X-ray Emission From Hot Gas in Galaxy Groups and Clusters in Simba

Dylan Robson; Romeel Davé

doi:10.1093/mnras/staa2394

paper

X-ray Emission From Hot Gas in Galaxy Groups and Clusters in Simba

arXiv:2003.04115 · doi:10.1093/mnras/staa2394

Abstract

We examine X-ray scaling relations for massive halos ( $M_{500} > 1 0^{12.3} M_{⊙}$ ) in the Simba galaxy formation simulation. The X-ray weighted luminosity, $L_{X}$ vs. $M_{500}$ has power-law slopes $\approx \frac{5}{3}$ and $\approx \frac{8}{3}$ above and below $1 0^{13.5} M_{⊙}$ , deviating from the self-similarity increasingly to low masses. $T_{X} - M_{500}$ is self-similar above this mass, and slightly shallower below it. Comparing Simba to observed $T_{X}$ scalings, we find that $L_{X}$ , $L_{X}$ -weighted [Fe/H], and entropies at $0.1 R_{200}$ ( $S_{0.1}$ ) and $R_{500}$ ( $S_{500}$ ) all match reasonably well. $S_{500} - T_{X}$ is consistent with self-similar expectations, but $S_{0.1} - T_{X}$ is shallower at lower $T_{X}$ , 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 $L_{X}$ versus central galaxy stellar mass $M_{*}$ , predicting the additional trend that star-forming galaxies have higher $L_{X} (M_{*})$ . The electron density profiles for $M_{500} > 1 0^{14} M_{⊙}$ halos show a $\sim 0.1 R_{200}$ core, but at lower masses the profiles are flat at all radii. $T_{X}$ profiles are flat for $M_{500} < 1 0^{13} M_{⊙}$ , and increasingly centrally peaked with mass. The resulting entropy profiles are centrally depressed for the highest and lowest mass halos but flatter for intermediate-mass halos, with $S_{core} \approx 200 - 400$ keV cm $^{2}$ . Simba's [Fe/H] profile matches observations in the core but over-predicts at larger radii, suggesting overly widespread metal distribution. We show that Simba's bipolar jet AGN feedback is most responsible for increasingly evacuating lower-mass halos, thereby suppressing core densities and raising core entropies to improve agreement with X-ray scaling relations.

X-ray Emission From Hot Gas in Galaxy Groups and Clusters in Simba

Abstract

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