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Durham University

Department of Physics

Staff profile

Publication details for Mr Tsang Chan

Murray, Norman, Chan, T.K., El-Badry, Kareem, Wetzel, Andrew, Esmerian, Clarke, Kereš, Dušan, Stern, Jonathan, Anglés-Alcázar, Daniel, Faucher-Giguère, Claude-André & Hafen, Zachary (2020). The fates of the circumgalactic medium in the FIRE simulations. Monthly Notices of the Royal Astronomical Society 494(3): 3581-3595.

Author(s) from Durham

Abstract

We analyse the different fates of the circumgalactic medium (CGM) in FIRE-2 cosmological
simulations, focusing on the redshifts z = 0.25 and 2 representative of recent surveys.
Our analysis includes 21 zoom-in simulations covering the halo mass range Mh(z = 0) ∼
1010–1012 M. We analyse both where the gas ends up after first leaving the CGM (its
‘proximate’ fate) and its location at z = 0 (its ‘ultimate’ fate). Of the CGM at z = 2, about
half is found in the ISM or stars of the central galaxy by z = 0 in Mh(z = 2) ∼ 5 × 1011 M
haloes, but most of the CGM in lower mass haloes ends up in the intergalactic medium (IGM).
This is so even though most of the CGM in Mh(z = 2) ∼ 5 × 1010 M haloes first accretes on
to the central galaxy before being ejected into the IGM. On the other hand, most of the CGM
mass at z = 0.25 remains in the CGM by z = 0 at all halo masses analysed. Of the CGM gas
that subsequently accretes on to the central galaxy in the progenitors of Mh(z = 0) ∼ 1012 M
haloes, most of it is cool (T ∼ 104 K) at z = 2 but hot (∼Tvir) at z ∼ 0.25, consistent with the
expected transition from cold mode to hot mode accretion. Despite the transition in accretion
mode, at both z = 0.25 and 2 80 per cent of the cool gas in Mh 1011M haloes will accrete
on to a galaxy. We find that the metallicity of CGM gas is typically a poor predictor of both
its proximate and ultimate fates. This is because there is in general little correlation between
the origin of CGM gas and its fate owing to substantial mixing while in the CGM.