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 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.

Formation Times for Rich Clusters of Galaxies

1977 ◽  
Vol 3 (2) ◽  
pp. 140-142 ◽  
Author(s):  
B. M. Lewis
Keyword(s):  
Gaussian Distribution ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Large Scale Structure ◽  
Elliptical Galaxies ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Number Density ◽  
Radial Gradient ◽  
The Universe

Rich clusters of galaxies are a common feature of the large-scale structure of the Universe. Those studied so far, show striking regularities with (a)a smooth radial gradient of number density.(b)’isothermal’ distributions, which according to Bahcall (1975) have a scatter of only ±15% in the size of their characteristic core radii.(c)their limiting structural diameters are ~50 Mpc (cf. Abell, 1975), if they are identified with superclusters.(d)the magnitude of the velocity dispersion about their centres is generally 600-1000 km s-1, and the velocities are cpnsistent with a gaussian distribution (Yahil and Vidal, 1976; also Faber and Dressier, 1976).(e)The extreme velocities are generally within ±3000 km s-1, and for Coma are ∼2400 km s-1 (Tifft and Gregory, 1976).(f)elliptical galaxies tend to predominate near the centre, spirals in the surrounding loose groups.

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 From 2-D to 3-D by Maximum Entropy Method

1988 ◽  
Vol 130 ◽  
pp. 559-559
Author(s):  
Ofer Lahav ◽  
Donald Lynden-Bell ◽  
Steve F. Gull
Keyword(s):  
Maximum Entropy Method ◽  
Entropy Method ◽  
Number Density ◽  
True Number ◽  
Spread Function ◽  
Redshift Survey ◽  
The Mean ◽  
Image Position ◽  
Distance Indicators ◽  
The Universe

We present a method of estimating distances to clusters of galaxies from twodimensional catalogues. The angular diameters (or magnitudes) of galaxies are used as distance indicators. The mapping from 2-D to 3-D is done by using a ‘diameter function’ (analogous to a luminosity function), which is based on a redshift survey from a section of the sky. The problem is formulated as follows. The number of galaxies with a metric diameter D in a volume element d3r is: where n(r) is the ‘true’ number density of galaxies at position r, n& is the mean number density of galaxies in the universe and ϕ(D)dD is the diameter function. We assume that within a narrow cone n(r) = n(r) and then express N(> θ), the number of galaxies greater than a certain angular diameter θ. In a discrete form we write the relation as: where ni is the density at the i – th distance bin and Pik is our ‘point spread function’, which is a function of the diameter function and Galactic obscuration. We express (2) in terms of χ2 statistics over the measurements, and require it to be less than a certain value. The entropy of the image is expressed as:

scholarly journals Stellar population gradients in brightest cluster galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 316-316
Author(s):  
S. I. Loubser ◽  
P. Sánchez-Blázquez
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Elliptical Galaxies ◽  
Negative Slope ◽  
High Quality ◽  
X Ray ◽  
Cluster Galaxies ◽  
Central Galaxy ◽  
Brightest Cluster Galaxies

AbstractWe present the stellar population and velocity dispersion gradients for a sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which we have obtained high quality long-slit spectra at the Gemini telescopes. With the aim of studying the possible connection between the formation of the BCGs and their host clusters, we explore the relations between the stellar population gradients and properties of the host clusters, as well as the possible connections between the stellar population gradients and other properties of the galaxies. We find mean stellar population gradients (negative Δ[Z/H]/log r gradient of − 0.285 ± 0.064; small positive Δlog(age)/log r gradient of +0.069 ± 0.049; and null Δ[E/Fe]/log r gradient of -0.008 ± 0.032), that are consistent with those of normal massive elliptical galaxies. However, we find a trend between metallicity gradients and velocity dispersion (with a negative slope of − 1.616 ± 0.539), that is not found for the most massive ellipticals. Furthermore, we find trends between the metallicity gradients and K-band luminosities (with a slope of 0.173 ± 0.081) as well as the distance from the BCG to the X-ray peak of the host cluster (with a slope of − 7.546 ± 2.752). The latter indicates a possible relation between the formation of the cluster and that of the central galaxy.

scholarly journals Mass–Velocity Dispersion Relation in MaNGA Brightest Cluster Galaxies

2021 ◽  
Vol 917 (2) ◽  
pp. L24
Author(s):  
Yong Tian ◽  
Han Cheng ◽  
Stacy S. McGaugh ◽  
Chung-Ming Ko ◽  
Yun-Hsin Hsu
Keyword(s):  
Dispersion Relation ◽  
Mass Velocity ◽  
Velocity Dispersion ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies

scholarly journals Luminosity functions of cluster galaxies

2018 ◽  
Vol 618 ◽  
pp. A180 ◽  
Author(s):  
Roberto De Propris ◽  
Malcolm N. Bremer ◽  
Steven Phillipps
Keyword(s):  
Luminosity Function ◽  
Velocity Dispersion ◽  
Lower Mass ◽  
X Ray ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Luminosity Functions ◽  
Blue Galaxies ◽  
Cluster Properties ◽  
Good Agreement

We derive NUV luminosity functions for 6471 NUV detected galaxies in 28 0.02 < z < 0.08 clusters and consider their dependence on cluster properties. We consider optically red and blue galaxies and explore how their NUV LFs vary in several cluster subsamples, selected to best show the influence of environment. Our composite LF is well fit by the Schechter form with M*NUV = −18.98 ± 0.07 and α = −1.87 ± 0.03 in good agreement with values for the Coma centre and the Shapley supercluster, but with a steeper slope and brighter L* than in Virgo. The steep slope is due to the contribution of massive quiescent galaxies that are faint in the NUV. There are significant differences in the NUV LFs for clusters having low and high X-ray luminosities and for sparse and dense clusters, though none are particularly well fitted by the Schechter form, making a physical interpretation of the parameters difficult. When splitting clusters into two subsamples by X-ray luminosity, the ratio of low to high NUV luminosity galaxies is higher in the high X-ray luminosity subsample (i.e., the luminosity function is steeper across the sampled luminosity range). In subsamples split by surface density, when characterised by Schechter functions the dense clusters have an M* about a magnitude fainter than that of the sparse clusters and α is steeper (−1.9 vs. −1.6, respectively). The differences in the data appear to be driven by changes in the LF of blue (star-forming) galaxies. This appears to be related to interactions with the cluster gas. For the blue galaxies alone, the luminosity distributions indicate that for high LX and high velocity dispersion cluster subsamples (i.e., the higher mass clusters), there are relatively fewer high UV luminosity galaxies (or correspondingly a relative excess of low UV luminosity galaxies) in comparison the lower mass cluster subsamples.

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