X-ray Emission From Hot Gas in Galaxy Groups and Clusters in Simba. (arXiv:2003.04115v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Robson_D/0/1/0/all/0/1">Dylan Robson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dave_R/0/1/0/all/0/1">Romeel Davé</a>
We examine X-ray scaling relations for massive halos
($M_{500}>10^{12.3}M_odot$) in the Simba galaxy formation simulation. The
X-ray weighted luminosity, $L_X$ vs. $M_{500}$ has power-law slopes
$approxfrac{5}{3}$ and $approxfrac{8}{3}$ above and below $10^{13.5}
M_{odot}$, 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 $M_{500}>10^{14}M_odot$ halos show a $sim
0.1R_{200}$ core, but at lower masses the profiles are flat at all radii. $T_X$
profiles are flat for $M_{500}<10^{13}M_{odot}$, 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
$S_{rm core}approx200-400$ 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.
We examine X-ray scaling relations for massive halos
($M_{500}>10^{12.3}M_odot$) in the Simba galaxy formation simulation. The
X-ray weighted luminosity, $L_X$ vs. $M_{500}$ has power-law slopes
$approxfrac{5}{3}$ and $approxfrac{8}{3}$ above and below $10^{13.5}
M_{odot}$, 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 $M_{500}>10^{14}M_odot$ halos show a $sim
0.1R_{200}$ core, but at lower masses the profiles are flat at all radii. $T_X$
profiles are flat for $M_{500}<10^{13}M_{odot}$, 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
$S_{rm core}approx200-400$ 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.
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