The quenching and morphological evolution of central galaxies is facilitated by the feedback-driven expulsion of circumgalactic gas. Issue 3 (18th November 2019)

• Record Type: Journal Article
• Authors: Davies, Jonathan J; Crain, Robert A; Oppenheimer, Benjamin D; Schaye, Joop
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 491:Issue 3(2020)
• Page Start: 4462
• Page End: 4480
• Publication Date: 2019-11-18
• Subjects: methods: numerical -- galaxies: evolution -- galaxies: formation -- galaxies: haloes -- quasars: supermassive black holes; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz3201
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We examine the connection between the properties of the circumgalactic medium (CGM) and the quenching and morphological evolution of central galaxies in the EAGLE and IllustrisTNG simulations. The simulations yield very different median CGM mass fractions, f CGM, as a function of halo mass, M 200, with low-mass haloes being significantly more gas-rich in IllustrisTNG than in EAGLE. Nonetheless, in both cases scatter in f CGM at fixed M 200 is strongly correlated with the specific star formation rate and the kinematic morphology of central galaxies. The correlations are strongest for ∼ L ⋆ galaxies, corresponding to the mass scale at which AGN feedback becomes efficient. This feedback elevates the CGM cooling time, preventing gas from accreting on to the galaxy to fuel star formation, and thus establishing a preference for quenched, spheroidal galaxies to be hosted by haloes with low f CGM for their mass. In both simulations, f CGM correlates negatively with the host halo's intrinsic concentration, and hence with its binding energy and formation redshift, primarily because early halo formation fosters the rapid early growth of the central black hole (BH). This leads to a lower f CGM at fixed M 200 in EAGLE because the BH reaches high accretion rates sooner, whilst in IllustrisTNG it occurs because the central BH reaches the mass threshold at which AGN feedback is assumed to switch from thermal to kinetic injection earlier. Despite these differences, there is consensus from these state-of-the-art simulations that the expulsion of efficiently cooling gas from the CGM is a crucial step in the quenching and morphological evolution of central galaxies.