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Astro Seminar

The coupled roles of halo assembly history, black hole growth and circumgalactic gas expulsion in governing galaxy evolution.

Speaker: Robert Crain (LJMU)
Date: Wednesday 23 November 2022
Time: 14:00
Venue: N3.28/Zoom

I will present results from several suites of cosmological hydrodynamical simulations, which indicate that the evolution of simulated present-day ~L* central galaxies is markedly influenced by the assembly history of their parent dark matter halo. In particular, galaxies hosted by early-forming haloes have preferentially lower specific star formation rates (often even being quenched), and less disky morphologies, than counterparts with late-forming haloes. The simulation show that early halo formation fosters the growth of more-massive central black holes (compared to late-forming haloes of similar present-day dynamical mass), and the extra feedback energy liberated by their growth depletes the circumgalactic medium of the efficiently cooling gas that would otherwise replenish interstellar gas consumed by star formation. A central prediction of this scenario is that the circumgalactic medium of quenched ~L* galaxies is of a lower density than that of star-forming counterparts, for which recent analyses of eROSITA X-ray data lend enticing support. I will also briefly show how controlled simulations, starting from 'genetically modified' initial conditions, enable the influence of halo assembly history on galaxy evolution to be disentangled from large-scale environment effects.