1,721,000 research outputs found
HeCS-omnibus Clusters - Identification of Brightest Cluster Galaxies
No full textA set of Figure 3 of Sohn et al. (2020, ApJ accepted) showing the BCG identification of the HeCS-omnibus clusters
The Average Stellar Population Age and Metallicity of Intermediate-redshift Quiescent Galaxies
No full textThe HectoMAP spectroscopic survey provides a unique mass-limited sample of more than 35,000 quiescent galaxies (D(n)4000 > 1.5) covering the redshift range 0.2 < z < 0.6. We segregate galaxies in bins of properties based on stellar mass, D(n)4000, and redshift to construct a set of high signal-to-noise spectra representing a massive (M-* > 10(10)M(circle dot)) quiescent population at intermediate redshift. These high-quality summed spectra enable full spectrum fitting and the related extraction of the average stellar population age and metallicity. The average galaxy age increases with the central D(n)4000 as expected. The correlation is essentially invariant with stellar mass; thus, D(n)4000 is a robust proxy for quiescent galaxy stellar population age. HectoMAP provides the first quiescent sample at intermediate redshift comparable with z similar to 0 mass-complete data sets. Scaling relations derived from the HectoMAP summed spectra connect stellar age and metallicity with quiescent galaxy stellar mass up to z similar to 0.5. Anticorrelation between the equivalent width (EW) of the [O ii] emission line and stellar age, together with the mild increase in stellar age with stellar mass, supports a broad range of timescales for the mass assembly of intermediate-redshift quiescent systems. On average, the most massive galaxies (M-* > 10(11)M(circle dot)) assemble the bulk of their stars at earlier epochs. A strong increase in the average stellar metallicity with stellar mass, along with the correlation between the [O ii] EW and metallicity at 0.2 < z < 0.4, suggests that lower mass galaxies are more likely to have experienced recent star formation episodes; related feedback from massive stars affects the chemical enrichment of these galaxies.Y
IllustrisTNG Snapshots for 10 Gyr of Dynamical Evolution of Brightest Cluster Galaxies and Their Host Clusters
Full text linkWe explore the redshift evolution of the dynamical properties of massive
clusters and their brightest cluster galaxies (BCGs) at based on the
IllustrisTNG-300 simulation. We select 270 massive clusters with at and trace their progenitors based on merger
trees. From 67 redshift snapshots covering , we compute the 3D subhalo
velocity dispersion as a cluster velocity dispersion (). We
also calculate the 3D stellar velocity dispersion of the BCGs (). Both and increase as
universe ages. The BCG velocity dispersion grows more slowly than the cluster
velocity dispersion. Furthermore, the redshift evolution of the BCG velocity
dispersion shows dramatic changes at some redshifts resulting from dynamical
interaction with neighboring galaxies (major mergers). We show that
is comparable with at , offering
an interesting observational test. The simulated redshift evolution of
and generally agrees with an observed
cluster sample for , but with large scatter. Future large
spectroscopic surveys reaching to high redshift will test the implications of
the simulations for the mass evolution of both clusters and their BCGs.Comment: 16 pages, 13 figures, 1 table, accepted for publication in The
Astrophysical Journa
Tracing Dark Matter Halos with Satellite Kinematics and the Central Stellar Velocity Dispersion of Galaxies
No full textIt has been suggested that the central stellar velocity dispersion of galaxies can trace dark matter halo mass directly. We test this hypothesis using a complete spectroscopic sample of isolated galaxies surrounded by faint satellite galaxies from the Sloan Digital Sky Survey Data Release 12. We apply a friends-of-friends algorithm with projected linking length Delta D < 100 kpc and radial velocity linking length Delta V < 1000 km s(-1) to construct our sample. Our sample includes 2807 isolated galaxies with 3417 satellite galaxies at 0.01 < z < 0.14. We divide the sample into two groups based on the primary galaxy color: red and blue primary galaxies separated at (g - r)(0) = 0.85. The central stellar velocity dispersions of the primary galaxies are proportional to the luminosities and stellar masses of the same galaxies. Stacking the sample based on the central velocity dispersion of the primary galaxies, we derive the velocity dispersions of their satellite galaxies, which trace the dark matter halo mass of the primary galaxies. The system velocity dispersion of the satellite galaxies shows a remarkably tight correlation with the central velocity dispersion of the primary galaxies for both red and blue samples. In particular, the slope of the relation is identical to 1 for red primary systems. This tight relation suggests that the central stellar velocity dispersion of galaxies is indeed an efficient and robust tracer for dark matter halo mass. We provide empirical relations between the central stellar velocity dispersion and the dark matter halo mass.Y
Velocity Dispersions of Quiescent Galaxies in IllustrisTNG
No full textWe examine the central stellar velocity dispersion of subhalos based on IllustrisTNG cosmological hydrodynamic simulations. The central velocity dispersion is a fundamental observable that links galaxies with their dark matter subhalos. We carefully explore simulated stellar velocity dispersions derived with different definitions to assess possible systematics. We explore the impact of variation in the identification of member stellar particles, the viewing axes, the velocity dispersion computation technique, and simulation resolution. None of these issues impact the velocity dispersion significantly; any systematic uncertainties are smaller than the random error. We examine the stellar mass-velocity dispersion relation as an observational test of the simulations. At fixed stellar mass, the observed velocity dispersions significantly exceed the simulation results. This discrepancy is an interesting benchmark for the IllustrisTNG simulations because the simulations are not explicitly tuned to match this relation. We demonstrate that the stellar velocity dispersion provides measures of the dark matter velocity dispersion and the dark matter subhalo mass.Y
The Coevolution of Massive Quiescent Galaxies and Their Dark Matter Halos over the Last 6 Billion Years
No full textWe investigate the growth of massive quiescent galaxies at z < 0.6 based on the Sloan Digital Sky Survey and the Smithsonian Hectospec Lensing Survey, two magnitude-limited spectroscopic surveys of high data quality and completeness. Our three-parameter model links quiescent galaxies across cosmic time by self-consistently evolving stellar mass, stellar population age-sensitive D(n)4000 index, half-light radius, and stellar velocity dispersion. Stellar velocity dispersion is a robust proxy of dark matter halo mass; we use it to connect galaxies and dark matter halos and thus empirically constrain their coevolution. The typical rate of stellar mass growth is -similar to 10 M-circle dot yr(-1), and dark matter growth rates from our empirical model are remarkably consistent with N-body simulations. Massive quiescent galaxies grow by minor mergers with dark matter halos of mass 10(10)M(circle dot) less than or similar to M-DM less than or similar to 10(12) M-circle dot and evolve parallel to the stellar mass-halo mass (SMHM) relation based on N-body simulations. Thus, the SMHM relation of massive galaxies apparently results primarily from dry minor merging.Y
A Spectroscopic View of the JWST/GTO Strong Lensing Cluster A1489
No full textWe discuss a spectroscopic survey of the strong lensing cluster A1489 that
includes redshifts for 195 cluster members along with central velocity
dispersions for 188 cluster members. The caustic technique applied to the
redshift survey gives the dynamical parameters , Mpc, and a cluster line-of
sight velocity dispersion kms within . These
parameters are very similar to those of other strong lensing systems with
comparably large Einstein radii. We use the spectroscopy and deep photometry to
demonstrate that A1489 is probably dynamically active; its four BCGs have
remarkably different rest frame radial velocities. Like other massive strong
lensing clusters, the velocity dispersion function for members of A1489 shows
an excess for dispersions kms. The central dispersions
also provide enhanced constraints on future lensing models.Comment: 20 pages, 13 figure
Co-evolution of the Brightest Cluster Galaxies and their Host Clusters in IllustrisTNG
No full textWe use the IllustrisTNG simulations to explore the dynamic scaling relation
between massive clusters and their central galaxies (BCGs). The Illustris
TNG300-1 simulation we use includes 280 massive clusters with M enabling a robust statistical analysis. We derive the
line-of-sight velocity dispersion of the stellar particles of the BCGs
(), analogous to the observed BCG stellar velocity dispersion.
We also compute the subhalo velocity dispersion to measure the cluster velocity
dispersion (). Both and are
proportional to the cluster halo mass, but the slopes differ slightly. Thus
like the observed relation, declines as a
function of , but the scatter is large. We explore the redshift
evolution of scaling relation for in a way that can be compared directly with observations. The scaling
relation has a similar slope at high redshift, but the scatter increases
because of the large scatter in . The simulations imply that
high redshift BCGs are dynamically more complex than their low redshift
counterparts.Comment: 12 pages, 12 figures, accepted for publication in the Ap
A Spectroscopic Census of X-Ray Systems in the COSMOS Field
No full textWe investigate spectroscopic properties of galaxy systems identified based on deep X-ray observations in the Cosmic Evolution Survey (COSMOS) field. The COSMOS X-ray system catalog we use includes 180 X-ray systems to a limiting flux of 1.0 x 10(-15) erg cm(-2) s(-1), an order of magnitude deeper than the future e-ROSITA survey. We identify spectroscopic members of these X-ray systems based on the spectroscopic catalog constructed by compiling various spectroscopic surveys including 277 new measurements; 146 X-ray systems are spectroscopically identified groups with more than three spectroscopic members. We identify 2196 spectroscopic redshifts of member candidates in these X-ray systems. The X-ray luminosity (L-x)-velocity dispersion (sigma(v)) scaling relation of the COSMOS X-ray systems is consistent with that of massive X-ray clusters. One of the distinctive features of the COSMOS survey is that it covers the X-ray luminosity range where poor groups overlap the range for extended emission associated with individual quiescent galaxies. We assess the challenges posed by the complex morphology of the distribution of systems with low X-ray luminosity, including groups and individual quiescent galaxies, in the L-x-sigma(v) plane.Y
Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters
No full textWe explore connections between brightest cluster galaxies (BCGs) and their host clusters. We first construct a HeCS-omnibus cluster sample including 227 galaxy clusters within 0.02.<.z.<.0.30; the total number of spectroscopic members from MMT/Hectospec and SDSS observations is 52325. Taking advantage of the large spectroscopic sample, we compute physical properties of the clusters including the dynamical mass and cluster velocity dispersion (scl). We also measure the central stellar velocity dispersion of the BCGs (s*,BCGs) to examine the relation between BCG velocity dispersion and cluster velocity dispersion for the first time. The observed relation between BCG velocity dispersion and the cluster velocity dispersion is remarkably tight. Interestingly, the s*, BCG scl ratio decreases as a function of scl unlike the prediction from the numerical simulation of Dolag et al. The trend in s*, BCG scl suggests that BCG formation is more efficient in lower mass halos.Y
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