Redshift Evolution of Galaxy Group X-ray Properties in Simba

We examine the evolution of intragroup gas X-ray scaling relations for group-sized halos (M500=1012.3−15M⊙) in the Simba galaxy formation simulation. X-ray luminosity LX vs M500 shows increasing deviation from self-similarity from z=3→0, with M500<1013.5M⊙ halos exhibiting a large reduction in LXand slight increase in X-ray luminosity-weighted temperature TX. These shifts are driven by a strong drop in fgas with time for these halos, and coincides with the onset of black hole jet feedback in these systems at z∼1.5 in Simba. The connection with black hole feedback is corroborated by fBH≡MBH/M500in M500<1013.5M⊙ halos being strongly anti-correlated with LX and fgas at $z\la 1.5$. This is further reflected in the scatter of LX−TX: halos with small fBH lie near self-similarity, while those with the highest fBH lie furthest below. Turning off jet feedback results in mostly self-similar behaviour down to z=0. For the X-ray weighted metallicity ZX, stellar feedback impacts the enrichment of halo gas. Finally, halo profiles show that jet feedback flattens the electron density and entropy profiles, and introduces a core in X-ray surface brightness particularly at M500<1013.5M⊙. This argues that intragroup X-ray evolution is largely driven by jet feedback removing hot gas from the cores of massive groups, and expelling gas altogether in less massive groups.

Dylan RobsonRomeel Davé, Redshift Evolution of Galaxy Group X-ray Properties in Simba, arXiv:2107.01206