scholarly journals Velocity dispersion of brightest cluster galaxies in cosmological simulations

2021 ◽  
Vol 507 (4) ◽  
pp. 5780-5795
Author(s):  
I Marini ◽  
S Borgani ◽  
A Saro ◽  
G L Granato ◽  
C Ragone-Figueroa ◽  
...  
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Stellar Envelope ◽  
Cluster Galaxies ◽  
Massive Galaxies ◽  
Brightest Cluster Galaxies ◽  
Stellar Velocity ◽  
Intracluster Light ◽  
The Universe ◽  
Good Agreement

ABSTRACT Using the DIANOGA hydrodynamical zoom-in simulation set of galaxy clusters, we analyse the dynamics traced by stars belonging to the brightest cluster galaxies (BCGs) and their surrounding diffuse component, forming the intracluster light (ICL), and compare it to the dynamics traced by dark matter and galaxies identified in the simulations. We compute scaling relations between the BCG and cluster velocity dispersions and their corresponding masses (i.e. $M_\mathrm{BCG}^{\star }$–$\sigma _\mathrm{BCG}^{\star }$, M200–σ200, $M_\mathrm{BCG}^{\star }$–M200, and $\sigma _\mathrm{BCG}^{\star }$–σ200), we find in general a good agreement with observational results. Our simulations also predict $\sigma _\mathrm{BCG}^{\star }$–σ200 relation to not change significantly up to redshift z = 1, in line with a relatively slow accretion of the BCG stellar mass at late times. We analyse the main features of the velocity dispersion profiles, as traced by stars, dark matter, and galaxies. As a result, we discuss that observed stellar velocity dispersion profiles in the inner cluster regions are in excellent agreement with simulations. We also report that the slopes of the BCG velocity dispersion profile from simulations agree with what is measured in observations, confirming the existence of a robust correlation between the stellar velocity dispersion slope and the cluster velocity dispersion (thus, cluster mass) when the former is computed within 0.1R500. Our results demonstrate that simulations can correctly describe the dynamics of BCGs and their surrounding stellar envelope, as determined by the past star formation and assembly histories of the most massive galaxies of the Universe.

scholarly journals Dynamical masses of brightest cluster galaxies I: stellar velocity anisotropy and mass-to-light ratios

2020 ◽  
Vol 496 (2) ◽  
pp. 1857-1880 ◽  
Author(s):  
S I Loubser ◽  
A Babul ◽  
H Hoekstra ◽  
Y M Bahé ◽  
E O’Sullivan ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Dark Matter Halo ◽  
Cluster Galaxies ◽  
Velocity Anisotropy ◽  
Brightest Cluster Galaxies ◽  
Stellar Velocity ◽  
Total Light ◽  
Intracluster Light

ABSTRACT We investigate the stellar and dynamical mass profiles in the centres of 25 brightest cluster galaxies (BCGs) at redshifts of 0.05 ≤ z ≤ 0.30. Our spectroscopy enables us to robustly measure the Gauss–Hermite higher order velocity moments h3 and h4, which we compare to measurements for massive early-type galaxies, and central group galaxies. We measure positive central values for h4 for all the BCGs. We derive the stellar mass-to-light ratio ($\Upsilon _{\star \rm DYN}$), and velocity anisotropy (β) based on a multi-Gaussian expansion (MGE) and axisymmetric Jeans Anisotropic Methods (cylindrically and spherically aligned). We explicitly include a dark matter halo mass component, which is constrained by weak gravitational lensing measurements for these clusters. We find a strong correlation between anisotropy and velocity dispersion profile slope, with rising velocity dispersion profiles corresponding to tangential anisotropy and decreasing velocity dispersion profiles corresponding to radial anisotropy. The rising velocity dispersion profiles can also indicate a significant contribution from the intracluster light (ICL) to the total light (in projection) in the centre of the galaxy. For a small number of BCGs with rising velocity dispersion profiles, a variable stellar mass-to-light ratio can also account for the profile shape, instead of tangential anisotropy or a significant ICL contribution. We note that, for some BCGs, a variable βz(r) (from radial to tangential anisotropy) can improve the model fit to the observed kinematic profiles. The observed diversity in these properties illustrates that BCGs are not the homogeneous class of objects they are often assumed to be.

scholarly journals Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings

2019 ◽  
Vol 491 (2) ◽  
pp. 2617-2638 ◽  
Author(s):  
Louise O V Edwards ◽  
Matthew Salinas ◽  
Steffanie Stanley ◽  
Priscilla E Holguin West ◽  
Isabella Trierweiler ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Minor Component ◽  
High Signal ◽  
Wide Field ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Galaxy ◽  
Formation And Evolution ◽  
Intracluster Light ◽  
A Minor

ABSTRACT The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $4\, r_{e}$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.

scholarly journals AGN Activity in Brigtest Cluster Galaxies (BCGs)

2019 ◽  
pp. 153-158
Author(s):  
S. Fisek ◽  
S. Alis ◽  
E. K. Ülgen ◽  
F. K. Yelkenci
Keyword(s):  
Galaxy Cluster ◽  
Sloan Digital Sky Survey ◽  
Cluster Galaxies ◽  
Massive Galaxies ◽  
Brightest Cluster Galaxies ◽  
Sky Survey ◽  
Activity Types ◽  
Hα Emission ◽  
Deep Fields ◽  
The Universe

The aim of our study is to classify the Brightest Cluster Galaxies (BCG), which are the brightest and most massive galaxies in the universe and to determine fraction of BCGs showing AGN activity. Within the scope of the study, we combine BCGs from galaxy cluster catalogs which presented by Hao et al. (2010) and Wen et al. (2009) constructed from the SDSS (Sloan Digital Sky Survey) data and BCGs identified from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) Deep fields (Alis, 2009). Our combined sample contains 42490 BCGs. We determine activity types of BCGs by means of BPT diagrams and WISE color-color diagrams. 140 BCGs show AGN activity out of 42490. In addition, we calculated star formation rates (SFR) by using Hα emission lines for 5569 BCGs with suitable spectral data and investigated the correlation between SFR and redshift.

scholarly journals Cosmological evolution of orientations of cluster-sized dark matter haloes and their central galaxies in the Horizon-AGN simulation

2019 ◽  
Author(s):  
Taizo Okabe ◽  
Takahiro Nishimichi ◽  
Masamune Oguri ◽  
Sébastien Peirani ◽  
Tetsu Kitayama ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Cosmic Time ◽  
Triaxial Ellipsoid ◽  
Cluster Galaxies ◽  
Hydrodynamical Simulation ◽  
Brightest Cluster Galaxies ◽  
The Universe ◽  
Three Dimensional Space

Abstract It is known observationally that the major axes of galaxy clusters and their brightest cluster galaxies are roughly aligned with each other. To understand the origin of the alignment, we identify 40 cluster-sized dark matter (DM) haloes with masses higher than 5 × 1013 M⊙ and their central galaxies (CGs) at z ≈ 0 in the Horizon-AGN cosmological hydrodynamical simulation. We trace the progenitors at 50 different epochs between 0 < z < 5. We then fit their shapes and orientations with a triaxial ellipsoid model. While the orientations of both DM haloes and CGs change significantly due to repeated mergers and mass accretions, their relative orientations are well aligned at each epoch even at high redshifts, z > 1. The alignment becomes tighter with cosmic time; the major axes of the CGs and their host DM haloes at present are aligned on average within ∼30○ in the three dimensional space and ∼20○ in the projected plane. The orientations of the major axes of DM haloes on average follow one of the eigen-vectors of the surrounding tidal field that corresponds to the slowest collapsing (or even stretching) mode, and the alignment with the tidal field also becomes tighter. This implies that the orientations of CGs and DM haloes at the present epoch are largely imprinted in the primordial density field of the Universe, whereas strong dynamical interactions such as mergers are important to explain their mutual alignment at each epoch.

scholarly journals The HectoMAP Cluster Survey: Spectroscopically Identified Clusters and their Brightest Cluster Galaxies (BCGs)

2021 ◽  
Vol 923 (2) ◽  
pp. 143
Author(s):  
Jubee Sohn ◽  
Margaret J. Geller ◽  
Ho Seong Hwang ◽  
Antonaldo Diaferio ◽  
Kenneth J. Rines ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Number Density ◽  
Lower Mass ◽  
Strong Concentration ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Redshift Survey ◽  
Minor Mergers ◽  
Reliability Systems ◽  
The Universe

Abstract We apply a friends-of-friends (FoF) algorithm to identify galaxy clusters and we use the catalog to explore the evolutionary synergy between brightest cluster galaxies (BCGs) and their host clusters. We base the cluster catalog on the dense HectoMAP redshift survey (2000 redshifts deg−2). The HectoMAP FoF catalog includes 346 clusters with 10 or more spectroscopic members within the range 0.05 < z < 0.55 and with a median z = 0.29. We list these clusters and their members. We also include central velocity dispersions (σ *,BCG) for the FoF cluster BCGs, a distinctive feature of the HectoMAP FoF catalog. HectoMAP clusters with higher galaxy number density (80 systems) are all genuine clusters with a strong concentration and a prominent BCG in Subaru/Hyper Suprime-Cam images. The phase-space diagrams show the expected elongation along the line of sight. Lower-density systems include some low reliability systems. We establish a connection between BCGs and their host clusters by demonstrating that σ *,BCG /σ cl decreases as a function of cluster velocity dispersion (σ cl), in contrast, numerical simulations predict a constant σ *,BCG/σ cl. Sets of clusters at two different redshifts show that BCG evolution in massive systems is slow over the redshift range z < 0.4. The data strongly suggest that minor mergers may play an important role in BCG evolution in clusters with σ cl ≳ 300 km s−1. For lower mass systems (σ cl < 300 km s−1), major mergers may play a significant role. The coordinated evolution of BCGs and their host clusters provides an interesting test of simulations in high-density regions of the universe.

scholarly journals Intragroup and Intracluster Light

2015 ◽  
Vol 11 (S317) ◽  
pp. 27-34 ◽  
Author(s):  
J. Christopher Mihos
Keyword(s):  
Virgo Cluster ◽  
Nearby Galaxy ◽  
Host Galaxies ◽  
Cluster Galaxies ◽  
Galaxy Groups ◽  
Brightest Cluster Galaxies ◽  
Group Environment ◽  
Tidal Streams ◽  
Intracluster Light ◽  
The Universe

AbstractThe largest stellar halos in the universe are found in massive galaxy clusters, where interactions and mergers of galaxies, along with the cluster tidal field, all act to strip stars from their host galaxies and feed the diffuse intracluster light (ICL) and extended halos of brightest cluster galaxies (BCGs). Studies of the nearby Virgo Cluster reveal a variety of accretion signatures imprinted in the morphology and stellar populations of its ICL. While simulations suggest the ICL should grow with time, attempts to track this evolution across clusters spanning a range of mass and redshift have proved difficult due to a variety of observational and definitional issues. Meanwhile, studies of nearby galaxy groups reveal the earliest stages of ICL formation: the extremely diffuse tidal streams formed during interactions in the group environment.

scholarly journals Brightest cluster galaxies: the centre can(not?) hold

2020 ◽  
Vol 500 (1) ◽  
pp. 310-318
Author(s):  
Roberto De Propris ◽  
Michael J West ◽  
Felipe Andrade-Santos ◽  
Cinthia Ragone-Figueroa ◽  
Elena Rasia ◽  
...  
Keyword(s):  
Dark Matter ◽  
Local Environment ◽  
Major Axis ◽  
Theoretical Models ◽  
Dark Matter Halo ◽  
Gas Distribution ◽  
X Ray ◽  
Cluster Galaxies ◽  
Peculiar Velocities ◽  
Brightest Cluster Galaxies

ABSTRACT We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.

Studying the Patterns of the Universe

2011 ◽  
Vol 20 (2) ◽  
Author(s):  
T. Sepp ◽  
E. Tempel ◽  
M. Gramann ◽  
P. Nurmi ◽  
M. Haupt
Keyword(s):  
Dark Matter ◽  
Galaxy Cluster ◽  
Analytical Models ◽  
Matter Distribution ◽  
Galaxy Groups ◽  
The Galaxy ◽  
Dark Matter Distribution ◽  
Distribution Studies ◽  
The Universe ◽  
Good Agreement

AbstractThe SDSS galaxy catalog is one of the best databases for galaxy distribution studies. The SDSS DR8 data is used to construct the galaxy cluster catalog. We construct the clusters from the calculated luminosity density field and identify denser regions. Around these peak regions we construct galaxy clusters. Another interesting question in cosmology is how observable galaxy structures are connected to underlying dark matter distribution. To study this we compare the SDSS DR7 galaxy group catalog with galaxy groups obtained from the semi-analytical Millennium N-Body simulation. Specifically, we compare the group richness, virial radius, maximum separation and velocity dispersion distributions and find a relatively good agreement between the mock catalog and observations. This strongly supports the idea that the dark matter distribution and galaxies in the semi-analytical models and observations are very closely linked.

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