X-ray emission from hot gas in galaxy groups and clusters in simba

Abstract

ABSTRACT We examine X-ray scaling relations for massive haloes ($M_{500}\gt 10^{12.3}\, \mathrm{M}_\odot$) in the simba galaxy formation simulation. The X-ray luminosity, LX versus M500 has power-law slopes ${\approx }\frac{5}{3}$ and ${\approx }\frac{8}{3}$ above and below $10^{13.5} \, \mathrm{M}_{\odot }$, deviating from the self-similarity increasingly to low masses. TX − M500 is self-similar above this mass, and slightly shallower below it. Comparing simba to observed TX scalings, we find that LX, LX-weighted [Fe/H], and entropies at 0.1R200 (S0.1) and R500 (S500) all match reasonably well. S500 − TX is consistent with self-similar expectations, but S0.1 − TX is shallower at lower TX, suggesting the dominant form of heating moves from gravitational shocks in the outskirts to non-gravitational feedback in the cores of smaller groups. simba matches observations of LX versus central galaxy stellar mass M*, predicting the additional trend that star-forming galaxies have higher LX(M*). Electron density profiles for $M_{500}\gt 10^{14}\, \mathrm{M}_\odot$ haloes show a ∼0.1R200 core, but the core is larger at lower masses. TX are reasonably matched to observations, but entropy profiles are too flat versus observations for intermediate-mass haloes, with Score ≈ 200–400 keV cm2. simba’s [Fe/H] profile matches observations in the core but overenriches larger radii. We demonstrate that Simba’s bipolar jet AGN feedback is most responsible for increasingly evacuating lower-mass haloes, but the profile comparisons suggest this may be too drastic in the inner regions.