Journal articles on the topic 'Galaxies'
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Guhathakurta, P., K. Ing, H. W. Rix, M. Colless, and T. Williams. "Spatially-Resolved Internal Kinematics of 〈z〉 ≈ 0.3 Field Galaxies: Evidence for Rotation." Symposium - International Astronomical Union 171 (1996): 385. http://dx.doi.org/10.1017/s0074180900233044.
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The nature of evolution in faint field galaxies remains a mystery. The Tully-Fisher relation, empirically relating the intrinsic luminosity of a spiral galaxy to its rotation speed, is an important tool for constraining the amount of luminosity evolution in distant field galaxies. Studying the luminosity-vs-linewidth relation for distant galaxies allows one to compare the luminosity of local and distant galaxies. The customary measure of a galaxy's rotation speed is the width of an emission line. It is important, however, to test whether the linewidth is a reliable measure of the galaxy's rotation speed or if it is dominated by turbulent motion within HII regions. In order to do this, we study the spatially-resolved kinematics and distribution of 0[III] gas in about ten 〈B〉∼21 field galaxies at 〈z〉≈0.3.
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Bellovary, Jillian M., Sarra Hayoune, Katheryn Chafla, Donovan Vincent, Alyson Brooks, Charlotte R. Christensen, Ferah D. Munshi, et al. "The origins of off-centre massive black holes in dwarf galaxies." Monthly Notices of the Royal Astronomical Society 505, no. 4 (June 14, 2021): 5129–41. http://dx.doi.org/10.1093/mnras/stab1665.
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ABSTRACT Massive black holes often exist within dwarf galaxies, and both simulations and observations have shown that a substantial fraction of these may be off-centre with respect to their hosts. We trace the evolution of off-centre massive black holes (MBHs) in dwarf galaxies using cosmological hydrodynamical simulations, and show that the reason for off-centre locations is mainly due to galaxy–galaxy mergers. We calculate dynamical time-scales and show that off-centre MBHs are unlikely to sink to their galaxys’ centres within a Hubble time, due to the shape of the hosts’ potential wells and low stellar densities. These wandering MBHs are unlikely to be detected electromagnetically, nor is there a measurable dynamical effect on the galaxy’s stellar population. We conclude that off-centre MBHs may be common in dwarfs, especially if the mass of the MBH is small or the stellar mass of the host galaxy is large. However, detecting them is extremely challenging, because their accretion luminosities are very low and they do not measurably alter the dynamics of their host galaxies.
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Miller, Tim B., and Pieter van Dokkum. "Bayesian Fitting of Multi-Gaussian Expansion Models to Galaxy Images." Astrophysical Journal 923, no. 1 (December 1, 2021): 124. http://dx.doi.org/10.3847/1538-4357/ac2b30.
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Abstract Fitting parameterized models to images of galaxies has become the standard for measuring galaxy morphology. This forward-modeling technique allows one to account for the point-spread function to effectively study semi-resolved galaxies. However, using a specific parameterization for a galaxy’s surface brightness profile can bias measurements if it is not an accurate representation. Furthermore, it can be difficult to assess systematic errors in parameterized profiles. To overcome these issues we employ the Multi-Gaussian expansion (MGE) method of representing a galaxy’s profile together with a Bayesian framework for fitting images. MGE flexibly represents a galaxy’s profile using a series of Gaussians. We introduce a novel Bayesian inference approach that uses pre-rendered Gaussian components, which greatly speeds up computation time and makes it feasible to run the fitting code on large samples of galaxies. We demonstrate our method with a series of validation tests. By injecting galaxies, with properties similar to those observed at z ∼ 1.5, into deep Hubble Space Telescope observations we show that it can accurately recover total fluxes and effective radii of realistic galaxies. Additionally we use degraded images of local galaxies to show that our method can recover realistic galaxy surface brightness and color profiles. Our implementation is available in an open source python package imcascade, which contains all methods needed for the preparation of images, fitting, and analysis of results.
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van Dokkum, Pieter, Zili Shen, Michael A. Keim, Sebastian Trujillo-Gomez, Shany Danieli, Dhruba Dutta Chowdhury, Roberto Abraham, et al. "A trail of dark-matter-free galaxies from a bullet-dwarf collision." Nature 605, no. 7910 (May 18, 2022): 435–39. http://dx.doi.org/10.1038/s41586-022-04665-6.
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AbstractThe ultra-diffuse galaxies DF2 and DF4 in the NGC 1052 group share several unusual properties: they both have large sizes1, rich populations of overluminous and large globular clusters2–6, and very low velocity dispersions that indicate little or no dark matter7–10. It has been suggested that these galaxies were formed in the aftermath of high-velocity collisions of gas-rich galaxies11–13, events that resemble the collision that created the bullet cluster14 but on much smaller scales. The gas separates from the dark matter in the collision and subsequent star formation leads to the formation of one or more dark-matter-free galaxies12. Here we show that the present-day line-of-sight distances and radial velocities of DF2 and DF4 are consistent with their joint formation in the aftermath of a single bullet-dwarf collision, around eight billion years ago. Moreover, we find that DF2 and DF4 are part of an apparent linear substructure of seven to eleven large, low-luminosity objects. We propose that these all originated in the same event, forming a trail of dark-matter-free galaxies that is roughly more than two megaparsecs long and angled 7° ± 2° from the line of sight. We also tentatively identify the highly dark-matter-dominated remnants of the two progenitor galaxies that are expected11 at the leading edges of the trail.
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Ludwig, Eric, Julia Falcone, Mariarosa Marinelli, William Ostling, and Charles T. Liu. "The Relation between Gas-phase Metallicity and Stellar Mass Surface Density in Post-starburst E+A and E+A+ Galaxies within the Coma Cluster Observed by the SDSS-IV MaNGA Survey." Research Notes of the AAS 6, no. 12 (December 8, 2022): 259. http://dx.doi.org/10.3847/2515-5172/aca908.
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Abstract We present an analysis of the Mass–Metallicity Relation (MZR) in 29 post-starburst galaxies in the Coma Cluster. Outward from the central dominant galaxy, NGC 4889, we conducted a conical survey of all galaxies observed by the Sloan Digital Sky Survey Data Release 17 (SDSS DR17) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey within a 5° radius and redshift constraints 0.013 < z < 0.033. We identified 21 E+A galaxies and 8 “E+A+ galaxies” whose spectra matched the criteria of an E+A galaxy, but contain Balmer emission lines, indicating star formation. We utilized the MaNGA data to calculate each galaxy’s star formation rate densities, gas-phase metallicity and stellar mass. We then compared the MZR between E+A galaxies and E+A+ galaxies to observe how varying star formation rates alter this relation.
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Graham, Alister W. "Resequencing the Hubble sequence and the quadratic (black hole mass)–(spheroid stellar mass) relation for elliptical galaxies." Monthly Notices of the Royal Astronomical Society 522, no. 3 (May 2, 2023): 3588–601. http://dx.doi.org/10.1093/mnras/stad1124.
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ABSTRACT One of the most protracted problems in astronomy has been understanding the evolution of galaxy morphology. Much discussion has surrounded how lenticular galaxies may form a bridging population between elliptical and spiral galaxies. However, with recourse to a galaxy’s central black hole mass, accretion-built spiral galaxies have emerged as the bridging population between low-mass lenticular galaxies and the dusty merger-built lenticular galaxies contiguous with elliptical galaxies and ‘brightest cluster galaxies’ in the black hole/galaxy mass diagram. Spiral galaxies, including the Milky Way, appear built from gas accretion and minor mergers onto what were initially lenticular galaxies. These connections are expressed as a new morphology sequence, dubbed the ‘Triangal’, which subsumes elements of the Hubble sequence and the van den Bergh trident and reveals the bridging nature of the often overlooked ellicular galaxies. Furthermore, a quadratic black hole/galaxy mass relation is found to describe ordinary elliptical galaxies. The relation is roughly parallel to the quadratic-like relations observed for the central spheroidal component of spiral galaxies, dust-rich lenticular galaxies, and old dust-poor lenticular galaxies. The brightest cluster galaxies are offset according to expectations from an additional major merger. The findings have implications for feedback from active galactic nuclei, mapping morphology into simulations, and predicting gravitational wave signals from colliding supermassive black holes. A new galaxy speciation model is presented. It disfavours the ‘monolithic collapse’ scenario for spiral, dusty lenticular, and elliptical galaxies. It reveals substantial orbital angular momentum in the Universe’s first galaxies and unites dwarf and ordinary ‘early-type’ galaxies.
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Douglass, Kelly A., and Regina Demina. "Dependence of the Ratio of Total to Visible Mass on Observable Properties of Sloan Digital Sky Survey MaNGA Galaxies." Astrophysical Journal 925, no. 2 (February 1, 2022): 127. http://dx.doi.org/10.3847/1538-4357/ac3b56.
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Abstract Using spectroscopic observations from the Sloan Digital Sky Survey Mapping Nearby Galaxies at Apache Point Observatory Data Release 15, we study the relationships between the ratio of total to visible mass and various parameters characterizing the evolution and environment of the galaxies in this survey. Measuring the rotation curve with the relative velocities of the Hα emission line across a galaxy’s surface, we estimate each galaxy’s total mass. We develop a statistical model to describe the observed distribution in the ratio of total to visible mass, from which we extract the most probable value of this mass ratio for a given sample of galaxies. We present the relationships between the ratio of total to visible mass and several characteristics describing galactic evolution, such as luminosity, gas-phase metallicity, distance to the nearest neighbor, and position on the color–magnitude diagram. We find that faint galaxies with low metallicities, typically in the blue cloud, have the highest ratios of total to visible mass. This mass ratio is significantly reduced when we include the H i mass in the total visible mass, implying that feedback mechanisms are not as strong in low-mass galaxies as previously thought. Those galaxies that exhibit the second-highest ratios of total to visible mass are the brightest with high metallicities, typically members of the red sequence or green valley. Active galactic nucleus activity is likely both the quenching mechanism and the feedback that drives the mass ratio higher in these massive galaxies. Finally, we introduce a parameterization that predicts a galaxy’s ratio of total to visible mass based only on its photometry and luminosity.
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Camps-Fariña, Artemi, Patricia Sánchez-Blázquez, Santi Roca-Fàbrega, and Sebastián F. Sánchez. "Variable metallicity yields as tracers of inflows." Proceedings of the International Astronomical Union 17, S373 (August 2021): 246–48. http://dx.doi.org/10.1017/s1743921322003982.
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AbstractPristine gas accretion is expected to be the main driver of sustained star formation in galaxies. We measure the required amount of accreted gas at each moment over a galaxy’s history to produce the observed metallicity at that time given its star-forming history. More massive galaxies tend to have higher accretion rates and a larger drop of the accretion rate towards the present time. Within the same mass bin galaxies that are currently star-forming or in the Green Valley have similar, sustained, accretion histories while retired galaxies had a steep decline in the past. Plotting the T80 of the individual accretion histories, a measure of how sustained they are, versus the stellar mass and current sSFR we see a distribution such that currently star-forming galaxies have sustained or recent accretion and retired galaxies have declined accretion histories.
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Jeon, Seyoung, Sukyoung K. Yi, Yohan Dubois, Aeree Chung, Julien Devriendt, San Han, Ryan A. Jackson, Taysun Kimm, Christophe Pichon, and Jinsu Rhee. "Star Formation History and Transition Epoch of Cluster Galaxies Based on the Horizon-AGN Simulation." Astrophysical Journal 941, no. 1 (December 1, 2022): 5. http://dx.doi.org/10.3847/1538-4357/ac9d8c.
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Abstract Cluster galaxies exhibit substantially lower star formation rates than field galaxies today, but it is conceivable that clusters were sites of more active star formation in the early universe. Herein, we present an interpretation of the star formation history (SFH) of group/cluster galaxies based on the large-scale cosmological hydrodynamic simulation, Horizon-AGN. We find that massive galaxies in general have small values of e-folding timescales of star formation decay (i.e., “mass quenching”) regardless of their environment, while low-mass galaxies exhibit prominent environmental dependence. In massive host halos (i.e., clusters), the e-folding timescales of low-mass galaxies are further decreased if they reside in such halos for a longer period of time. This “environmental quenching” trend is consistent with the theoretical expectation from ram pressure stripping. Furthermore, we define a “transition epoch” as where cluster galaxies become less star-forming than field galaxies. The transition epoch of group/cluster galaxies varies according to their stellar and host-cluster halo masses. Low-mass galaxies in massive clusters show the earliest transition epoch of ∼7.6 Gyr ago in lookback time. However, this decreases to ∼5.2 Gyr for massive galaxies in low-mass clusters. Based on our findings, we can describe a cluster galaxy’s SFH with regard to the cluster halo-to-stellar mass ratio.
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Magrini, Laura, Mario Perinotto, Romano L. M. Corradi, and Antonio Mampaso. "A Search for Planetary Nebulae in M 33 and M 81." Symposium - International Astronomical Union 209 (2003): 559–60. http://dx.doi.org/10.1017/s0074180900209698.
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We present a study of the PNe systems of two nearby galaxies: the spirals M 33 and M 81. The luminosity functions (PNLFs) for the two PNe systems were built and the distances to both galaxies were given (0.84 ± 0.09 Mpc to M 33 and 3.84 ± 0.41 Mpc to M 81). The behavior of PNe excitation was examined across both galaxies, finding no evidence for substantial differences in excitation between bulge and disk PNe, nor for variations along the galaxian disks.
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Smith, Eric P., and Paul Hintzen. "Multi-Color Imaging of Selected Southern Interacting Galaxies." International Astronomical Union Colloquium 124 (1990): 55–58. http://dx.doi.org/10.1017/s0252921100004887.
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We present preliminary results from a study of selected Arp-Madore Southern Hemisphere peculiar galaxies. Broadband CCD images (BVRI) of a subset of these galaxies allow us to study each galaxy’s optical morphology, color, and (in a crude manner) degree of nuclear activity, and to compare them with similar data we possess on other active galaxies. Many of these galaxies have optical morphologies closely resembling those of powerful radio galaxies (Smith and Heckman 1989), yet their radio emission is unremarkable. Accurate positions for subsequent spectroscopic studies have been determined along with broad band photometry and morphology studies. Detailed observations of these comparatively bright, low-redshift, well-resolved interacting systems should aid our understanding of the role interactions play in triggering galaxy activity. This work is the initial effort in a long term project to study the role played by the dynamics of the interaction in the production and manifestations of activity in galaxies, and the frequency of galaxy mergers.
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Bertola, F., S. Okamura, C. Balkowski, D. Burstein, S. Chakrabarti, P. de Zeeuw, M. Feast, et al. "Commission 28: Galaxies: (Galaxies)." Transactions of the International Astronomical Union 24, no. 1 (2000): 299–310. http://dx.doi.org/10.1017/s0251107x00003230.
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This report covers the period July 1996 to June 1999. It has been prepared by the President of the Commission with contributions from the members of the Organizing Committee and Dr. E.M. Corsini. As discussed in Kyoto and decided by the Organizing Committee, the report is meant to be in the “short” version.
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Okamura, Sadanori. "Commission 28: Galaxies (Galaxies)." Transactions of the International Astronomical Union 25, no. 2 (2007): 171–72. http://dx.doi.org/10.1017/s0251107x00026766.
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Okamura, S., E. Sadler, C. Balkowski, F. Bertola, J. Binney, D. Burstein, P. de Zeeuw, et al. "Commission 28: Galaxies: (Galaxies)." Transactions of the International Astronomical Union 25, no. 1 (2002): 313–16. http://dx.doi.org/10.1017/s0251107x00001620.
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Artale, M. Celeste, Michela Mapelli, Yann Bouffanais, Nicola Giacobbo, Mario Pasquato, and Mario Spera. "Mass and star formation rate of the host galaxies of compact binary mergers across cosmic time." Monthly Notices of the Royal Astronomical Society 491, no. 3 (November 18, 2019): 3419–34. http://dx.doi.org/10.1093/mnras/stz3190.
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ABSTRACT We investigate the properties of the host galaxies of compact binary mergers across cosmic time, by means of population-synthesis simulations combined with galaxy catalogues from the eagle suite. We analyse the merger rate per galaxy of binary neutron stars (BNSs), black hole–neutron star binaries (BHNSs), and binary black holes (BBHs) from redshift zero up to six. The binary merger rate per galaxy strongly correlates with the stellar mass of the host galaxy at any redshift considered here. This correlation is significantly steeper for BNSs than for both BHNSs and BBHs. Moreover, we find that the merger rate per galaxy depends also on host galaxy’s star formation rate (SFR) and metallicity. We derive a robust fitting formula that relates the merger rate per galaxy with galaxy’s SFR, stellar mass, and metallicity at different redshifts. The typical masses of the host galaxies increase significantly as redshift decreases, as a consequence of the interplay between delay time distribution of compact binaries and cosmic assembly of galaxies. Finally, we study the evolution of the merger rate density with redshift. At low redshift (z ≤ 0.1) early-type galaxies give a larger contribution to the merger rate density than late-type galaxies. This trend reverts at z ≥ 1.
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Comerford, Julia M., James Negus, R. Scott Barrows, Dominika Wylezalek, Jenny E. Greene, Francisco Müller-Sánchez, and Rebecca Nevin. "Toward a More Complete Optical Census of Active Galactic Nuclei via Spatially Resolved Spectroscopy." Astrophysical Journal 927, no. 1 (March 1, 2022): 23. http://dx.doi.org/10.3847/1538-4357/ac496a.
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Abstract While emission line flux ratio diagnostics are the most common technique for identifying active galactic nuclei (AGNs) in optical spectra, applying this approach to single-fiber spectra of galaxies can omit entire subpopulations of AGNs. Here, we use spatially resolved spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to construct a sample of 10 galaxies where Baldwin–Philips–Terlevich line flux ratio diagnostics classify each galaxy’s central 3″ spectrum as LINER or star-forming, while >10% of the spaxels in the galaxy’s MaNGA footprint are classified as Seyfert. We obtain Chandra observations of these 10 galaxies with off-nuclear Seyfert regions to determine whether AGNs are actually present in them. Our main result is that 7–10 (depending on strictness of criteria) of the galaxies host one or more X-ray AGNs, even though none of them were classified as AGNs based on their single-fiber optical spectra. We find that these AGNs were not identified in the single-fiber spectra because they are AGNs in the nuclei of companion galaxies, low-luminosity AGNs, dust-obscured AGNs, and/or flickering AGNs. In summary, we find that off-nuclear AGN signatures may increase the number of known AGNs by a factor of two over what conventional single nuclear fiber spectra identify. Our results show that spatially resolved spectroscopy can be leveraged to reveal a more complete census of AGNs that are traditionally missed by single-fiber spectra.
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Correa, Camila A., Joop Schaye, and James W. Trayford. "The origin of the red-sequence galaxy population in the EAGLE simulation." Monthly Notices of the Royal Astronomical Society 484, no. 4 (January 28, 2019): 4401–12. http://dx.doi.org/10.1093/mnras/stz295.
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ABSTRACT We investigate the evolution in colour and morphology of the progenitors of red-sequence galaxies in the EAGLE cosmological hydrodynamical simulation. We quantify colours with u* − r* intrinsic magnitudes and morphologies with a measure of the stellar kinematics. The time when galaxies moved on to the red sequence depends on their morphology. Disc-type galaxies tend to have become red during the last 3 Gyr, while elliptical-type galaxies joined the red sequence earlier, with half the sample already being red 5 Gyr ago. The time-scale, τGreen, of colour transition through the ‘green valley’ depends weakly on the galaxy’s morphological type. Elliptical-type galaxies cross the green valley slightly faster (τGreen ≈ 1 Gyr) than disc-type galaxies (τGreen ≈ 1.5 Gyr). While τGreen is similar for central and satellite galaxies, for satellites τGreen decreases with increasing stellar mass to host-halo mass ratio. Coupled with our finding that galaxies tend to become green after becoming satellites, this indicates that satellite-specific processes are important for quenching red-sequence galaxies. The last time central, elliptical-type red-sequence galaxies left the blue cloud is strongly correlated with the time the luminosity of the central black hole peaked, but this is not the case for discs. This suggests that active galactic nuclei (AGNs) feedback is important for quenching ellipticals, particularly centrals, but not for discs. We find only a weak connection between transformations in colour and morphology.
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Feng, Shuai, Shi-Yin Shen, Fang-Ting Yuan, Y. Sophia Dai, and Karen L. Masters. "The Velocity Map Asymmetry of Ionized Gas in MaNGA. I. The Catalog and General Properties." Astrophysical Journal Supplement Series 262, no. 1 (August 17, 2022): 6. http://dx.doi.org/10.3847/1538-4365/ac80f2.
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Abstract The SDSS-IV MaNGA survey has measured two-dimensional maps of emission-line velocities for a statistically powerful sample of nearby galaxies. The asymmetric features of these kinematics maps reflect the nonrotational component of a galaxy’s internal motion of ionized gas. In this study, we present a catalog of kinematic asymmetry measurements of the Hα velocity map of a sample of 5353 MaNGA galaxies. Based on this catalog, we find that “special” galaxies (e.g., merging galaxies, barred galaxies, and active galactic nucleus host galaxies) contain more galaxies with highly asymmetric velocity maps. However, we notice that more than half of galaxies with high kinematic asymmetry in our sample are quite “regular.” For those “regular” galaxies, kinematic asymmetry shows a significant anticorrelation with stellar mass at log M ⋆ < 9.7 , while such a trend becomes very weak at log M ⋆ > 9.7 . Moreover, at a given stellar mass, the kinematic asymmetry shows weak correlations with photometric morphology, star formation rate, and environment, while it is independent of H i gas content. We also have quantified the observational effects in the kinematic asymmetry measurement. We find that both the signal-to-noise ratio of Hα flux and disk inclination angle contribute to the measures of kinematic asymmetry, while the physical spatial resolution is an irrelevant factor inside the MaNGA redshift coverage.
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Drory, Niv, and David B. Fisher. "A connection between bulge properties and the bimodality of galaxies." Proceedings of the International Astronomical Union 3, S245 (July 2007): 67–70. http://dx.doi.org/10.1017/s1743921308017304.
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AbstractThe global colors and structure of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a “red sequence”, populated prototypically by early-type galaxies, and a “blue cloud”, whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: “classical bulges” that are dynamically hot systems resembling (little) ellipticals, and “pseudobulges”, dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Alas, given the different formation mechanisms of these bulges, the question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio,B/T, or, whether it separates galaxies of different bulge type, irrespective of theirB/T. In this paper, we identify classical bulges and pseudobulges morphologically with HST images in a sample of nearby galaxies. Detailed surface photometry reveals that: (1) The red – blue dichotomy is a function of bulge type: at the sameB/T, pseudobulges are in globally blue galaxies and classical bulges are in globally red galaxies. (2) Bulge type also predicts where the galaxy lies in other (bimodal) global structural parameters: global Sérsic index and central surface brightness. Hence, the red – blue dichotomy is not due to decreasing bulge prominence alone, and the bulge type of a galaxy carries significance for the galaxy's evolutionary history.
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Courteau, Stéphane, and Aaron A. Dutton. "The Mass Distribution in Disk Galaxies." Proceedings of the International Astronomical Union 11, A29B (August 2015): 195–96. http://dx.doi.org/10.1017/s1743921316004865.
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AbstractWe present the relative fraction of baryons and dark matter at various radii in galaxies. For spiral galaxies, this fraction measured in a galaxy's inner parts is typically baryon-dominated (maximal) and dark-matter dominated (sub-maximal) in the outskirts. The transition from maximal to sub-maximal baryons occurs within the inner parts of low-mass disk galaxies (with Vtot ≤ 200 km s−1) and in the outer disk for more massive systems. The mean mass fractions for late- and early-type galaxies vary significantly at the same fiducial radius and circular velocity, suggesting a range of galaxy formation mechanisms. A more detailed discussion, and resolution of the so-called “maximal disk problem”, is presented in Courteau & Dutton, ApJL, 801, 20.
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Hamabata, Akinari, Taira Oogi, Masamune Oguri, Takahiro Nishimichi, and Masahiro Nagashima. "New constraints on red-spiral galaxies from their kinematics in clusters of galaxies." Monthly Notices of the Royal Astronomical Society 488, no. 3 (July 25, 2019): 4117–25. http://dx.doi.org/10.1093/mnras/stz1991.
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ABSTRACTThe distributions of the pairwise line-of-sight velocity between galaxies and their host clusters are segregated according to the galaxy’s colour and morphology. We investigate the velocity distribution of red-spiral galaxies, which represents a rare population within galaxy clusters. We find that the probability distribution function of the pairwise line-of-sight velocity vlos between red-spiral galaxies and galaxy clusters has a dip at vlos = 0, which is a very odd feature, at 93 per cent confidence level. To understand its origin, we construct a model of the phase-space distribution of galaxies surrounding galaxy clusters in three-dimensional space by using cosmological N-body simulations. We adopt a two component model that consists of the infall component, which corresponds to galaxies that are now falling into galaxy clusters, and the splashback component, which corresponds to galaxies that are on their first (or more) orbit after falling into galaxy clusters. We find that we can reproduce the distribution of the line-of-sight velocity of red-spiral galaxies with the dip with a very simple assumption that red-spiral galaxies reside predominantly in the infall component, regardless of the choice of the functional form of their spatial distribution. Our results constrain the quenching time-scale of red-spiral galaxies to a few Gyr, and the radius where the morphological transformation is effective as $r \sim 0.2 \, h^{-1 } \, \rm {Mpc}$.
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Peterken, Thomas, Alfonso Aragón-Salamanca, Michael Merrifield, Vladimir Avila-Reese, Nicholas F. Boardman, Helena Domínguez Sánchez, Dmitry Bizyaev, Niv Drory, Kaike Pan, and Joel R. Brownstein. "Size, shade, or shape? The contribution of galaxies of different types to the star formation history of the Universe from SDSS-IV MaNGA." Monthly Notices of the Royal Astronomical Society 502, no. 3 (February 1, 2021): 3128–43. http://dx.doi.org/10.1093/mnras/stab268.
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ABSTRACT By fitting stellar populations to the fourth generation of the Sloan Digital Sky Survey (SDSS-IV) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey observations of ∼7000 suitably weighted individual galaxies, we reconstruct the star formation history of the Universe, which we find to be in reasonable agreement with previous studies. Dividing the galaxies by their present-day stellar mass, we demonstrate the downsizing phenomenon, whereby the more massive galaxies hosted the most star formation at earlier times. Further dividing the galaxy sample by colour and morphology, we find that a galaxy’s present-day colour tells us more about its historical contribution to the cosmic star formation history than its current morphology. We show that downsizing effects are greatest among galaxies currently in the blue cloud, but that the level of downsizing in galaxies of different morphologies depends quite sensitively on the morphological classification used, due largely to the difficulty in classifying the smaller low-mass galaxies from their ground-based images. Nevertheless, we find agreement that among galaxies with stellar masses $M_{\star } \gt 6\times 10^{9}\, \mathrm{ M}_{\odot }$, downsizing is most significant in spirals. However, there are complicating factors. For example, for more massive galaxies, we find that colour and morphology are predictors of the past star formation over a longer time-scale than in less massive systems. Presumably this effect is reflecting the longer period of evolution required to alter these larger galaxies’ physical properties, but shows that conclusions based on any single property do not tell the full story.
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Kovlakas, K., A. Zezas, J. J. Andrews, A. Basu-Zych, T. Fragos, A. Hornschemeier, B. Lehmer, and A. Ptak. "A census of ultraluminous X-ray sources in the local Universe." Monthly Notices of the Royal Astronomical Society 498, no. 4 (August 17, 2020): 4790–810. http://dx.doi.org/10.1093/mnras/staa2481.
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ABSTRACT Using the Chandra Source Catalog 2.0 and a newly compiled catalogue of galaxies in the local Universe, we deliver a census of ultraluminous X-ray source (ULX) populations in nearby galaxies. We find 629 ULX candidates in 309 galaxies with distance smaller than 40 Mpc. The foreground/background contamination is $\sim \! 20{{\ \rm per\ cent}}$. The ULX populations in bona fide star-forming galaxies scale on average with star formation rate and stellar mass (M⋆) such that the number of ULXs per galaxy is $0.45^{+0.06}_{-0.09}\times \frac{\rm SFR}{\rm M_\odot \, yr^{-1}}{+}3.3^{+3.8}_{-3.2}\times \frac{M_\star }{\rm M_\odot }$. The scaling depends strongly on the morphological type. This analysis shows that early spiral galaxies contain an additional population of ULXs that scales with M⋆. We also confirm the strong anticorrelation of the ULX rate with the host galaxy’s metallicity. In the case of early-type galaxies, we find that there is a non-linear dependence of the number of ULXs with M⋆, which is interpreted as the result of star formation history differences. Taking into account age and metallicity effects, we find that the predictions from X-ray binary population synthesis models are consistent with the observed ULX rates in early-type galaxies, as well as spiral/irregular galaxies.
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Fraser-McKelvie, Amelia, Alfonso Aragón-Salamanca, Michael Merrifield, Karen Masters, Preethi Nair, Eric Emsellem, Katarina Kraljic, et al. "SDSS-IV MaNGA: spatially resolved star formation in barred galaxies." Monthly Notices of the Royal Astronomical Society 495, no. 4 (May 22, 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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Tchernyshyov, Kirill, Jessica K. Werk, Matthew C. Wilde, J. Xavier Prochaska, Todd M. Tripp, Joseph N. Burchett, Rongmon Bordoloi, et al. "The CGM2 Survey: Quenching and the Transformation of the Circumgalactic Medium." Astrophysical Journal 949, no. 2 (May 25, 2023): 41. http://dx.doi.org/10.3847/1538-4357/acc86a.
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Abstract This study addresses how the incidence rate of strong O vi absorbers in a galaxy’s circumgalactic medium (CGM) depends on galaxy mass and, independently, on the amount of star formation in the galaxy. We use Hubble Space Telescope/Cosmic Origins Spectrograph absorption spectroscopy of quasars to measure O vi absorption within 400 projected kpc and 300 km s−1 of 52 galaxies with M * ∼ 3 × 1010 M ⊙. The galaxies have redshifts 0.12 < z < 0.6, stellar masses 1010.1 M ⊙ < M * < 1010.9 M ⊙, and spectroscopic classifications as star-forming or passive. We compare the incidence rates of high column density O vi absorption (N O VI ≥ 1014.3 cm−2) near star-forming and passive galaxies in two narrow ranges of stellar mass and, separately, in a matched range of halo mass. In all three mass ranges, the O vi covering fraction within 150 kpc is higher around star-forming galaxies than around passive galaxies with greater than 3σ-equivalent statistical significance. On average, the CGM of star-forming galaxies with M * ∼ 3 × 1010 M ⊙ contains more O vi than the CGM of passive galaxies with the same mass. This difference is evidence for a CGM transformation that happens together with galaxy quenching and is not driven primarily by halo mass.
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Witherspoon, Catherine A., and Eric M. Wilcots. "Environment of Quiescent Low-mass Galaxies Hosting AGNs in MaNGA." Astrophysical Journal 961, no. 2 (January 25, 2024): 192. http://dx.doi.org/10.3847/1538-4357/acfca8.
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Abstract The discovery of active galactic nuclei (AGNs) in low-mass (M * ≤ 5 × 109 M ⊙) galaxies has pushed forward the idea that AGN feedback may play a role in quenching star formation in the low-mass regime. In order to test whether AGNs can be a dominant quenching mechanism, we must first disentangle the effects of internal and external processes caused by a galaxy’s environment. We have used the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey to produce resolved Baldwin, Phillips, & Terlevich diagrams, and we find 41 AGNs (∼1.3%) in low-mass galaxies. We have studied the group richness (the number of group members) of our AGN and non-AGN samples as a proxy for determining the possible effect of the environment on the gas reservoir in these galaxies. We find that low-mass galaxies hosting AGNs are more likely to be found in isolation or in low-mass groups than galaxies in the non-AGN samples. This preference is even more clear when we split our samples into star-forming and quiescent subsamples. This suggests that environment is not the main cause of quenching in these galaxies, though we cannot rule out the possibility of past mergers.
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Groves, Brent, and Eva Schinnerer. "Dust as a tracer of gas in galaxies." Proceedings of the International Astronomical Union 10, S309 (July 2014): 318. http://dx.doi.org/10.1017/s174392131401014x.
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AbstractWe use a sample of 36 galaxies to study empirical relations between Herschel infrared (IR) luminosities and the total mass of the interstellar gas (H2 + HI). Such a comparison provides a simple empirical relationship without introducing the uncertainty of dust model fitting. We find tight correlations, and provide fits to these relations, between Herschel luminosities and the total gas mass integrated over entire galaxies, with the tightest, almost linear, correlation found for the longest wavelength data (SPIRE500). However, we find that accounting for the gas-phase metallicity (affecting the dust-to-gas ratio) is crucial when applying these relations to low-mass, and presumably high-redshift, galaxies. When examining these relations as a function of galactocentric radius, we find the same correlations, albeit with a larger scatter, up to radius of r ∼ 0.7r25 (containing most of a galaxy's baryonic mass). The tight relations found for the bulk of the galaxy's baryonic content suggest that total gas masses of disk-like (non-merging/ULIRG) galaxies can be inferred from far-infrared continuum measurements in situations where only the latter are available. This work is to appear in Groves et al. (2014).
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Feldmeier-Krause, A., I. Lonoce, and W. L. Freedman. "Stellar Population and Elemental Abundance Gradients of Early-type Galaxies*." Astrophysical Journal 923, no. 1 (December 1, 2021): 65. http://dx.doi.org/10.3847/1538-4357/ac281e.
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Abstract The evolution of galaxies is imprinted on their stellar populations. Several stellar population properties in massive early-type galaxies have been shown to correlate with intrinsic galaxy properties such as the galaxy’s central velocity dispersion, suggesting that stars formed in an initial collapse of gas (z ∼ 2). However, stellar populations change as a function of galaxy radius, and it is not clear how local gradients of individual galaxies are influenced by global galaxy properties and galaxy environment. In this paper, we study the stellar populations of eight early-type galaxies as a function of radius. We use optical spectroscopy (∼4000–8600 Å) and full spectral fitting to measure stellar population age, metallicity, slope of the initial mass function (IMF), and nine elemental abundances (O, Mg, Si, Ca, Ti, C, N, Na, and Fe) out to 1 R e for each galaxy individually. We find a wide range of properties, with ages ranging from 3–13 Gyr. Some galaxies have a radially constant, Salpeter-like IMF, and other galaxies have a super-Salpeter IMF in the center, decreasing to a sub-Salpeter IMF at ∼0.5 R e . We find a global correlation of the central [Z/H] with the central IMF and the radial gradient of the IMF for the eight galaxies, but local correlations of the IMF slope with other stellar population parameters hold only for subsets of the galaxies in our sample. Some elemental abundances also correlate locally with each other within a galaxy, suggesting a common production channel. These local correlations appear only in subsets of our galaxies, indicating variations of the stellar content among different galaxies.
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Yoifoi, Ponlawat, and Wichean Kriwattanawong. "Galaxy evolution in different environments along redshift within the local universe z < 0.8." Journal of Physics: Conference Series 2145, no. 1 (December 1, 2021): 012002. http://dx.doi.org/10.1088/1742-6596/2145/1/012002.
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Abstract This study presents the evolution of the galaxies in different matter density along redshift within the local universe. A sample of 702,352 galaxies was collected from the Sloan Digital Sky Survey (SDSS). Under the limitation of the spectroscopic data, the appropriate photometric redshift was used to represent the spectroscopic redshift in the range of 0.0 ≤ z ≤ 0.8. Number density of galaxies, galaxy’s colors, and star formation activities are considered to describe the evolution of galaxies. In summary, the number density is not clearly different although the Dec and RA of the sky areas are disparate, but it steeply declines along the redshift direction. Considering the number density together with galaxies’ Hα emission line from spectroscopic data, we find that both equivalent of hydrogen alpha and Hα flux tend to decrease along the redshift, similar to the decreasing trend of the number density. Furthermore, the galaxy color trend is found to be redder as a function of the redshift for the magnitude range of -19 ≤ M g ≤ -17. It implies that the overview of the star formation activity of the fainter galaxies at the lower redshift tend to show higher than the ones at higher redshift.
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González Delgado, R. M., E. Pérez, R. Cid Fernandes, R. García-Benito, A. de Amorim, S. F. Sánchez, B. Husemann, et al. "The growth of mass and metallicity in bulges and disks: CALIFA perspective." Proceedings of the International Astronomical Union 10, H16 (August 2012): 338. http://dx.doi.org/10.1017/s1743921314006024.
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AbstractCALIFA (Calar Alto Legacy Integral Field Area) is a 3D spectroscopic survey of 600 nearby galaxies that we are obtaining with PPaK@3.5m at Calar Alto (Sánchez et al. 2012; Husemann et al. 2012). This pioneer survey is providing valuable clues on how the mass and metallicity grow in the different galactic spatial sub-components (“bulge” and “disk”). Processed through spectral synthesis techniques, CALIFA datacubes allow us to, for the first time, spatially resolve the star formation history of galaxies (Cid Fernandes et al. 2012). The richness of this approach is already evident from the results obtained for the first ~ 100 galaxies of the sample (Pérez et al. 2012). We have found that galaxies grow inside-out, and that the growth rate depends on a galaxy's mass. Here, we present the radial variations of physical properties sorting galaxies by their morphological type (Figure 1). We have found a good correlation between the stellar mass surface density, stellar ages and metallicities and the Hubble type, but being the the early type spirals (Sa-Sbc) the galaxies with strong negative age and metallicity gradient from the bulge to the disk.
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Aguerri, J. A. L., M. Girardi, I. Agulli, A. Negri, C. Dalla Vecchia, and L. Domínguez Palmero. "Deep spectroscopy in nearby galaxy clusters – V. The Perseus cluster." Monthly Notices of the Royal Astronomical Society 494, no. 2 (March 24, 2020): 1681–92. http://dx.doi.org/10.1093/mnras/staa800.
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ABSTRACT Dwarfs are the largest population of galaxies in number in the nearby Universe. Deep spectroscopic data are still missing to obtain a better understanding of their formation and evolution processes. This study shows the results obtained from a spectroscopic campaign in the Perseus cluster. We have obtained 963 new galaxy spectra. We have measured the recessional velocity of the galaxies by using a cross-correlation technique. These data have been used to obtain the cluster membership, the dynamics of the galaxies, and the spectroscopic luminosity function (LF) of the cluster. The cluster membership was obtained by using the peak + gap technique, reporting a total of 403 galaxies as cluster members within 1.4r200. The mean velocity and velocity dispersion of the cluster galaxies are Vc = 5258 km s−1 and σc = 1040 km s−1, respectively. We obtained M200 = 1.2 × 1015 M⊙ and r200 = 2.2 Mpc for this cluster. The clusters members were classified blue and red according to their g − r stellar colour. The velocity dispersion of these two families of galaxies is different, indicating that the blue galaxies can be classified as recently accreted into the cluster. We present the spectroscopic galaxy LF of the cluster. This function turned to be flat: α = 0.99 ± 0.06. In addition, blue and red galaxies show similar densities in the faint end of the LF. This indicates that Perseus does not have a population of red dwarf galaxias as large as other nearby clusters. We have compared the LF of the Perseus cluster with other spectroscopic LFs of nearby clusters and those from cosmological simulations. This comparison shows that the spectroscopic LF of nearby galaxy cluster is far from universal.
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Amirkhanian, A. S., A. G. Egikian, H. Tiersch, and D. Stoll. "AGNs in Shakhbazian Compact Groups." International Astronomical Union Colloquium 184 (2002): 87–88. http://dx.doi.org/10.1017/s0252921100030505.
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The results of CCD spectroscopic observations of Shakhbazian compact groups of galaxies (SHCGs) with the 1.54-m (La Silla, Chile), 2.2-m (Calar Alto, Spain) and 2.6-m (Byurakan) telescopes are presented. According to these preliminary data, about 10% of member galaxies in SHCGs are emission-line galaxies (ELGs) including the broad-line AGNs (of classical Seyfert 1 type) and the narrow-emission-line galaxies.A research program has been developed in the University of Potsdam, Potsdam Astrophysikalisches Institut in cooperation with other observatories (particularly with Byurakan Astrophysical Observatory) to perform photometric and spectroscopic investigations of galaxies in the SHCGs. Within the framework of this program the redshift (radial velocity) measurements have been carried out for more than 200 galaxies in 36 SHCGs. The MIDAS software package was used for processing and interpreting of the galaxy spectra. Most of these redshifts were measured for the first time. 180 member galaxies (90%) in these groups have absorption spectra typical of E and SO galaxies. Twenty galaxies (10%) turn out to be ELGs. They are in the range 0.02 ≤ z ≤ 0.17, i.e., the SHCGs lie in approximately the same redshift space as Abell clusters. These compact groups contain predominantly elliptical and lenticular galaxies (del Olmo 1988; Amirkhanian 1989) like the cores of rich, regular, centrally condensed clusters of galaxies. The fraction of spirals falls in the densest matter concentrations. On the other hand, it is a well-established fact that in the local universe the active objects tend to avoid the cores of dense clusters of galaxies (e.g. Green and Yee 1984). That is why the discovery of an emission-line population with broad-line AGNs in SHCGs (Tiersch et al. 1999) was unexpected. As shown by Dressier, Thompson and Shectman (1985) in their sample of 1268 galaxies in the feilds of 14 rich clusters the ELGs comprise 31% of the field galaxies but only 7% of the cluster galaxies. Similarly, according to their statistics AGNs make up 5% of the field sample, but only 1% of the cluster sample. They note that the difference in the distribution of morphological types can only partially explain this effect. Obviously, some sort of environmental influence is present.
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Einasto, Jaan, Mihkel Joeveer, and Enn Saar. "Dark Matter: Observational Aspects." Symposium - International Astronomical Union 117 (1987): 243–61. http://dx.doi.org/10.1017/s0074180900150260.
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A review of observational work on dark matter in USSR is given. Dynamically the dark matter can be located (i) in the galactic disk and/or in dwarf galaxies, (ii) in coronas of galaxies and in clusters of galaxies, and (iii) distributed smoothly in voids. The possible amount of matter in all three forms is discussed. Physically dark matter can be baryonic or non-baryonic, in the latter case either hot, warm or cold. Available information on the nature of dark matter is indirect, coming from theories of the formation of structure in the Universe. Two constraints to the formation scenarios are discussed, the galaxian correlation function and their morphology.
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Delgado, Rosa González, Enrique Pérez, Roberto Cid Fernandes, Rubén García-Benito, André de Amorim, Sebastian F. Sánchez, Bernd Husemann, et al. "CALIFA survey: The spatially resolved star formation history of massive galaxies." Proceedings of the International Astronomical Union 8, S295 (August 2012): 300–303. http://dx.doi.org/10.1017/s1743921313005097.
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AbstractThe Calar Alto Legacy Integral Field Area (CALIFA) project is an ongoing 3D spectroscopic survey of 600 nearby galaxies of all kinds. This pioneer survey is providing valuable clues on how galaxies form and evolve. Processed through spectral synthesis techniques, CALIFA datacubes allow us to, for the first time, spatially resolve the star formation history of galaxies spread across the color-magnitude diagram. The richness of this approach is already evident from the results obtained for the first ~ 1/6 of the sample. Here we show how the different galactic spatial sub-components (“bulge” and “disk”) grow their stellar mass over time. We explore the results stacking galaxies in mass bins, finding that, except at the lowest masses, galaxies grow inside-out, and that the growth rate depends on a galaxy's mass. The growth rate of inner and outer regions differ maximally at intermediate masses. We also find a good correlation between the age radial gradient and the stellar mass density, suggesting that the local density is a main driver of galaxy evolution.
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Remus, Rhea-Silvia, and Duncan A. Forbes. "Accreted or Not Accreted? The Fraction of Accreted Mass in Galaxies from the Magneticum Simulations and Observations." Astrophysical Journal 935, no. 1 (August 1, 2022): 37. http://dx.doi.org/10.3847/1538-4357/ac7b30.
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Abstract In the two-phase scenario of galaxy formation, a galaxy’s stellar mass growth is first dominated by in-situ star formation, and subsequently by accretion. We analyze the radial distribution of the accreted stellar mass in ∼500 galaxies from the (48 Mpc/h)3 box volume of the hydrodynamical cosmological simulation Magneticum, in a stellar-mass range of 1010 to 1012 M ⊙. We find that higher-mass galaxies have larger accreted fractions, as found in previous works, but predict generally higher accretion fractions for low-mass galaxies. Based on the 3D radial distribution of the accreted and in-situ components, we define six galaxy classes, from completely accretion to completely in-situ dominated, and measure the transition radii between in-situ and accretion-dominated regions for galaxies that reveal a transition. About 70% of our galaxies have one transition radius. However, about 10% of the galaxies are accretion dominated everywhere, and about 13% have two transition radii, with the center and the outskirts both being accretion dominated. We show that these classes are strongly correlated with the galaxy merger histories, especially with the cold gas fraction at the time of merging. We find high total in-situ (low accretion) fractions to be associated with smaller, lower-mass galaxies, lower central dark-matter fractions, and larger transition radii. Finally, we show that the dips in observed surface brightness profiles seen in many early-type galaxies do not correspond to the transition from in-situ to accretion-dominated regions, and that any inferred mass fractions are not indicative of the true accreted mass but contain information about the galaxies’ dry-merger history.
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Hunter, Deidre A. "Star Formation in Normal Irregular Galaxies." Symposium - International Astronomical Union 115 (1987): 611–12. http://dx.doi.org/10.1017/s0074180900096492.
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Normal, non-interacting irregular galaxies can be quite successful at forming stars. Therefore, spiral density waves are not necessary to a vigorous production of stars. Nevertheless, there is a large range in star-formation rates among irregular galaxies. Irregulars with common characteristics can have different overall levels of star-formation activity, so that the level of activity does not seem to be simple related to observable global properties of galaxian systems. The constant star formation rates of most normal irregulars also imply the existence of regulatory processes.
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Veilleux, S., J. Bland-Hawthorn, G. Cecil, and P. Shopbell. "9.18. Galactic winds in active galaxies." Symposium - International Astronomical Union 184 (1998): 417–18. http://dx.doi.org/10.1017/s0074180900085454.
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The effects of large-scale galactic winds in active galaxies may be far-reaching. It has been suggested that the Hubble sequence can be understood in terms of a galaxy's greater ability to sustain winds with increasing bulge-to-disk ratio. The large-scale circulation of gas associated with these galactic winds might help explain the mass-metallicity relation between galaxies and the metallicity-radius relation within galaxies. Galactic winds probably contribute non-negligibly to the cosmic X-ray background and may be involved in the quasar absorption-line phenomenon. The cosmological implications of the wind phenomenon have been widely explored in the context of proto-galaxies and quasars. The extremely energetic galactic winds that were likely associated with galaxy formation almost certainly played a key role in heating and ionizing the intergalactic medium at high redshifts and may have created the seeds for the large-scale structure we see today.
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Peterken, Thomas, Michael Merrifield, Alfonso Aragón-Salamanca, Vladimir Avila-Reese, Nicholas F. Boardman, Niv Drory, and Richard R. Lane. "SDSS-IV MaNGA: when is morphology imprinted on galaxies?" Monthly Notices of the Royal Astronomical Society: Letters 500, no. 1 (January 2020): L42—L46. http://dx.doi.org/10.1093/mnrasl/slaa179.
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ABSTRACT It remains an open question as to how long ago the morphology that we see in a present-day galaxy was typically imprinted. Studies of galaxy populations at different redshifts reveal that the balance of morphologies has changed over time, but such snapshots cannot uncover the typical time-scales over which individual galaxies undergo morphological transformation, nor which are the progenitors of today’s galaxies of different types. However, these studies also show a strong link between morphology and star formation rate (SFR) over a large range in redshift, which offers an alternative probe of morphological transformation. We therefore derive the evolution in SFR and stellar mass of a sample of 4342 galaxies in the SDSS-IV MaNGA survey through a stellar population ‘fossil record’ approach, and show that the average evolution of the population shows good agreement with known behaviour from previous studies. Although the correlation between a galaxy’s contemporaneous morphology and SFR is strong over a large range of lookback times, we find that a galaxy’s present-day morphology only correlates with its relatively recent ($\sim \! 2\, \textrm {Gyr}$) star formation history. We therefore find strong evidence that morphological transitions to galaxies’ current appearance occurred on time-scales as short as a few billion years.
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van Dokkum, Pieter. "The Formation & Evolution of Galaxies." Daedalus 143, no. 4 (October 2014): 114–24. http://dx.doi.org/10.1162/daed_a_00311.
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Weighing in at 1042 kilograms and measuring 1021 meters across, galaxies are perhaps the most awe-inspiring objects known to mankind. They are also the only places in an otherwise dark and unforgiving universe where stars and planets are able to form. In the past five to ten years we have made enormous progress in understanding when galaxies came into being and how they changed and evolved over the course of cosmic time. For the first time, we have a rudimentary idea of what our own Milky Way looked like in the distant past, and we can now simulate Milky Way–like galaxies inside powerful computers. As we are starting to understand what happened in our galaxy's past, we are now turning to the question of why it happened. Untangling the complex physical processes that shape galaxies is extremely difficult, and will require continued advances in computers and information from powerful new telescopes coming online in the next decade.
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Sahu, Nandini, Alister Graham, and Benjamin Davis. "The Morphology-dependent Black Hole–Host Galaxy Correlations: A Consequence of Physical Formation Processes." Acta Astrophysica Taurica 3, no. 1 (December 2, 2021): 39–43. http://dx.doi.org/10.31059/aat.vol3.iss1.pp39-43.
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For decades, astronomers have been investigating how the central supermassive black hole (BH) may govern the host galaxy’s properties and vice versa. Our work adds another step to this study. We have performed state-of-theart 2D modeling and multi-component photometric decompositions of the largest-to-date sample of galaxies with dynamically-measured black hole masses (MBH). The multi-component decomposition allows us to accurately extract the bulge (spheroid) stellar luminosity/mass and structural parameters (also for other galaxy components) and provides detailed galaxy morphologies. We investigated the correlations between MBH and various host galaxy properties, including the bulge (M*,sph) and total galaxy (M*,gal) stellar masses discussed here. Importantly, we analyzed the role of galaxy morphology in these correlations. Our work reveals that the BH scaling relations depend on galaxy morphology and thus depend on the galaxy’s formation and evolution physics. Here we discuss that in the MBH–M*,sph diagram, early-type galaxies (ETGs) with a disk, ETGs without a disk, and late-type galaxies (LTG-spirals) define distinct relations, with quadratic slopes but different zero-points. We also review the MBH–M*,gal relation, where ETGs and LTGs define different relations. Notably, the existence of the MBH–M*,gal relations enables one to quickly estimate MBH in other galaxies without going through the multi-component decomposition process to obtain M*,sph. The final morphology-dependent black hole scaling relations provide tests for morphology-aware simulations of galaxies with a central BH and hold insights for BH-galaxy co-evolution theories based on BH accretion and feedback.
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Monachesi, A., E. F. Bell, D. J. Radburn-Smith, B. Harmsen, R. S. de Jong, J. Bailin, B. W. Holwerda, and D. Streich. "Resolving the stellar outskirts of six Milky Way-like galaxies beyond the Local Group." Proceedings of the International Astronomical Union 11, S321 (March 2016): 43. http://dx.doi.org/10.1017/s1743921316008991.
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AbstractModels of galaxy formation in a hierarchical universe predict substantial scatter in the halo-to-halo stellar properties, owing to stochasticity in galaxies’ merger histories. Currently, only few detailed observations of galaxy’s halos are available, mainly for the Milky Way and M31. The Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey is the largest study to date of the resolved stellar populations in the outskirts of disk galaxies and its observations offer a direct test of model predictions. Here we present the results we obtain for six highly inclined nearby Milky Way-mass spiral galaxies. We find a great diversity in the properties of their stellar halos.
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De Looze, Ilse, Jacopo Fritz, and Maarten Baes. "High-resolution, 3D radiative transfer modeling of M51." Proceedings of the International Astronomical Union 10, S309 (July 2014): 310. http://dx.doi.org/10.1017/s1743921314010060.
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AbstractWe present a new technique developed to model the radiative transfer (RT) effects in nearby face-on galaxies. The face-on perspective provides insight into the star-forming regions and clumpy structure, imposing the need for high-resolution 3D models to recover the asymmetric stellar and dust geometries observed in galaxies. RT modeling of the continuum emission of stars and its interaction with the embedding dust in a galaxy's interstellar medium enables a self-consistent study of the main dust heating mechanisms in galaxies. The main advantage of RT calculations is the non-local character of dust heating that can be addressed by tracing the propagation of stellar radiation through the dusty galaxy medium.
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Sattari, Zahra, Bahram Mobasher, Nima Chartab, Daniel D. Kelson, Harry I. Teplitz, Marc Rafelski, Norman A. Grogin, et al. "Fraction of Clumpy Star-forming Galaxies at 0.5 ≤ z ≤ 3 in UVCANDELS: Dependence on Stellar Mass and Environment." Astrophysical Journal 951, no. 2 (July 1, 2023): 147. http://dx.doi.org/10.3847/1538-4357/acd5d6.
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Abstract High-resolution imaging of galaxies in rest-frame UV has revealed the existence of giant star-forming clumps prevalent in high-redshift galaxies. Studying these substructures provides important information about their formation and evolution and informs theoretical galaxy evolution models. We present a new method to identify clumps in galaxies’ high-resolution rest-frame UV images. Using imaging data from CANDELS and UVCANDELS, we identify star-forming clumps in an HST/F160W ≤ 25 AB mag sample of 6767 galaxies at 0.5 ≤ z ≤ 3 in four fields, GOODS-N, GOODS-S, EGS, and COSMOS. We use a low-passband filter in Fourier space to reconstruct the background image of a galaxy and detect small-scale features (clumps) on the background-subtracted image. Clumpy galaxies are defined as those having at least one off-center clump that contributes a minimum of 10% of the galaxy’s total rest-frame UV flux. We measure the fraction of clumpy galaxies (f clumpy) as a function of stellar mass, redshift, and galaxy environment. Our results indicate that f clumpy increases with redshift, reaching ∼65% at z ∼ 1.5. We also find that f clumpy in low-mass galaxies ( 9.5 ≤ log ( M * / M ⊙ ) ≤ 10 ) is 10% higher compared to that of their high-mass counterparts ( log ( M * / M ⊙ ) > 10.5 ). Moreover, we find no evidence of significant environmental dependence of f clumpy for galaxies at the redshift range of this study. Our results suggest that the fragmentation of gas clouds under violent disk instability remains the primary driving mechanism for clump formation, and incidents common in dense environments, such as mergers, are not the dominant processes.
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Yang, Fan, Richard J. Long, Su-Su Shan, Jun-Qiang Ge, Rui Guo, Bo Zhang, Jing-Hua Gao, Xiang Ji, and Ji-Feng Liu. "Galaxy optical variability of Virgo cluster: new tracer for environmental influences on galaxies." Monthly Notices of the Royal Astronomical Society: Letters 496, no. 1 (May 8, 2020): L59—L63. http://dx.doi.org/10.1093/mnrasl/slaa083.
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ABSTRACT We investigate the relationship between the optical variability of galaxies and their distances from the centre of the Virgo cluster using Palomar Transient Factory data. We define the ratio between the standard deviation of the galaxy brightness and the mean value of the standard deviation as a measure of a galaxy’s optical variability. A sample of 814 Virgo galaxies with 230 263 observations shows a monotonically decreasing trend of optical variability with increasing clustercentric distance. The variability level inside the cluster is 3.2σ higher than the level outside. We fit the variability with a linear function and find that the data reject a distance-independent model. We examine 217 background galaxies for comparison and find no significant trend in galaxy variability. We assess the relation with Monte Carlo simulation by rebuilding the brightness of each galaxy. The simulation shows a monotonically decreasing relation for member galaxy variability and a distance-independent relation for background galaxies. Our result is consistent with the theory that the cold gas flowing inwards the cluster centre fuels AGN activity. This work is a new implementation of the method using optical variability to investigate the relation between galaxies evolution and their environment.
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Mukherjee, Sampath, Léon V. E. Koopmans, Crescenzo Tortora, Matthieu Schaller, R. Benton Metcalf, Joop Schaye, and Georgios Vernardos. "SEAGLE – III: Towards resolving the mismatch in the dark-matter fraction in early-type galaxies between simulations and observations." Monthly Notices of the Royal Astronomical Society 509, no. 1 (October 20, 2021): 1245–51. http://dx.doi.org/10.1093/mnras/stab3014.
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ABSTRACT The central dark-matter fraction of galaxies is sensitive to feedback processes during galaxy formation. Strong gravitational lensing has been effective in the precise measurement of the dark-matter fraction inside massive early-type galaxies. Here, we compare the projected dark-matter fraction of early-type galaxies inferred from the SLACS (Sloan Lens ACS Survey) strong-lens survey with those obtained from the Evolution and Assembly of GaLaxies and their Environment (EAGLE), Illustris, and IllustrisTNG hydrodynamical simulations. Previous comparisons with some simulations revealed a large discrepancy, with considerably higher inferred dark-matter fractions – by factors of ≈2–3 – inside half of the effective radius in observed strong-lens galaxies as compared to simulated galaxies. Here, we report good agreement between EAGLE and SLACS for the dark-matter fractions inside both half of the effective radius and the effective radius as a function of the galaxy’s stellar mass, effective radius, and total mass-density slope. However, for IllustrisTNG and Illustris, the dark-matter fractions are lower than observed. This work consistently assumes a Chabrier initial mass function (IMF), which suggests that a different IMF (although not excluded) is not necessary to resolve this mismatch. The differences in the stellar feedback model between EAGLE and Illustris and IllustrisTNG are likely the dominant cause of the difference in their dark-matter fraction and density slope.
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Lotz, Marcel, Rhea-Silvia Remus, Klaus Dolag, Andrea Biviano, and Andreas Burkert. "Gone after one orbit: How cluster environments quench galaxies." Monthly Notices of the Royal Astronomical Society 488, no. 4 (July 30, 2019): 5370–89. http://dx.doi.org/10.1093/mnras/stz2070.
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ABSTRACT The effect of galactic orbits on a galaxy’s internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To understand this connection, we use both the $(0.5 \,$Gpc)3 and the Gpc3 boxes from the cosmological hydrodynamical simulation set Magneticum Pathfinder. We investigate the velocity anisotropy, phase space, and the orbital evolution of up to ∼5 × 105 resolved satellite galaxies within our sample of 6776 clusters with $M_{\mathrm{vir}}\,\, \gt\,\, 10^{14} \, \mathrm{M_{\odot }}$ at low redshift, which we also trace back in time. In agreement with observations, we find that star-forming satellite galaxies inside galaxy clusters are characterized by more radially dominated orbits, independent of cluster mass. Furthermore, the vast majority of star-forming satellite galaxies stop forming stars during their first passage. We find a strong dichotomy both in line-of-sight and radial phase space between star-forming and quiescent galaxies, in line with observations. The tracking of individual orbits shows that the star formation of almost all satellite galaxies drops to zero within $1 \, \mathrm{Gyr}$ after infall. Satellite galaxies that are able to remain star forming longer are characterized by tangential orbits and high stellar mass. All this indicates that in galaxy clusters the dominant quenching mechanism is ram-pressure stripping.
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Franco, M., D. Elbaz, L. Zhou, B. Magnelli, C. Schreiber, L. Ciesla, M. Dickinson, et al. "GOODS-ALMA: The slow downfall of star formation in z = 2–3 massive galaxies." Astronomy & Astrophysics 643 (October 27, 2020): A30. http://dx.doi.org/10.1051/0004-6361/202038312.
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We investigate the properties of a sample of 35 galaxies, detected with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 1.1 mm in the GOODS-ALMA field (area of 69 arcmin2, resolution = 0.60″, rms ≃ 0.18 mJy beam−1). Using the ultraviolet-to-radio deep multiwavelength coverage of the GOODS–South field, we fit the spectral energy distributions of these galaxies to derive their key physical properties. The galaxies detected by ALMA are among the most massive at z = 2−4 (M⋆, med = 8.5 × 1010 M⊙) and they are either starburst or located in the upper part of the galaxy star-forming main sequence. A significant portion of our galaxy population (∼40%), located at z ∼ 2.5 − 3, exhibits abnormally low gas fractions. The sizes of these galaxies, measured with ALMA, are compatible with the trend between the rest-frame 5000 Å size and stellar mass observed for z ∼ 2 elliptical galaxies, suggesting that they are building compact bulges. We show that there is a strong link between star formation surface density (at 1.1 mm) and gas depletion time: The more compact a galaxy’s star-forming region is, the shorter its lifetime will be (without gas replenishment). The identified compact sources associated with relatively short depletion timescales (∼100 Myr) are the ideal candidates to be the progenitors of compact elliptical galaxies at z ∼ 2.
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Boyer, Martha L. "The Impact of AGB Stars on Galaxies." Proceedings of the International Astronomical Union 14, S343 (August 2018): 321–29. http://dx.doi.org/10.1017/s1743921318005707.
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AbstractAt the end of their evolution, asymptotic giant branch (AGB) stars undergo strong pulsation, mass loss, and dust production. Their mass loss results in substantial chemical and dust enrichment of the interstellar medium. Dust evolution models and isotope abundances in presolar grains suggest that AGB stars play a key role in both dust evolution and the star formation process. They are also the brightest stars in galaxies, potentially dominating in the near-infrared. As a result, AGB stars have a significant influence on the evolution and appearance of their host galaxies and thus must be accounted for when interpreting a galaxy’s integrated light. I will highlight new results that describe the impact AGB stars have on galaxies, including how AGB stars are used to probe galaxy evolution.
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Beall, Abigail. "GALAXIES." New Scientist 255, no. 3397 (July 2022): 41–43. http://dx.doi.org/10.1016/s0262-4079(22)01357-4.
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Delfosse, Xavier. "Galaxies." Pour la Science N° 510 - avril, no. 4 (January 4, 2020): 18. http://dx.doi.org/10.3917/pls.510.0018.
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