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.
Reference:
Dylan Robson, Romeel Davé, Redshift Evolution of Galaxy Group X-ray Properties in Simba, arXiv:2107.01206