Brightest group galaxies-II: the relative contribution of BGGs to the total baryon content of groups at z<1.3

Ghassem Gozaliasl; Alexis Finoguenov; Habib G. Khosroshahi; Bruno M. B. Henriques; Masayuki Tanaka; Olivier Ilbert; Stijn Wuyts; Henry J. McCracken; Francesco Montanari

doi:10.1093/mnras/sty003

paper

Brightest group galaxies-II: the relative contribution of BGGs to the total baryon content of groups at z<1.3

arXiv:1801.01492 · doi:10.1093/mnras/sty003

Abstract

We performed a detailed study of the evolution of the star formation rate (SFR) and stellar mass of the brightest group galaxies (BGGs) and their relative contribution to the total baryon budget within $R_{200}$ ( $f_{b, 200}^{B GG}$ ). The sample comprises 407 BGGs selected from X-ray galaxy groups ( $M_{200} = 1 0^{12.8} - 1 0^{14} M_{⊙}$ ) out to $z \sim 1.3$ identified in the COSMOS, XMM-LSS, and AEGIS fields. We find that BGGs constitute two distinct populations of quiescent and star-forming galaxies and their mean SFR is $\sim 2$ dex higher than the median SFR at $z < 1.3$ . Both the mean and the median SFRs decline with time by $> 2$ dex. The mean (median) of stellar mass of BGGs has grown by $0.3$ dex since $z = 1.3$ to the present day. We show that up to $\sim 45%$ of the stellar mass growth in a star-forming BGG can be due to its star-formation activity. With respect to $f_{b, 200}^{B GG}$ , we find it to increase with decreasing redshift by $\sim 0.35$ dex while decreasing with halo mass in a redshift dependent manner. We show that the slope of the relation between $f_{b, 200}^{B GG}$ and halo mass increases negatively with decreasing redshift. This trend is driven by an insufficient star-formation in BGGs, compared to the halo growth rate. We separately show the BGGs with the 20\% highest $f_{b, 200}^{B GG}$ are generally non-star-forming galaxies and grow in mass by processes not related to star formation (e.g., dry mergers and tidal striping). We present the $M_{⋆} - M_{h}$ and $M_{⋆} / M_{h} - M_{h}$ relations and compare them with semi-analytic model predictions and a number of results from the literature. We quantify the intrinsic scatter in stellar mass of BGGs at fixed halo mass ( $σ_{l o g M_{⋆}}$ ) and find that $σ_{l o g M_{⋆}}$ increases from 0.3 dex at $z \sim 0.2$ to 0.5 dex at $z \sim 1.0$ due to the bimodal distribution of stellar mass.

arXiv commentAccepted for publication in MNRAS, 25 pages, 11 figures

Brightest group galaxies-II: the relative contribution of BGGs to the total baryon content of groups at z<1.3

Abstract

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