Semi-Analytic Galaxy Evolution (Sage): Model Calibration and Basic Results

Abstract

This paper describes a new publicly available codebase for modeling galaxy formation in a cosmological context, the "Semi-Analytic Galaxy Evolution" model, or SAGE for short.5 SAGE is a significant update to the 2006 model of Croton et al. and has been rebuilt to be modular and customizable. The model will run on any N-body simulation whose trees are organized in a supported format and contain a minimum set of basic halo properties. In this work, we present the baryonic prescriptions implemented in SAGE to describe the formation and evolution of galaxies, and their calibration for three N-body simulations: Millennium, Bolshoi, and GiggleZ. Updated physics include the following: gas accretion, ejection due to feedback, and reincorporation via the galactic fountain; a new gas cooling-radio mode active galactic nucleus (AGN) heating cycle; AGN feedback in the quasar mode; a new treatment of gas in satellite galaxies; and galaxy mergers, disruption, and the build-up of intra-cluster stars. Throughout, we show the results of a common default parameterization on each simulation, with a focus on the local galaxy population.

Dark-ages reionization and galaxy formation simulation – X. The small contribution of quasars to reionization

“…There are more details of the semi-analytic model in Mutch et al (2016). This work extends the current model with a detailed black hole growth prescription based on Croton et al (2016) and is described in the following subsection.…”

“…This suppression is referred to as radio mode feedback. In this case, following 7 Croton et al (2016), ∆m bh,hot is rescaled to be the amount of mass within the cooling radius, ∆m bh,hot = ∆m bh,hot × m cool m heat and the heated mass consequently shrinks to be the cooling mass, m heat =m cool , resulting in a complete quenching of cooling, ∆m cool = −m heat → m cool = 0. Radio mode feedback limits gas condensation in cluster cooling flows and regulates star formation in massive galaxies (Croton et al 2006).…”

“…8 As mergers drive strong gas inflows towards the central region (Capelo et al 2015), cold gas is funnelled to the central black hole of the resulting merged galaxy, significantly increasing its mass. The amount of accretion can be estimated by (Bonoli et al 2009;Croton et al 2016) ∆m bh,max = min…”

“…We adopt the Bondi-Hoyle accretion model proposed in Croton et al (2016) to describe this hot gas accretion. The Bondi-Hoyle accretion rate is given bẏ…”

Physical drivers of galaxies’ cold-gas content: exploring environmental and evolutionary effects with Dark Sage

“…The Dark Sage semi-analytic model ) is a heavily modified version of the models developed by Croton et al (2006Croton et al ( , 2016. Whereas most semi-analytic models evolve the integrated properties of singular baryonic reservoirs, Dark Sage evolves the one-dimensional structure of galactic discs in annuli of fixed specific angular momentum (similar to Stringer & Benson 2007;Dutton & van den Bosch 2009), where j = r vcirc.…”