Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters

Abstract

We 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 (σ cl ). We also measure the central stellar velocity dispersion of the BCGs (σ * ,BCG s) 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 σ * ,BCG /σ cl ratio decreases as a function of σ cl unlike the prediction from the numerical simulation of Dolag et al. (2010). The trend in σ * ,BCG /σ cl suggests that the BCG formation is more efficient in lower mass halos.

Possible Relations between Brightest Central Galaxies and Their Host Galaxies Clusters and Groups

“…Some star particles are identified which are not bound to any subhalo within the cluster potential. Those star particles are either a diffuse stellar Figure 6 shows that the relation between BCGs σ o and σ cl decreases a function of σ cl which is also consistent with previous result from Sohn et al (2020). They studied the relation between 227 BCGs and their host clusters in the redshift range 0.02 < z < 0.30.…”

“…This type of relations suggests that the most massive groups or clusters host larger central galaxies. On the other hand, the σ 0 /σ cl ratio as a function of σ cl is consistent with Sohn et al (2020).…”

An extreme case of galaxy and cluster co-evolution at z = 0.7

“…Using the pPXF code of Cappellari & Emsellem (2004), we measure the central stellar velocity dispersion of the BCG to be (380 ± 30) km s −1 , well above the average value of 260 km/s for BCGs in the local Universe (Lauer et al 2014) and high for BCGs at any redshift (Sohn et al 2020).…”

The evolution of compact massive quiescent and star-forming galaxies derived from the Re–Rh and Mstar–Mh relations

“…However, at present, current observations provide rather uncertain constraints on at high redshift (see Kawinwanichakij et al 2020 for a detailed discussion of the systematics). In addition, a secure determination of the number density of, especially compact, MGs is hampered by the seizable but still unknown number of optically dark starforming galaxies at high redshift (e.g., Franco et al 2018;Wang et al 2019;Zhou et al 2020;Smail et al 2021). Nevertheless, the results presented in Figure 4 provide clear predictive trends for the evolution of compact and large MGs that, when compared with data from the next generation of observing facilities, will set tight constraints on the quenching mechanisms ( parameter) and on the level of progenitor bias in the size evolution of MGs.…”

“…With the caveat that different definitions of quiescence are adopted in observations, we note that Model 1 is favoured by current data if ≈ 2 − 3. Model 2 might provide a better fit to data if the number density of starforming MGs is underestimated at high redshift (Franco et al 2018;Smail et al 2021).…”