GalICS 2.1: a new semianalytic model for cold accretion, cooling, feedback, and their roles in galaxy formation. Issue 1 (3rd July 2020)

• Record Type: Journal Article
• Authors: Cattaneo, A; Koutsouridou, I; Tollet, E; Devriendt, J; Dubois, Y
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 1(2020)
• Page Start: 279
• Page End: 301
• Publication Date: 2020-07-03
• Subjects: galaxies: evolution -- galaxies: formation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1832
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Dekel & Birnboim 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 Z accr and the shock radius r s . Here, we take their analysis one step further and present a new semianalytic model that computes r s 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 ${\sim }70{{\ \rm per\ cent}}$ of the wind mass is in a cold galactic fountain with a shorter reaccretion time-scale 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 < z < 2.5. Cooling must be mitigated to avoid overpredicting the number density of galaxies with stellar mass $M_{\rm stars}\gt 10^{11}\, {\rm M}_\odot$ but is important to form intermediate-mass galaxies. At $M_{\rm vir}\gt 3\times 10^{11}\, {\rm M}_\odot$, 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 < z < 5.