Institute of Astronomy

The role of halo formation history and circumgalactic gas expulsion in the evolution of galaxies

SpeakerTalk DateTalk Series
Rob Crain (LJMU)14 November 2019Institute of Astronomy Colloquia


Modern galaxy formation models posit that the growth of massive galaxies is regulated, and even quenched, by energy liberated as gas accretes onto supermassive black holes (SMBHs) at their centres. I will discuss analyses of cosmological simulations from the EAGLE and IllustrisTNG projects, which adopt differing assumptions about, and implementations of, the coupling of this energy to interstellar gas. The simulations concur that a fundamental (but largely overlooked) step in the quenching process is the ejection of gas from the circumgalactic medium (CGM), the reservoir of diffuse, multiphase gas that envelops galaxies. They also concur that this process is more efficient in early-forming dark matter haloes (at fixed halo mass), despite their gas being more tightly-bound, owing to the earlier growth of the SMBH. However, the differing assumptions yield divergent scaling relations connecting the properties of SMBHs and the CGM, potentially affording an effective route to constrain the influence of SMBHs on the evolution of their host.