100049940.
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AbstractI use N-body simulations to follow the evolution of bars in both isolated and interacting disk galaxies. The pattern speeds of bars evolving in isolated galaxies decline gradually with time, due to transfer of angular momentum from the bar to other components in the galaxy. Both the form and amount of this decline depend on the model used. The fate of a bar in an interacting disk galaxy depends on the mass, central concentration and orbit of the perturber. The pattern speed, form and amplitude of the bar may change, the bar can become off-centered, or, more drastically, it can disappear altogether. Finally I propose a scenario for the evolution of NGC 7217, which could, if proven correct, explain the formation of the rings in that galaxy and also, at least qualitatively, the existence of a retrograde population.
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Géron, Tobias, R. J. Smethurst, Chris Lintott, et al. "The Effects of Bar Strength and Kinematics on Galaxy Evolution: Slow Strong Bars Affect Their Hosts the Most." Astrophysical Journal 973, no. 2 (2024): 129. http://dx.doi.org/10.3847/1538-4357/ad66b7.
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Abstract We study how bar strength and bar kinematics affect star formation in different regions of the bar by creating radial profiles of EW[Hα] and Dn4000 using data from Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA). Bars in galaxies are classified as strong or weak using Galaxy Zoo DESI, and they are classified as fast and slow bars using the Tremaine–Weinberg method on stellar kinematic data from the MaNGA survey. In agreement with previous studies, we find that strong bars in star-forming (SF) galaxies have enhanced star formation in their center and beyond the bar-end region, while star formation is suppressed in the arms of the bar. This is not found for weakly barred galaxies, which have very similar radial profiles to unbarred galaxies. In addition, we find that slow bars in SF galaxies have significantly higher star formation along the bar than fast bars. However, the global star formation rate is not significantly different between galaxies with fast and slow bars. This suggests that the kinematics of the bar do not affect star formation globally, but changes where star formation occurs in the galaxy. Thus, we find that a bar will influence its host the most if it is both strong and slow.
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Neumann, Justus, Francesca Fragkoudi, Isabel Pérez, et al. "Stellar populations across galaxy bars in the MUSE TIMER project." Astronomy & Astrophysics 637 (May 2020): A56. http://dx.doi.org/10.1051/0004-6361/202037604.
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Stellar populations in barred galaxies save an imprint of the influence of the bar on the host galaxy’s evolution. We present a detailed analysis of star formation histories (SFHs) and chemical enrichment of stellar populations in nine nearby barred galaxies from the TIMER project. We used integral field observations with the MUSE instrument to derive unprecedented spatially resolved maps of stellar ages, metallicities, [Mg/Fe] abundances, and SFHs, as well as Hα as a tracer of ongoing star formation. We find a characteristic V-shaped signature in the SFH that is perpendicular to the bar major axis, which supports the scenario where intermediate-age stars (∼2 − 6 Gyr) are trapped on more elongated orbits shaping a thinner part of the bar, while older stars (> 8 Gyr) are trapped on less elongated orbits shaping a rounder and thicker part of the bar. We compare our data to state-of-the-art cosmological magneto-hydrodynamical simulations of barred galaxies and show that such V-shaped SFHs arise naturally due to the dynamical influence of the bar on stellar populations with different ages and kinematic properties. Additionally, we find an excess of very young stars (< 2 Gyr) on the edges of the bars, predominantly on the leading side, thus confirming typical star formation patterns in bars. Furthermore, mass-weighted age and metallicity gradients are slightly shallower along the bar than in the disc, which is likely due to orbital mixing in the bar. Finally, we find that bars are mostly more metal-rich and less [Mg/Fe]-enhanced than the surrounding discs. We interpret this as a signature that the bar quenches star formation in the inner region of discs, usually referred to as star formation deserts. We discuss these results and their implications on two different scenarios of bar formation and evolution.
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Géron, Tobias, R. J. Smethurst, Hugh Dickinson, et al. "Galaxy Zoo CEERS: Bar Fractions Up to z ∼ 4.0." Astrophysical Journal 987, no. 1 (2025): 74. https://doi.org/10.3847/1538-4357/add7d0.
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Abstract We study the evolution of the bar fraction in disk galaxies between 0.5 < z < 4.0 using multiband colored images from JWST Cosmic Evolution Early Release Science Survey (CEERS). These images were classified by citizen scientists in a new phase of the Galaxy Zoo (GZ) project called GZ CEERS. Citizen scientists were asked whether a strong or weak bar was visible in the host galaxy. After considering multiple corrections for observational biases, we find that the bar fraction decreases with redshift in our volume-limited sample (n = 398); from 2 5 − 4 + 6 % at 0.5 < z < 1.0 to 3 − 1 + 6 % at 3.0 < z < 4.0. However, we argue it is appropriate to interpret these fractions as lower limits. Disentangling real changes in the bar fraction from detection biases remains challenging. Nevertheless, we find a significant number of bars up to z = 2.5. This implies that disks are dynamically cool or baryon dominated, enabling them to host bars. This also suggests that bar-driven secular evolution likely plays an important role at higher redshifts. When we distinguish between strong and weak bars, we find that the weak bar fraction decreases with increasing redshift. In contrast, the strong bar fraction is constant between 0.5 < z < 2.5. This implies that the strong bars found in this work are robust long-lived structures, unless the rate of bar destruction is similar to the rate of bar formation. Finally, our results are consistent with disk instabilities being the dominant mode of bar formation at lower redshifts, while bar formation through interactions and mergers is more common at higher redshifts.
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López Gómez, Alejandro, Ruslan Gabbasov, and Isaura Luisa Fuentes-Carrera. "Numerical Study of Bar Suppression in Galaxy Models Due to Disc Heating." Galaxies 13, no. 2 (2025): 45. https://doi.org/10.3390/galaxies13020045.
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The process of bar formation, evolution and destruction is still a controversial topic regarding galaxy dynamics. Numerical simulations show that these phenomena strongly depend on physical and numerical parameters. In this work, we study the combined influence of the softening parameter, ϵ and disc mass fraction, md, on the formation and evolution of bars in isolated disc-halo models via N-body simulations with different particle resolutions. Previous studies indicate that the bar strength depends on md as ∝md−1, which is seen as a delay in bar formation. However, the distorsion parameter, η, which measures the bar’s momentum through time, shows that an increase in md does not always induce a delay in bar formation. This suggests that ϵ interact to either enhance or weaken the bar. Moreover, numerical heating dominates in models with small softening values, creating highly accelerated particles at the centre of discs, regardless of md or resolution. These enhanced particle accelerations produce chaotic orbits for ϵ≤5 pc, resulting in bar suppression due to collisional dynamics in the centre. In our high-resolution models (N≈107), small softening values are incapable of reproducing the bar instability. The role of disc mass is as follows: increasing md for moderate ϵ (≥10 pc) reduces the amount of drift in the acceleration profile, without affecting the bar’s behaviour. Models with lower md values, coupled with small softening values, have an excess of highly accelerated particles, introducing unwanted effects into otherwise reliable simulations. Finally, we show that the evolution of the disc’s vertical acceleration profile is a reliable indicator of numerical heating introduced by ϵ and the bar.
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Fraser-McKelvie, Amelia, Alfonso Aragón-Salamanca, Michael Merrifield, et al. "SDSS-IV MaNGA: spatially resolved star formation in barred galaxies." Monthly Notices of the Royal Astronomical Society 495, no. 4 (2020): 4158–69. http://dx.doi.org/10.1093/mnras/staa1416.
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ABSTRACT Bars inhabit the majority of local-Universe disc galaxies and may be important drivers of galaxy evolution through the redistribution of gas and angular momentum within discs. We investigate the star formation and gas properties of bars in galaxies spanning a wide range of masses, environments, and star formation rates using the Mapping Nearby Galaxies at APO galaxy survey. Using a robustly defined sample of 684 barred galaxies, we find that fractional (or scaled) bar length correlates with the host’s offset from the star formation main sequence. Considering the morphology of the Hα emission we separate barred galaxies into different categories, including barred, ringed, and central configurations, together with Hα detected at the ends of a bar. We find that only low-mass galaxies host star formation along their bars, and that this is located predominantly at the leading edge of the bar itself. Our results are supported by recent simulations of massive galaxies, which show that the position of star formation within a bar is regulated by a combination of shear forces, turbulence, and gas flows. We conclude that the physical properties of a bar are mostly governed by the existing stellar mass of the host galaxy, but that they also play an important role in the galaxy’s ongoing star formation.
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Kataria, Sandeep Kumar, and Juntai Shen. "Importance of Initial Condition on Bar Secular Evolution: Role of Halo Angular Momentum Distribution Discontinuity." Astrophysical Journal 970, no. 1 (2024): 45. http://dx.doi.org/10.3847/1538-4357/ad5b58.
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Abstract The dark matter halo properties, for example, mass, spin, and concentration, play a significant role in the formation and evolution of bars in disk galaxies. This study highlights the importance of a new parameter: the dark matter halo angular momentum distribution in the disk’s central region. We experiment with N-body galaxy models having a disk and dark matter similar to Milky Way–type galaxies. In these models, we vary the discontinuity of the angular momentum distribution of the halo (the total spin is the same for all models). Our N-body experiments suggest that bar forms in all models after a few Gyr of disk evolution. However, in the secular evolution of the bar, as we evolve these models until 9.78 Gyr, the bar gains its strength in the model with the most continuous halo angular momentum distribution, and the bar loses strength for the most discontinuous halo angular momentum distribution. The secular evolution of the bar suggests that box/peanut/x-shaped bulges similar to those found in the Milky Way disk should be more pronounced in halos with continuous halo angular momentum distributions. This study demonstrates the importance of the initial condition setup of galaxy systems, namely the discontinuity in the dark matter halo angular momentum distribution for a given density distribution, on the bar secular evolution in the disk galaxy simulations. Further, this study helps reconcile the conflicting results of bar secular evolution in a high-spinning halo of the recent literature.
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Fraser-McKelvie, Amelia, Michael Merrifield, Alfonso Aragón-Salamanca, and Karen Masters. "Properties of barred galaxies in the MaNGA galaxy survey." Proceedings of the International Astronomical Union 14, S353 (2019): 226–30. http://dx.doi.org/10.1017/s1743921319008081.
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AbstractWe present the initial results of a census of 684 barred galaxies in the MaNGA galaxy survey. This large sample contains galaxies with a wide range of physical properties, and we attempt to link bar properties to key observables for the whole galaxy. We find the length of the bar, when normalised for galaxy size, is correlated with the distance of the galaxy from the star formation main sequence, with more passive galaxies hosting larger-scale bars. Ionised gas is observed along the bars of low-mass galaxies only, and these galaxies are generally star-forming and host short bars. Higher-mass galaxies do not contain Hα emission along their bars, however, but are more likely to host rings or Hα at the centre and ends of the bar. Our results suggest that different physical processes are at play in the formation and evolution of bars in low- and high-mass galaxies.
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Athanassoula, E. "Boxy/peanut and discy bulges: formation, evolution and properties." Proceedings of the International Astronomical Union 3, S245 (2007): 93–102. http://dx.doi.org/10.1017/s1743921308017389.
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AbstractThe class ‘bulges’ contains objects with very different formation and evolution paths and very different properties. I review two types of ‘bulges’, the boxy/peanut bulges (B/Ps) and the discy bulges. The former are parts of bars seen edge-on, have their origin in vertical instabilities of the disc and are somewhat shorter in extent than bars. Their stellar population is similar to that of the inner part of the disc from which they formed. Discy bulges have a disc-like outline, i.e., seen face-on they are circular or oval and seen edge-on they are thin. Their extent is of the order of 5 times smaller than that of the boxy/peanut bulges. They form from the inflow of mainly gaseous material to the centre of the galaxy and from subsequent star formation. They thus contain a lot of young stars and gas. Bulges of different types often coexist in the same galaxy. I review the main known results on these two types of bulges and present new simulation results.B/Ps form about 1Gyr after the bar, via a vertical buckling. At that time the bar strength decreases, its inner part becomes thicker – forming the peanut or boxy shape – and the ratio $\sigma_z^2/\sigma_r^2$ increases. A second buckling episode is seen in simulations with strong bars, also accompanied by a thickening of the peanut and a weakening of the bar. The properties of the B/Ps correlate strongly with those of the bar: stronger bars have stronger peanuts, a more flat-topped vertical density distribution and have experienced more bucklings.I also present simulations of disc galaxy formation, which include the formation of a discy bulge. Decomposition of their radial density profile into an exponential disc and a Sérsic bulge gives realistic values for the disc and bulge scale-lengths and mass ratios, and a Sérsic shape index of the order of 1.It is thus clear that classical bulges, B/P bulges and discy bulges are three distinct classes of objects and that lumping them together can lead to confusion. To avoid this, the two latter could be called B/P features and inner discs, respectively.
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Weinberg, Martin D. "Investigating the long-term evolution of galaxies: Noise, cuspy halos and bars." Symposium - International Astronomical Union 208 (2003): 215–26. http://dx.doi.org/10.1017/s0074180900207171.
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I review the arguments for the importance of halo structure in driving galaxy evolution and coupling a galaxy to its environment. We begin with a general discussion of the key dynamics and examples of structure dominated by modes. We find that simulations with large numbers of particles (N ≳ 106) are required to resolve the dynamics. Finally, I will describe some new results which demonstrates that a disk bar can produce cores in a cuspy CDM dark-matter profile within a gigayear. An inner Lindblad-like resonance couples the rotating bar to halo orbits at all radii through the cusp, rapidly flattening it. This resonance disappears for profiles with cores and is responsible for a qualitative difference in bar-driven halo evolution with and without a cusp. Although the bar gives up the angular momentum in its pattern to make the core, the formation epoch is rich in accretion events to recreate or trigger a classic stellar bar. The evolution of the cuspy inner halo by the first-generation bar paves the way for a long-lived subsequent bar with low torque and a stable pattern speed.
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Pérez, I., I. Martínez-Valpuesta, T. Ruiz-Lara, et al. "Observational constraints to boxy/peanut bulge formation time." Monthly Notices of the Royal Astronomical Society: Letters 470, no. 1 (2017): L122—L126. http://dx.doi.org/10.1093/mnrasl/slx087.
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Abstract Boxy/peanut bulges are considered to be part of the same stellar structure as bars and both could be linked through the buckling instability. The Milky Way is our closest example. The goal of this Letter is to determine if the mass assembly of the different components leaves an imprint in their stellar populations allowing the estimation the time of bar formation and its evolution. To this aim, we use integral field spectroscopy to derive the stellar age distributions, SADs, along the bar and disc of NGC 6032. The analysis clearly shows different SADs for the different bar areas. There is an underlying old (≥12 Gyr) stellar population for the whole galaxy. The bulge shows star formation happening at all times. The inner bar structure shows stars of ages older than 6 Gyr with a deficit of younger populations. The outer bar region presents an SAD similar to that of the disc. To interpret our results, we use a generic numerical simulation of a barred galaxy. Thus, we constrain, for the first time, the epoch of bar formation, the buckling instability period and the posterior growth from disc material. We establish that the bar of NGC 6032 is old, formed around 10 Gyr ago while the buckling phase possibly happened around 8 Gyr ago. All these results point towards bars being long-lasting even in the presence of gas.
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Zurita, A., E. Florido, I. Pérez, P. Coelho, and D. A. Gadotti. "Bar effects on ionized gas properties and dust content in galaxy centers." Proceedings of the International Astronomical Union 10, S309 (2014): 356. http://dx.doi.org/10.1017/s1743921314010473.
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AbstractObservations and simulations indicate that bars are important agents to transfer material towards galaxy centers. However, observational studies devoted to investigate the effects of bars in galaxy centers are not yet conclusive. We have used a sample (Coelho & Gadotti 2011) of nearby face–on galaxies with available spectra (SDSS database) to investigate the footprints of bars in galaxy centers by analysing the central ionized gas properties of barred and unbarred galaxies separately. We find statistically significant differences in the Hβ Balmer extinction, star formation rate per unit area, in the [S ii]λ6717/[S ii]λ6731 line ratio, and notably in the N2 parameter (N2 = log([N ii]λ6583/Hα)). A deeper analysis reflects that these differences are only relevant for the less massive bulges (≲1010M⊙). These results have important consequences for studies on bulge formation and galaxy evolution.
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Rosas-Guevara, Yetli, Silvia Bonoli, Massimo Dotti, et al. "The evolution of the barred galaxy population in the TNG50 simulation." Monthly Notices of the Royal Astronomical Society 512, no. 4 (2022): 5339–57. http://dx.doi.org/10.1093/mnras/stac816.
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ABSTRACT We use the magnetic-hydrodynamical simulation TNG50 to study the evolution of barred massive disc galaxies. Massive spiral galaxies are already present as early as z = 4, and bar formation takes place already at those early times. The bars grow longer and stronger as the host galaxies evolve, with the bar sizes increasing at a pace similar to that of the disc scalelengths. The bar fraction mildly evolves with redshift for galaxies with $M_{*}\ge 10^{10}\rm M_{\odot }$, being greater than $\sim 40{{\ \rm per\ cent}}$ at 0.5 &lt; z &lt; 3 and $\sim 30{{\ \rm per\ cent}}$ at z = 0. When bars larger than a given physical size ($\ge 2\, \rm kpc$) or the angular resolution limit of twice the I-band angular PSF FWHM of the HST are considered, the bar fraction dramatically decreases with increasing redshift, reconciling the theoretical predictions with observational data. We find that barred galaxies have an older stellar population, lower gas fractions, and star formation rates than unbarred galaxies. In most cases, the discs of barred galaxies assembled earlier and faster than the discs of unbarred galaxies. We also find that barred galaxies are typical in haloes with larger concentrations and smaller spin parameters than unbarred galaxies. Furthermore, the inner regions of barred galaxies are more baryon-dominated than those of unbarred galaxies but have comparable global stellar mass fractions. Our findings suggest that the bar population could be used as a potential tracer of the buildup of disc galaxies and their host haloes. With this paper, we release a catalogue of barred galaxies in TNG50 at six redshifts between z = 4 and 0.
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Norman, C. A., H. Hasan, and J. A. Sellwood. "Bar dissolution and bulge formation." Symposium - International Astronomical Union 171 (1996): 427. http://dx.doi.org/10.1017/s0074180900233457.
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We discuss the general classification of secular evolution in galaxies into terms of stellar dynamics. We present two-dimensional N-body simulations of a disk galaxy in which a central mass concentration is imposed after the formation of a strong bar. We show that the bar dissolves almost completely if the central mass concentration exceeds approximately 5% of the combined disk and bulge mass. This behavior can be understood in terms of previous work on single particle orbits (Hasan & Norman 1990, Hasan et al. 1993); the sustaining orbits aligned with the bar become stochastic as the Inner Lindblad resonance moves out past the minor axis of the bar. We present arguments that bar formation and subsequent thickening and dissolution will create a bulge-like stellar distribution from the central part of the disk. We discuss the predictions of such a model including the point that barred Scs with sufficient central mass concentrations should be building bulges now. We emphasize that bulges can come from a number of different mechanisms and we discuss the current evidence at both high and low redshift.
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Tawfeek, Amira A., Bernardo Cervantes Sodi, Jacopo Fritz, et al. "Morphology Driven Evolution of Barred Galaxies in OMEGAWINGS Clusters." Astrophysical Journal 940, no. 1 (2022): 1. http://dx.doi.org/10.3847/1538-4357/ac9976.
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Abstract We present a study of barred galaxies in the cluster environment, exploiting a sample of galaxies drawn from the extended WIde-field Nearby Galaxy-cluster Survey (OmegaWINGS) that covers up to the outer regions of 32 local X-ray selected clusters. Barred galaxies are identified through a semiautomatic analysis of ellipticity and position angle profiles. We find, in agreement with previous studies, a strong codependence of the bar fraction with the galaxy stellar mass and morphological type, being maximum for massive late-type galaxies. The fraction of barred galaxies decreases with increasing cluster mass and with decreasing clustercentric distance, a dependence that vanishes once we control for morphological type, which indicates that the likelihood of a galaxy hosting a bar in the cluster environment is determined by its morphological transformation. At large clustercentric distances, we detect a dependence on the distance to the nearest neighbor galaxy, suggesting that tidal forces with close companions are able to suppress the formation of bars or even destroy them. Barred galaxies in our sample are either early-type, star-forming galaxies located within the virial radii of the clusters or late-type quenched galaxies found beyond the virial radii of the clusters. We propose a scenario in which already quenched barred galaxies that fall into the clusters are centrally rejuvenated by the interplay of the perturbed gas by ram pressure and the bar, in galaxies that are undergoing a morphological transformation.
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Semczuk, Marcin, Walter Dehnen, Ralph Schönrich, and E. Athanassoula. "Pattern speed evolution of barred galaxies in TNG50." Astronomy & Astrophysics 692 (December 2024): A159. https://doi.org/10.1051/0004-6361/202451521.
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Context. Galactic bars are found in the majority of disc galaxies. They rotate nearly rigidly with an angular frequency called pattern speed. In idealised simulations, the bar pattern speed generally decreases with time due to dynamical friction exerted by the dark-matter halo, while cold gas can reduce or even reverse this trend. Aims. We want to understand how different galaxy properties affect the evolution of the bar pattern speed in more realistic situations, including ongoing star formation, mass infall, active galactic nucleus (AGN) feedback, and galaxy interactions. Methods. We traced the pattern-speed evolution of simulated bars in the TNG50-1 cosmological simulations. Results. Simulated bars with an initially high pattern speed and a subsequent rapid slowdown are more likely found in more massive galaxies. Lower mass galaxies, on the other hand, preferentially host bars that start at relatively low pattern speeds and retain the same value until the end of the simulation. More massive simulated barred galaxies are also more affected by the AGN-feedback model, which very efficiently removes the cold gas that could have prevented the slowdown. Conclusions. We find that bars grow and strengthen with slowdown, in agreement with higher resolution simulations. We find that strong correlations between the bar slowdown rate and galaxy mass weaken considerably when we use dimensionless measures to quantify the slowdown. In TNG50, the AGN-feedback prescription amplifies the mass dependence. Turned around, this provides an interesting statistic to constrain sub-grid physics by bar growth and slowdown.
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Freeman, K. C. "The Evolutionary History of the Milky Way." Symposium - International Astronomical Union 171 (1996): 3–10. http://dx.doi.org/10.1017/s0074180900232087.
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The accretion of small satellite galaxies appears to have been important in the formation of the metal-poor halo of the Galaxy. The disrupting Sgr dwarf galaxy and the recent discovery of a young, metal-poor component of the halo indicate that this is a continuing process. The evolution of the galactic disk, and some consequences of the bar-like nature of the galactic bulge are briefly discussed.
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Lingard, Timothy, Karen L. Masters, Coleman Krawczyk, et al. "Galaxy zoo builder: Morphological dependence of spiral galaxy pitch angle." Monthly Notices of the Royal Astronomical Society 504, no. 3 (2021): 3364–74. http://dx.doi.org/10.1093/mnras/stab1072.
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ABSTRACT Spiral structure is ubiquitous in the Universe, and the pitch angle of arms in spiral galaxies provide an important observable in efforts to discriminate between different mechanisms of spiral arm formation and evolution. In this paper, we present a hierarchical Bayesian approach to galaxy pitch angle determination, using spiral arm data obtained through the Galaxy Builder citizen science project. We present a new approach to deal with the large variations in pitch angle between different arms in a single galaxy, which obtains full posterior distributions on parameters. We make use of our pitch angles to examine previously reported links between bulge and bar strength and pitch angle, finding no correlation in our data (with a caveat that we use observational proxies for both bulge size and bar strength which differ from other work). We test a recent model for spiral arm winding, which predicts uniformity of the cotangent of pitch angle between some unknown upper and lower limits, finding our observations are consistent with this model of transient and recurrent spiral pitch angle as long as the pitch angle at which most winding spirals dissipate or disappear is larger than 10°.
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Nogueira-Cavalcante, J. P., R. Dupke, P. Coelho, et al. "J-PLUS: Impact of bars on quenching timescales in nearby green valley disc galaxies." Astronomy & Astrophysics 630 (September 25, 2019): A88. http://dx.doi.org/10.1051/0004-6361/201935138.
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Context. Between the blue cloud and the red sequence peaks on the galaxy colour–magnitude diagram there is a region sparsely populated by galaxies called the green valley. In a framework where galaxies mostly migrate on the colour–magnitude diagram from star forming to quiescent, the green valley is considered a transitional galaxy stage. The details of the processes that drive galaxies from star-forming to passive systems still remain unknown. Aims. We aim to measure the transitional timescales of nearby galaxies across the green valley, through the analysis of Galaxy Evolution Explorer and Javalambre Photometric of Local Universe Survey photometric data. Specifically, we seek to study the impact of bars on the quenching timescales. Methods. We developed a method that estimates empirically the star formation quenching timescales of green valley galaxies, assuming an exponential decay model of the star formation histories and through a combination of narrow and broad bands from the Javalambre Photometric of Local Universe Survey and Galaxy Evolution Explorer. We correlated these quenching timescales with the presence of bars. Results. We find that the Javalambre Photometric of Local Universe Survey colours F0395 −g and F0410 −g are sensitive to different star formation histories, showing, consequently, a clear correlation with the Dn(4000) and Hδ, A spectral indices. We measured quenching timescales based on these colours and we find that quenching timescales obtained with our new approach are in agreement with those determined using spectral indices. We also compared the quenching timescales of green valley disc galaxies as a function of the probability of hosting a bar. We find that galaxies with high bar probability tend to quench their star formation slowly. Conclusions. We conclude that: (1) Javalambre Photometric of Local Universe Survey filters can be used to measure quenching timescales in nearby green valley galaxies; and (2) the resulting star formation quenching timescales are longer for barred green valley galaxies. Considering that the presence of a bar indicates that more violent processes (e.g. major mergers) are absent in host galaxies, we conclude that the presence of a bar can be used as a morphological signature for slow star formation quenching.
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Fraser-McKelvie, Amelia, Michael Merrifield, Alfonso Aragón-Salamanca, et al. "SDSS-IV MaNGA: The link between bars and the early cessation of star formation in spiral galaxies." Monthly Notices of the Royal Astronomical Society 499, no. 1 (2020): 1116–25. http://dx.doi.org/10.1093/mnras/staa2866.
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ABSTRACT Bars are common in low-redshift disc galaxies, and hence quantifying their influence on their host is of importance to the field of galaxy evolution. We determine the stellar populations and star formation histories of 245 barred galaxies from the Mapping Nearby Galaxies at APO (MaNGA) galaxy survey, and compare them to a mass- and morphology-matched comparison sample of unbarred galaxies. At fixed stellar mass and morphology, barred galaxies are optically redder than their unbarred counterparts. From stellar population analysis using the full spectral fitting code starlight, we attribute this difference to both older and more metal-rich stellar populations. Dust attenuation however, is lower in the barred sample. The star formation histories of barred galaxies peak earlier than their non-barred counterparts, and the galaxies build up their mass at earlier times. We can detect no significant differences in the local environment of barred and unbarred galaxies in this sample, but find that the H i gas mass fraction is significantly lower in high-mass ($\rm {M}_{\star } \gt 10^{10}~\rm {M}_{\odot }$) barred galaxies than their non-barred counterparts. We speculate on the mechanisms that have allowed barred galaxies to be older, more metal-rich and more gas-poor today, including the efficient redistribution of galactic fountain byproducts, and a runaway bar formation scenario in gas-poor discs. While it is not possible to fully determine the effect of the bar on galaxy quenching, we conclude that the presence of a bar and the early cessation of star formation within a galaxy are intimately linked.
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Fujimoto, Yusuke, Fumiya Maeda, Asao Habe, and Kouji Ohta. "Fast cloud–cloud collisions in a strongly barred galaxy: suppression of massive star formation." Monthly Notices of the Royal Astronomical Society 494, no. 2 (2020): 2131–46. http://dx.doi.org/10.1093/mnras/staa840.
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ABSTRACT Recent galaxy observations show that star formation activity changes depending on galactic environments. In order to understand the diversity of galactic-scale star formation, it is crucial to understand the formation and evolution of giant molecular clouds in an extreme environment. We focus on observational evidence that bars in strongly barred galaxies lack massive stars even though quantities of molecular gas are sufficient to form stars. In this paper, we present a hydrodynamical simulation of a strongly barred galaxy, using a stellar potential which is taken from observational results of NGC 1300, and we compare cloud properties between different galactic environments: bar, bar-end, and spiral arms. We find that the mean of cloud’s virial parameter is αvir ∼ 1 and that there is no environmental dependence, indicating that the gravitationally bound state of a cloud is not behind the observational evidence of the lack of massive stars in strong bars. Instead, we focus on cloud–cloud collisions, which have been proposed as a triggering mechanism for massive star formation. We find that the collision speed in the bar is faster than those in the other regions. We examine the collision frequency using clouds’ kinematics and conclude that the fast collisions in the bar could originate from random-like motion of clouds due to elliptical gas orbits shifted by the bar potential. These results suggest that the observed regions of lack of active star formation in the strong bar originate from the fast cloud–cloud collisions, which are inefficient in forming massive stars, due to the galactic-scale violent gas motion.
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Mundell, C. G., A. Pedlar, D. L. Shone, D. J. Axon, J. Meaburn, and S. W. Unger. "NGC 3227 - An Interacting Barred Spiral with an Active Nucleus." International Astronomical Union Colloquium 157 (1996): 473–75. http://dx.doi.org/10.1017/s0252921100050259.
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Recently, bars have become a favored mechanism for transporting material at larger radii towards the nuclei of active galaxies, with the possibility of inflowing gas (on kiloparsec scales) accumulating in circumnuclear rings, bar-like features or structures reminiscent of spiral arms. In addition, it seems clear that interactions play some role in the triggering and fuelling of nuclear activity, as well as in the formation and evolution of galactic bars. NGC 3227 is a barred Seyfert galaxy which appears to be interacting with the nearby elliptical galaxy NGC 3226. The NGC 3227 system thus appears to be an excellent ”laboratory case“ in which to study the relationship between the bar phenomenon, and an active nucleus in an interacting system.
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Zee, Woong-Bae G., Sanjaya Paudel, Jun-Sung Moon, and Suk-Jin Yoon. "Unraveling Joint Evolution of Bars, Star Formation, and Active Galactic Nuclei of Disk Galaxies." Astrophysical Journal 949, no. 2 (2023): 91. http://dx.doi.org/10.3847/1538-4357/acc79a.
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Abstract We aim to unravel the interplay between bars, star formation (SF), and active galactic nuclei (AGNs) in barred galaxies. To this end, we utilize the SDSS DR12 to select a sample of nearby (0.02 < z < 0.06) disk galaxies that are suitable for bar examination (M r < −20.12 and inclination ≲53°). We identify 3662 barred galaxies and measure the length and axis ratio of each bar. We invent new bar parameters that mitigate the stellar and bulge mass biases and show, for the first time, that the evolution of non-AGN and AGN-hosting barred galaxies should be tracked using different bar parameters: the bar length for non-AGN galaxies and the bar axis ratio for AGN-hosting galaxies. Our analysis confirms that barred galaxies have a higher specific SF rate than unbarred control galaxies. Moreover, we find a positive correlation of bar length with both the SF enhancement and the centrally star-forming galaxy fraction, indicating the interconnectivity of bars and SF through the bar-driven gas inflow. We also find that, while the AGN fraction of barred galaxies is the same as that of the unbarred control sample, galaxies hosting more massive black holes (BHs) have rounder (i.e., higher axis ratio) bars, implying that the bar is not a cause of AGN activity; rather, AGNs appear to regulate bars. Our findings corroborate theoretical predictions that bars in non-AGN galaxies grow in length, and bars in AGN-hosting galaxies become rounder as BHs grow and eventually get destroyed.
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Chantavat, T., S. Yuma, P. Malelohit, and T. Worrakitpoonpon. "Morphological Evolution of Disk Galaxies and Their Concentration, Asymmetry, and Clumpiness (CAS) Properties in Simulations across Toomre’s Q Parameter." Astrophysical Journal 965, no. 1 (2024): 77. http://dx.doi.org/10.3847/1538-4357/ad3218.
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Abstract We investigate the morphological and structural evolution of disk galaxies in simulations for a wide range of Toomre’s Q parameters. In addition to the inspection of conventional bar modes, we compute the concentration, asymmetry, and clumpiness (CAS) parameters to enlarge the understanding of the galaxy evolution. These parameters are widely employed to analyze the light distribution of the observed galaxies, but the adaptation to numerical simulations is not much considered. While the bar formation takes place in a considerable range of Q around 1, barred galaxies originating from Q > 1 and Q < 1 disks yield CAS values that differ significantly. Disks starting with Q < 1 develop clumps due to local gravitational instabilities along with the bar, and these clumps play a central role in enhancing the CAS values. This process is absent in the Q > 1 counterparts in which the evolution is dominated by linearly unstable two-armed modes that lead to lower CAS values. Likewise, unbarred galaxies that are obtainable from disks with Q far below and far above 1 exhibit greatly different CAS magnitudes. It turns out that the CAS parameters can serve as indicators of the initial kinematical state and the evolution history of a disk of any morphology. In addition, we find an alternative mechanism of the formation of the lopsided barred galaxy when Q ≲ 1. Bars that evolve in the midst of the clumps can spontaneously become lopsided at the end.
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Combes, Françoise. "The role of external gas accretion on galaxy transformations, and evidence of such accretion." Proceedings of the International Astronomical Union 10, H16 (2012): 366. http://dx.doi.org/10.1017/s1743921314011387.
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AbstractContinuously accreting matter from cosmic filaments is one of the main way to assemble mass for galaxies (Keres et al.2005, Dekel et al.2009). This external accretion accelerates secular processes, and maintain star formation, but also bar and spiral formation (Bournaud & Combes 2002), and consequent radial migration. Secular evolution may alleviate the problem of too massive bulge formation in the standard LCDM hierarchical scenario. Inside out formation of galaxies may account for the evolution of the size-mass relation and evolution with redshift. I will show how gas accretion from the inter galactic medium can mimick perturbations due to galaxy interactions (cf Figure 1), and I will describe evidence of such accretion, through warps, polar rings or damped Lyman-α systems.
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Zana, Tommaso, Pedro R. Capelo, Massimo Dotti, et al. "Barred galaxies in cosmological zoom-in simulations: the importance of feedback." Monthly Notices of the Royal Astronomical Society 488, no. 2 (2019): 1864–77. http://dx.doi.org/10.1093/mnras/stz1834.
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Abstract Bars are a key factor in the long-term evolution of spiral galaxies, in their unique role in redistributing angular momentum and transporting gas and stars on large scales. The Eris-suite simulations are cosmological zoom-in, N-body, smoothed-particle hydrodynamic simulations built to follow the formation and evolution of a Milky-Way-sized galaxy across the build-up of the large-scale structure. Here we analyse and describe the outcome of two particular simulations taken from the Eris suite – ErisBH and Eris2k – which mainly differ in the prescriptions employed for gas cooling, star formation, and feedback from supernovae and black holes. Our study shows that the enhanced effective feedback in Eris2k, due to the collective effect of the different micro-physics implementations, results in a galaxy that is less massive than its ErisBH counterpart till z ∼ 1. However, when the stellar content is large enough so that global dynamical instabilities can be triggered, the galaxy in Eris2k develops a stronger and more extended bar with respect to ErisBH. We demonstrate that the structural properties and time evolution of the two bars are very different. Our results highlight the importance of accurate sub-grid prescriptions in cosmological zoom-in simulations of the process of galaxy formation and evolution, and the possible use of a statistical sample of barred galaxies to assess the strength of the stellar feedback.
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Athanassoula, E. "Isolated and Interacting Galaxies: Simulations with GRAPE." Symposium - International Astronomical Union 208 (2003): 177–88. http://dx.doi.org/10.1017/s0074180900207134.
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I present N-body simulations of isolated and interacting galaxies, made on GRAPE machines. In particular I discuss the formation and evolution of N-body bars and compare their properties to those of bars in early-type and late-type galactic discs. I argue that the halo can help the bar grow, contrary to previous beliefs, by taking positive angular momentum from it via its resonant stars. I then focus on the interaction and subsequent merging of a barred disc galaxy with a spheroidal satellite. The evolution depends strongly on the mass (density) of the satellite and may lead to its destruction or to the destruction of the bar.
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Peterken, Thomas, Amelia Fraser-McKelvie, Alfonso Aragón-Salamanca, et al. "Time-slicing spiral galaxies with SDSS-IV MaNGA." Monthly Notices of the Royal Astronomical Society 489, no. 1 (2019): 1338–43. http://dx.doi.org/10.1093/mnras/stz2204.
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ABSTRACT Spectra of galaxies contain a wealth of information about the stellar populations from which they are made. With integral field unit (IFU) surveys, such data can be used to map out stellar population properties across the face of a galaxy, allowing one to go beyond simple radial profiles and study details of non-axisymmetric structure. To-date, however, such studies have been limited by the quality of available data and the power of spectral analysis tools. We now take the next step and study the barred spiral galaxy MCG + 07-28-064 from observations obtained as part of the SDSS-IV MaNGA project. We find that we can decompose this galaxy into ‘time slices,’ which reveal the varying contributions that stars of differing ages make to its bar and spiral structure, offering new insight into the evolution of these features. We find evidence for the ongoing growth of the bar, including the most recent star formation on its leading edge, and for the underlying density wave responsible for spiral structure. This pilot study indicates that there is a wealth of untapped information on the spatial distribution of star formation histories available in the current generation of IFU galaxy surveys.
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Łokas, Ewa L. "Anatomy of a buckling galactic bar." Astronomy & Astrophysics 629 (September 2019): A52. http://dx.doi.org/10.1051/0004-6361/201936056.
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Using N-body simulations we study the buckling instability in a galactic bar forming in a Milky Way-like galaxy. The galaxy is initially composed of an axisymmetric, exponential stellar disk embedded in a spherical dark matter halo. The parameters of the model are chosen so that the galaxy is mildly unstable to bar formation and the evolution is followed for 10 Gyr. A strong bar forms slowly over the first few gigayears and buckles after 4.5 Gyr from the start of the simulation becoming much weaker and developing a pronounced boxy/peanut shape. We measure the properties of the bar at the time of buckling in terms of the mean acceleration, velocity, and distortion in the vertical direction. The maps of these quantities in face-on projections reveal characteristic quadrupole patterns which wind up over a short timescale. We also detect a secondary buckling event lasting much longer and occurring only in the outer part of the bar. We then study the orbital structure of the bar in periods before and after the first buckling. We find that most of the buckling orbits originate from x1 orbits supporting the bar. During buckling the ratio of the vertical to horizontal frequency of the stellar orbits decreases dramatically and after buckling the orbits obey a very tight relation between the vertical and circular frequency: 3ν = 4Ω. We propose that buckling is initiated by the vertical resonance of the x1 orbits creating the initial distortion of the bar that later evolves as kinematic bending waves.
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Gadotti, Dimitri A., Adrian Bittner, Jesus Falcón-Barroso, and Jairo Méndez-Abreu. "Kinematical signatures of disc instabilities and secular evolution in the MUSE TIMER Survey." Proceedings of the International Astronomical Union 14, S353 (2019): 135–39. http://dx.doi.org/10.1017/s1743921319008585.
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AbstractThe MUSE TIMER Survey has obtained high signal and high spatial resolution integral-field spectroscopy data of the inner ~ 6×6 kpc of 21 nearby massive disc galaxies. This allows studies of the stellar kinematics of the central regions of massive disc galaxies that are unprecedented in spatial resolution. We confirm previous predictions from numerical and hydrodynamical simulations of the effects of bars and inner bars on stellar and gaseous kinematics, and also identify box/peanuts via kinematical signatures in mildly and moderately inclined galaxies, including a box/peanut in a face-on inner bar. In 20/21 galaxies we find inner discs and show that their properties are fully consistent with the bar-driven secular evolution picture for their formation. In addition, we show that these inner discs have, in the region where they dominate, larger rotational support than the main galaxy disc, and discuss how their stellar population properties can be used to estimate when in cosmic history the main bar formed. Our results are compared with photometric studies in the context of the nature of galaxy bulges and we show that inner discs are identified in image decompositions as photometric bulges with exponential profiles (i.e., Sérsic indices near unity).
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Jang, Dajeong, and Woong-Tae Kim. "Effects of the Central Mass Concentration on Bar Formation in Disk Galaxies." Astrophysical Journal 942, no. 2 (2023): 106. http://dx.doi.org/10.3847/1538-4357/aca7bc.
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Abstract While bars are common in disk galaxies, their formation conditions are not well understood. We use N-body simulations to study the formation and evolution of a bar in isolated galaxies consisting of a stellar disk, a classical bulge, and a dark halo. We consider 24 galaxy models that are similar to the Milky Way but differ in the mass and compactness of the classical bulge and halo concentration. We find that the bar formation requires ( Q T , min / 1.2 ) 2 + ( CMC / 0.05 ) 2 ≲ 1 , where Q T , min and CMC refer to the minimum value of the Toomre stability parameter and the central mass concentration, respectively. Bars tend to be stronger and longer, and to rotate more slowly, in galaxies with a less massive and less compact bulge and halo. All bars formed in our models correspond to slow bars. A model with the bulge mass of ∼10%–20% of the disk under a concentrated halo produces a bar similar to that of the Milky Way. We discuss our findings in relation to other bar formation criteria suggested by previous studies.
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Ansar, Sioree, and Mousumi Das. "The Stellar Bar–Dark Matter Halo Connection in the TNG50 Simulations." Astrophysical Journal 975, no. 2 (2024): 243. http://dx.doi.org/10.3847/1538-4357/ad7a6b.
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Abstract Stellar bars in disk galaxies grow as stars in near-circular orbits lose angular momentum to their environments, including their dark matter (DM) halo, and transform into elongated bar orbits. This angular momentum exchange during galaxy evolution hints at a connection between bar properties and the DM halo spin λ, the dimensionless form of DM angular momentum. We investigate the connection between halo spin λ and galaxy properties in the presence/absence of stellar bars, using the cosmological magnetohydrodynamic TNG50 simulations at multiple redshifts (0 < z r < 1). We determine the bar strength (or bar amplitude, A 2/A 0), using Fourier decomposition of the face-on stellar density distribution. We determine the halo spin for barred and unbarred galaxies (0 < A 2/A 0 < 0.7) in the center of the DM halo, close to the galaxy’s stellar disk. At z r = 0, there is an anticorrelation between halo spin and bar strength. Strongly barred galaxies (A 2/A 0 > 0.4) reside in DM halos with low spin and low specific angular momentum at their centers. In contrast, unbarred/weakly barred galaxies (A 2/A 0 < 0.2) exist in halos with higher central spin and higher specific angular momentum. The anticorrelation is due to the barred galaxies’ higher DM mass and lower angular momentum than the unbarred galaxies at z r = 0, as a result of galaxy evolution. At high redshifts (z r = 1), all galaxies have higher halo spin compared to those at lower redshifts (z r = 0), with a weak anticorrelation for galaxies having A 2/A 0 > 0.2. The formation of DM bars in strongly barred systems highlights how angular momentum transfer to the halo can influence its central spin.
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Staveley-Smith, L. "Michigan 160: a precursor to the LMC?" Symposium - International Astronomical Union 148 (1991): 376–77. http://dx.doi.org/10.1017/s0074180900200910.
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The tidal interaction between the Magellanic Clouds and the Galaxy is an important factor in influencing the physical and dynamical evolution of the Clouds (e.g. the Magellanic Stream) as well as the genesis and evolution of their respective stellar populations. However, how important is the influence of the Galaxy? This is a key question since we know that relatively isolated, magellanic-type galaxies do exist (e.g. NGC 3109 and NGC 4449) and have been just as efficient at star-formation as the LMC. It is possible in fact that the star formation in the clouds is primarily stochastic in nature and is relatively insensitive to the global forces which seem to have shaped stellar formation processes in massive spiral and elliptical galaxies. Unsupported by a massive bulge or halo component, cold gas disks are inherently susceptible to radial and bar-like instabilities (Efstathiou et al. 1982) which are very efficient at creating the dynamical pressures required for rapid star-formation. With this in mind, a detailed comparison of 'field' magellanic-type galaxies with the LMC and SMC is of some importance.
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Wozniak, Hervé. "Diffusion of radial action in a galactic disc." Astronomy & Astrophysics 642 (October 2020): A207. http://dx.doi.org/10.1051/0004-6361/202038959.
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Context. The stellar migration of the galactic disc stars has been invoked to explain the dispersion of stellar metallicity observed in the solar neighbourhood. Aims. We seek to identify the dynamical mechanisms underlying stellar migration in an isolated galaxy disc under the influence of a bar. Our approach is to analyse the diffusion of dynamical quantities. Methods. We extend our previous work by exploring Chirikov’s diffusion rate (and derived timescale) of the radial action JR in an idealised N-body simulation of an isolated disc galaxy. We limit our study to the evolution of the disc region well after the formation of the bar, in a regime of adiabatic evolution. Results. The JR diffusion timescale TD(JR) is less than 3 Gyr for roughly half the galaxy mass. It is always much shorter than the angular momentum diffusion timescale TD(Lz) outside the stellar bar. In the disc, ⟨TD(JR)⟩ ∼ 1 Gyr. All non-axisymmetric morphological structures that are characteristic of resonances and waves in the disc are associated to particles with TD(JR) < 3 Gyr and TD(Lz) > 10 Gyr. Short TD(JR) can be explained by the gradual de-circularisation of initially circular orbits (JR = 0) under the effect of intermittent. Inner Linblad resonance scattering by wave trains propagating in the disc, well beyond the outer Lindblad resonance of the bar (OLR). This leads to a moderate secular heating of the disc beyond the bar’s OLR for 7 Gyr, which is comparable to solar neighbourhood observations. The complex multi-wave structure, mixing permanent and intermittent modes, allows for multiple resonance overlaps.
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Fortune-Bashee, Xena, Jiayi 嘉懿 Sun 孙, and Jonathan C. Tan. "The Impact of Shear on Disk Galaxy Star Formation Rates." Astrophysical Journal Letters 977, no. 1 (2024): L6. https://doi.org/10.3847/2041-8213/ad91a3.
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Abstract Determining the physical processes that control galactic-scale star formation rates is essential for an improved understanding of galaxy evolution. The role of orbital shear is currently unclear, with some models expecting reduced star formation rates and efficiencies with increasing shear, e.g., if shear stabilizes gas against gravitational collapse, while others predicting enhanced rates, e.g., if shear-driven collisions between giant molecular clouds trigger star formation. Expanding on the analysis of 16 galaxies by C. Suwannajak et al., we assess the shear dependence of star formation efficiency (SFE) per orbital time (ϵ orb) in 49 galaxies selected from the PHANGS-ALMA survey. In particular, we test a prediction of the shear-driven giant molecular cloud (GMC) collision model that ϵ orb ∝ (1–0.7β), where β ≡ d ln v circ / d ln r , i.e., SFE per orbital time declines with decreasing shear. We fit the function ϵ orb = ϵ orb,0(1 − α CC β) finding α CC ≃ 0.76 ± 0.16; an alternative fit with ϵ orb normalized by the median value in each galaxy yields α CC * = 0.80 ± 0.15 . These results are in good agreement with the prediction of the shear-driven GMC collision theory. We also examine the impact of a galactic bar on ϵ orb finding a modest decrease in SFE in the presence of a bar, which can be attributed to lower rates of shear in these regions. We discuss the implications of our results for the GMC life cycle and environmental dependence of star formation activity.
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Najarro, Francisco, J. S. Clark, Marcus Lohr, et al. "Infrared studies of the massive stellar population at the Galactic Center and the inner disk." Proceedings of the International Astronomical Union 18, S361 (2022): 114–15. http://dx.doi.org/10.1017/s1743921322003052.
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AbstractWe present results from our ongoing infrared spectroscopic studies of the massive stellar content at the Center of the Milky Way (GC) and across the obscured Galactic disk. Together with the full characterization of these clusters, we seek to obtain a present day metallicity 2-D map of the inner Galaxy and characterize the influence on the bar in the chemical evolution. We will also constrain the clusters IMFs, infer the presence of possible top-heavy recent star formation histories and test massive star formation channels: clusters vs isolation.
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Gadotti, Dimitri A., Adrian Bittner, Jesús Falcón-Barroso, et al. "Kinematic signatures of nuclear discs and bar-driven secular evolution in nearby galaxies of the MUSE TIMER project." Astronomy & Astrophysics 643 (October 27, 2020): A14. http://dx.doi.org/10.1051/0004-6361/202038448.
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The central regions of disc galaxies hold clues to the processes that dominate their formation and evolution. To exploit this, the TIMER project has obtained high signal-to-noise and spatial resolution integral-field spectroscopy data of the inner few kpc of 21 nearby massive barred galaxies, which allows studies of the stellar kinematics in their central regions with unprecedented spatial resolution. We confirm theoretical predictions of the effects of bars on stellar kinematics and identify box/peanuts through kinematic signatures in mildly and moderately inclined galaxies, finding a lower limit to the fraction of massive barred galaxies with box/peanuts at ∼62%. Further, we provide kinematic evidence of the connection between barlenses, box/peanuts, and bars. We establish the presence of nuclear discs in 19 galaxies and show that their kinematics are characterised by near-circular orbits with low pressure support and that they are fully consistent with the bar-driven secular evolution picture for their formation. In fact, we show that these nuclear discs have, in the region where they dominate, larger rotational support than the underlying main galaxy disc. In addition, we define a kinematic radius for the nuclear discs and show that it relates to bar radius, ellipticity and strength, and bar-to-total ratio. Comparing our results with photometric studies of galaxy bulges, we find that careful, state-of-the-art galaxy image decompositions are generally able to discern nuclear discs from classical bulges if the images employed have high enough physical spatial resolution. In fact, we show that nuclear discs are typically identified in such image decompositions as photometric bulges with (near-)exponential profiles. However, we find that the presence of composite bulges (galaxies hosting both a classical bulge and a nuclear disc) can often be unnoticed in studies based on photometry alone and suggest a more stringent threshold to the Sérsic index to identify galaxies with pure classical bulges.
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Cavichia, Oscar, Mercedes Mollá, Roberto D. D. Costa, and Walter J. Maciel. "The star formation rate in the inner Milky Way Galaxy." Proceedings of the International Astronomical Union 8, S292 (2012): 98. http://dx.doi.org/10.1017/s1743921313000586.
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AbstractThe present star formation rate (SFR) in the inner Galaxy is puzzling for the chemical evolution models (CEM). No static CEM is able to reproduce the peak of the SFR in the 4 kpc ring. The main reason is probably a shortage of gas, which could be due to the dynamical effects produced by the galactic bar, not considered by these models. We developed a CEM that includes radial gas flows in order to mimic the effects of the galactic bar in the first 5 kpc of the galactic disk. In this model, the star formation (SF) is a two-step process: first, the diffuse gas forms molecular clouds. Then, stars form from cloud-cloud collisions or by the interaction between massive stars and the molecular gas. The former is called spontaneous and the latter induced SF. The mass in the different phases of each region changes by the processes associated with the stellar formation and death by: the SF due to spontaneous fragmentation of gas in the halo; formation of gas clouds in the disk from the diffuse gas; induced SF in the disk due to the interaction between massive stars and gas clouds; and finally, the restitution of the diffuse gas associated to these process of cloud and star formation. In the halo, the star formation rate for the diffuse gas follows a Schmidt law with a power n = 1.5. In the disk, the stars form in two steps: first, molecular clouds are formed from the diffuse gas also following a Schmidt law with n=1.5 and a proportionality factor. Including a specific pattern of radial gas flows, the CEM is able to reproduce with success the peak in the SFR at 4 kpc (fig. 1).
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Nuritdinov, S. N., E. R. Gaynullia, and K. T. Mirtodjieva. "1.17. Bulge and bar: a possible way of their formation." Symposium - International Astronomical Union 184 (1998): 49–50. http://dx.doi.org/10.1017/s0074180900083960.
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Some observational data indicate that galaxy subsystems, including their central areas, first of all are the result of their global nonstationary evolution. That is why we earlier built (Nuritdinov 1992) the exact non-linearly pulsing rotating models of disklike and spherical self-gravitating systems. Unlike other authors we want to research the stability problem of nonlinear nonstationary models. In the present report we want to give only those results of the instability studied, which have a direct attitude to the subject under discussion. We put a certain question: what initial conditions have to exist, for instance, for the value of the virial parameter (2T/|U|)0 and the parameter of anisotropy < Tr > / < T⊥ >, that the collapse of a disk should result in a bar, and the spherical collapse will result in a thick ellipsoidal bulge. To answer the question it is very important to study stability of the solvable nonlinear unequilibrium models. All models discussed below pulsate under the law R = II(ψ)R0, where (Nuritdinov 1985)
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Cuomo, V., J. A. L. Aguerri, E. M. Corsini, and V. P. Debattista. "Relations among structural parameters in barred galaxies with a direct measurement of bar pattern speed." Astronomy & Astrophysics 641 (September 2020): A111. http://dx.doi.org/10.1051/0004-6361/202037945.
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We investigate the relations between the properties of bars and their host galaxies in a sample of 77 nearby barred galaxies, spanning a wide range of morphological types and luminosities, with 34 SB0-SBa and 43 SBab-SBc galaxies. The sample includes all the galaxies with reliable direct measurement of their bar pattern speed based on long-slit or integral-field stellar spectroscopy using the Tremaine-Weinberg method. We limited our analysis to the galaxies with a relatively small relative error on the bar pattern speed (≤50%) and that do not host an ultrafast bar. For each galaxy, we collected the radius, strength, pattern speed, corotation radius, and rotation rate for the bar and we also collected the Hubble type and absolute SDSS r-band magnitude. We also used literature bulge-to-total luminosity ratios for a subsample of 53 galaxies with an available photometric decomposition. We confirmed earlier observational findings that longer bars rotate at lower bar pattern speeds, shorter bars are weaker, and bars with a low rate of bar rotation rotate at faster bar pattern speeds and have smaller corotation radii. In addition, we found that stronger bars rotate at lower bar pattern speeds, as predicted from the interchange of angular momentum during bar evolution, which in turn may depend on different galaxy properties. Moreover, we report that brighter galaxies host longer bars, which rotate at lower bar pattern speeds and have larger corotation radii. This result is in agreement with a scenario of downsizing in bar formation, if more massive galaxies formed earlier and had sufficient time to slow down, grow in length, and push corotation outwards.
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Ansar, Sioree, Sarah Pearson, Robyn E. Sanderson, et al. "Bar Formation and Destruction in the FIRE-2 Simulations." Astrophysical Journal 978, no. 1 (2024): 37. https://doi.org/10.3847/1538-4357/ad8b45.
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Abstract The physical mechanisms responsible for bar formation and destruction in galaxies remain a subject of debate. While we have gained valuable insight into how bars form and evolve from isolated idealized simulations, in the cosmological domain, galactic bars evolve in complex environments, with mergers and gas accretion events occurring in the presence of the turbulent interstellar medium with multiple star formation episodes, in addition to coupling with their host galaxies’ dark matter halos. We investigate the bar formation in 13 Milky Way–mass galaxies from the Feedback in Realistic Environments (FIRE-2) cosmological zoom-in simulations. 8 of the 13 simulated galaxies form bars at some point during their history: three from tidal interactions and five from internal evolution of the disk. The bars in FIRE-2 are generally shorter than the corotation radius (mean bar radius ∼1.53 kpc), have a wide range of pattern speeds (36–97 km s−1 kpc−1), and live for a wide range of dynamical times (2–160 bar rotations). We find that the bar formation in FIRE-2 galaxies is influenced by satellite interactions and the stellar-to-dark-matter mass ratio in the inner galaxy, but neither is a sufficient condition for bar formation. Bar formation is more likely to occur, with the bars formed being stronger and longer-lived, if the disks are kinematically cold; galaxies with high central gas fractions and/or vigorous star formation, on the other hand, tend to form weaker bars. In the case of the FIRE-2 galaxies, these properties combine to produce ellipsoidal bars with strengths A 2/A 0 ∼ 0.1–0.2.
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Weinberg, Martin D. "The Dynamics of the Galactic Bar." International Astronomical Union Colloquium 157 (1996): 516–28. http://dx.doi.org/10.1017/s0252921100050363.
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The dynamics of formation and evolution of structure in barred galaxies is subtle and will require many and detailed observations to discriminate between the alternative hypotheses. Why should someone interested in such problems consider the Milky Way? In terms of data volume, our knowledge of the Milky Way is vast and the availability of detail is its major advantage. In principle, one can study morphological details such as orientations, strengths of asymmetries and kinematics details such as velocity field/pattern speeds using a wide variety of tracers. To illustrate, theorists have not converged on a single mechanism to explain bars (witness the instability vs. secular formation debate). It is possible that both operate in different regimes depending on internal or external influences: internally, triaxialities and misalignments in the bulge, spheroid or halo can apply torques and drive angular momentum waves which saturate to form a bar; and externally, satellite galaxies can exchange orbital angular momentum with its disturbance which has the similar effect. In short, if the Galaxy is indeed barred, it may hold clues to some of the detailed problems posed at this meeting.
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Kumar, Ankit, Mousumi Das, and Sandeep Kumar Kataria. "The effect of dark matter halo shape on bar buckling and boxy/peanut bulges." Monthly Notices of the Royal Astronomical Society 509, no. 1 (2021): 1262–68. http://dx.doi.org/10.1093/mnras/stab3019.
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ABSTRACT It is well established that bars evolve significantly after they form in galaxy discs, often changing shape both in and out of the disc plane. In some cases they may bend or buckle out of the disc plane resulting in the formation of boxy/peanut/x-shape bulges. In this paper we show that the dark matter halo shape affects bar formation and buckling. We have performed N-body simulations of bar buckling in non-spherical dark matter haloes and traced bar evolution for 8 Gyr. We find that bar formation is delayed in oblate haloes, resulting in delayed buckling whereas bars form earlier in prolate haloes leading to earlier buckling. However, the duration of first buckling remains almost comparable. All the models show two buckling events but the most extreme prolate halo exhibits three distinct buckling features. Bars in prolate haloes also show buckling signatures for the longest duration compared to spherical and oblate haloes. Since ongoing buckling events are rarely observed, our study suggests that most barred galaxies may have more oblate or spherical haloes rather than prolate haloes. Our measurement of BPX structures also shows that prolate haloes promote bar thickening and disc heating more than oblate and spherical haloes.
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Li, Zhi, Juntai Shen, Ortwin Gerhard, and Jonathan P. Clarke. "Gas Dynamics in the Galaxy: Total Mass Distribution and the Bar Pattern Speed." Astrophysical Journal 925, no. 1 (2022): 71. http://dx.doi.org/10.3847/1538-4357/ac3823.
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Abstract Gas morphology and kinematics in the Milky Way contain key information for understanding the formation and evolution of our Galaxy. We present hydrodynamical simulations based on realistic barred Milky Way potentials constrained by recent observations. Our model can reproduce most features in the observed longitude–velocity diagram, including the Central Molecular Zone, the Near and Far 3 kpc arms, the Molecular Ring, and the spiral arm tangents. It can also explain the noncircular motions of masers from the recent BeSSeL2 survey. The central gas kinematics are consistent with a mass of 6.9 × 108 M ⊙ in the Nuclear Stellar Disk. Our model predicts the formation of an elliptical gaseous ring surrounding the bar, which is composed of the 3 kpc arms, the Norma arm, and the bar-spiral interfaces. This ring is similar to those “inner” rings in some Milky Way analogs with a boxy/peanut-shaped bulge (e.g., NGC 4565 and NGC 5746). The kinematics of gas near the solar neighborhood are governed by the Local arm. The bar pattern speed constrained by our gas model is 37.5–40 km s−1 kpc−1, corresponding to a corotation radius of R CR = 6.0–6.4 kpc. The rotation curve of our model rises gently within the central ∼ 5 kpc, significantly less steep than those predicted by some recent zoom-in cosmological simulations.
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Pfenniger, Daniel. "Delayed formation of bulges by dynamical processes." Symposium - International Astronomical Union 153 (1993): 387–90. http://dx.doi.org/10.1017/s0074180900123721.
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Two mechanisms involving purely dynamical processes can lead to the formation of a bulge after its disc: 1) small bulges (1 – 2 kpc), including box-shaped bulges and mildly triaxial bulges, can result from the formation and destruction of a bar; 2) big bulges (> 2kpc) à la Sombrero can grow following the accretion of small satellites. Fully consistent N-body simulations show that the fraction of galaxy mass accreted in this way needs to be larger than about 5%. Less accretion does not create smaller bulges, but heats the whole disc. These dynamical effects transforming Hubble types from SB to SA and vice-versa over ≈ 1 – 2 Gyr also indicate, by the secular growth of bulges, a general sense of galactic evolution from Sd to Sa.
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Fragkoudi, F., R. J. J. Grand, R. Pakmor та ін. "Revisiting the tension between fast bars and the ΛCDM paradigm". Astronomy & Astrophysics 650 (червень 2021): L16. http://dx.doi.org/10.1051/0004-6361/202140320.
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The pattern speed with which galactic bars rotate is intimately linked to the amount of dark matter in the inner regions of their host galaxies. In particular, dark matter haloes act to slow down bars via torques exerted through dynamical friction. Observational studies of barred galaxies tend to find that bars rotate fast, while hydrodynamical cosmological simulations of galaxy formation and evolution in the Lambda cold dark matter (ΛCDM) framework have previously found that bars slow down excessively. This has led to a growing tension between fast bars and the ΛCDM cosmological paradigm. In this study we revisit this issue, using the Auriga suite of high-resolution, magneto-hydrodynamical cosmological zoom-in simulations of galaxy formation and evolution in the ΛCDM framework, finding that bars remain fast down to z = 0. In Auriga, bars form in galaxies that have higher stellar-to-dark matter ratios and are more baryon-dominated than in previous cosmological simulations; this suggests that in order for bars to remain fast, massive spiral galaxies must lie above the commonly used abundance matching relation. While this reduces the aforementioned tension between the rotation speed of bars and ΛCDM, it accentuates the recently reported discrepancy between the dynamically inferred stellar-to-dark matter ratios of massive spirals and those inferred from abundance matching. Our results highlight the potential of using bar dynamics to constrain models of galaxy formation and evolution.
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Laurikainen, Eija, Heikki Salo, Ronald Buta, and Johan Knapen. "NIRS0S: Observations of early-type galaxy secular evolution spanning the Sa/S0/disky-E boundaries." Proceedings of the International Astronomical Union 10, H16 (2012): 331. http://dx.doi.org/10.1017/s174392131400595x.
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AbstractNIRS0S (Near-IR S0 galaxy Survey), is a K-band survey of ~ 200 early-type disk galaxies, mainly S0s, 2-3 mag deeper than the 2Micron All Sky Survey. In depth morphological analysis was done, in which multi-component structural decompositions played an important role. Possible implications to internal dynamical galaxy evolution were discussed. S0s were suggested to be former spirals in which star formation has ceased, forming a parallel sequence with spirals (see Fig. 1). If that evolution is faster among the brighter galaxies, the observed magnitude difference between the barred and non-barred S0s could be understood. Bars are suggested to play a critical role in such evolution. For example, the inner lenses in the bright non-barred S0s can be explained as former barlenses (inner parts of bars), in which the elongated bar component has dissolved. We suggest that the last destructive merger event happened at a fairly large redshift.