GalICS 2.1: a new semianalytic model for cold accretion, cooling, feedback, and their roles in galaxy formation

Abstract

<jats:title>Abstract</jats:title> <jats:p>Dekel &amp; Birnboim (2016) proposed that the mass-scale that separates late-type and early-type galaxies is linked to the critical halo mass $M_{\rm vir}^{\rm crit}$ for the propagation of a stable shock and showed that they could reproduce the observed bimodality scale for plausible values of the metallicity of the accreted gas Zaccr and the shock radius rs. Here, we take their analysis one step further and present a new semianalytic model that computes rs from first principles. This advancement allows us to compute $M_{\rm vir}^{\rm crit}$ individually for each halo. Separating cold-mode and hot-mode accretion has little effect on the final galaxy masses if feedback does not preferentially couple to the hot gas. We also present an improved model for stellar feedback where $\sim 70\%$ of the wind mass is in a cold galactic fountain with a shorter reaccretion timescale at high masses. The latter is the key mechanism that allows us to reproduce the low-mass end of the mass function of galaxies over the entire redshift range 0 &amp;lt; z &amp;lt; 2.5. Cooling must be mitigated to avoid overpredicting the number density of galaxies with stellar mass Mstars &amp;gt; 1011 M⊙ but is important to form intermediate-mass galaxies. At Mvir &amp;gt; 3 × 1011 M⊙, cold accretion is more important at high z, where gas is accreted from smaller solid angles, but this is not true at lower masses because high-z filaments have lower metallicities. Our predictions are consistent with the observed metallicity evolution of the intergalactic medium at 0 &amp;lt; z &amp;lt; 5.</jats:p>

Probing the link between quenching and morphological evolution

“…This section describes how GalICS 2.2 follows the hierarchical growth of dark-matter (DM) haloes (Section 2.1), the accretion of gas onto haloes and galaxies (Section 2.2), star formation (Section 2.3), stellar feedback (Section 2.4), disc instabilities (Section 2.5), mergers (Section 2.6), the growth of supermassive BHs (Section 2.7), quenching (Section 2.8) and ram-pressure stripping (Section 2.9). The presentation is more synthetic in Sections 2.1 to 2.4, where the differences with GalICS 2.1 (Cattaneo et al 2020) are small (or inexistent, in Sections 2.1-2.2), and more detailed in Sections 2.5 to 2.9, where the new developments are.…”

“…The virial masses, orbits and merging times of ghost subhaloes, i.e. subhaloes that fall below the resolution limit of the simulation, are computed as in Cattaneo et al (2020).…”

“…( 1) is restored (see Fig. 1 of Cattaneo et al 2020 for the details of how this accretion scheme is implemented).…”

“…Brook et al 2012;Wang et al 2017;Tollet et al 2019), however, suppress gas accretion onto low-mass haloes, so that their baryon fraction is lower than the universal one. We follow Cattaneo et al (2020) and assume that:…”

“…The article starts by presenting the SAM used for this study (Section 2), which we call GalICS 2.2, since it is an updated version of GalICS 2.1 (Cattaneo et al 2020). Gal-ICS 2.2 contains two options for the quenching model: halo quenching (model A) and BH quenching (model B).…”