A statistical semi-empirical model: satellite galaxies in groups and clusters

Abstract

We present STEEL a STatistical sEmi-Empirical modeL designed to probe the distribution of satellite galaxies in groups and clusters. Our fast statistical methodology relies on tracing the abundances of central and satellite haloes via their mass functions at all cosmic epochs with virtually no limitation on cosmic volume and mass resolution. From mean halo accretion histories and subhalo mass functions the satellite mass function is progressively built in time via abundance matching techniques constrained by number densities of centrals in the local Universe. By enforcing dynamical merging timescales as predicted by high-resolution N-body simulations, we obtain satellite distributions as a function of stellar mass and halo mass consistent with current data. We show that stellar stripping, star formation, and quenching play all a secondary role in setting the number densities of massive satellites above M * 3 × 10 10 M . We further show that observed star formation rates used in our empirical model over predict low-mass satellites below M * 3 × 10 10 M , whereas, star formation rates derived from a continuity equation approach yield the correct abundances similar to previous results for centrals.

Galaxy sizes and the galaxy–halo connection – I. The remarkable tightness of the size distributions

“…Notably, the high mass slope of our SMHM is much steeper than that of Rodríguez-Puebla et al (2017). Our estimate of the SMHM agrees with other studies where an improved photometry was used (Shankar et al 2017, Grylls et al 2019. With a flatter high mass end slope in the SMHM the halo occupation distribution of massive galaxies would be wider (see Sect.…”

ChandraCOSMOS Legacy Survey: Clustering dependence of Type 2 active galactic nuclei on host galaxy properties

“…We assign to each halo: (a) a galaxy stellar mass deduced from the Grylls et al (2019) semi-empirical relation, inclusive of intrinsic (0.15 dex) and measurement scatter (0.2 dex for stellar mass estimates in our COSMOS sample). Satellites are assigned a stellar mass at the redshift of infall; (b) a BH mass assuming empirical BH-galaxy mass relation derived in Shankar et al (2016), inclusive of a stellar mass dependent scatter; (c) an X-ray luminosity following the observationally deduced specific BHAR distribution described by a Schechter function as suggest in Bongiorno et al (2012Bongiorno et al ( , 2016, Aird et al (2016), Georgakakis et al (2017); (d) a SFR following the SFR -stellar mass relation described in Tomczak et al (2016) for main sequence galaxies, including intrinsic (0.2 dex) and measurement (0.2 dex for our COSMOS sample) scatter; (e) an hydrogen column density N H assigned following the Ueda et al (2014) empirical distribution such that AGN can be classified into Type 2 obscured, Type 1 unobscured and Compton Thick AGN; (f) a duty cycle, i.e.…”

“…Figure 6 shows the mean bias as a function of the host galaxy stellar mass and specific BHAR for mock AGN (Equation 10) and for normal galaxies (Equation 9), when Q = 1 and = 2, which corresponds to a fraction of satellite AGN f sat AGN ∼ 0.1 and ∼ 0.15, respectively. The host galaxy stellar masses in the mock catalog are assigned by following Grylls et al (2019), i.e. are defined as Sersic + exponential model (Bernardi et al 2013) with a mass-to-light ratio from Bell et al (2013).…”

Constraining black hole–galaxy scaling relations and radiative efficiency from galaxy clustering

“…The latter relation is inferred from "abundance matching" arguments, i.e., based on number density equivalence between galaxy and host halo number counts 17,18 , n(> M star , z) = n(> M halo , z). We include a scatter of 0.15 dex in stellar mass at fixed host halo mass 17 .…”