Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters. (arXiv:2008.04917v2 [astro-ph.GA] UPDATED)

Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters. (arXiv:2008.04917v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Singh_P/0/1/0/all/0/1">Priyanka Singh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Voit_G/0/1/0/all/0/1">G. M. Voit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nath_B/0/1/0/all/0/1">Biman B. Nath</a>

We present constraints on a simple analytical model for hot diffuse halo gas,
derived from a fit spanning two orders of magnitude in halo mass ($M_{500} sim
10^{12.5}-10^{14.5} M_{odot}$). The model is motivated by the observed
prevalence of a precipitation limit, and its main free parameter is the central
ratio of gas cooling timescale to free-fall timescale ($t_{rm cool}/t_{rm
ff}$). We use integrated X-ray and thermal Sunyaev-Zel’dovich observations of
the environments around massive galaxies, galaxy groups and clusters, averaged
in halo mass bins, and obtain the best-fitting model parameters. We find
$t_{rm cool}/t_{rm ff} sim 50-110$, depending on the model extrapolation
beyond the halo virial radius and possibly on biases present in the data-sets
used in the fitting analysis. The model adequately describes the entire mass
range, except for intermediate mass halos ($M_{500} sim 10^{13.5} M_{odot}$)
which systematically fall below the model predictions. However, the best fits
for $t_{rm cool}/t_{rm ff}$ substantially exceed the values typically derived
from X-ray observations of individual systems ($t_{rm cool}/t_{rm ff} sim
10-30$). We consider several explanations for those discrepancies, including
X-ray selection biases and a potential anti-correlation between X-ray
luminosity and the central galaxy’s stellar mass.

We present constraints on a simple analytical model for hot diffuse halo gas,
derived from a fit spanning two orders of magnitude in halo mass ($M_{500} sim
10^{12.5}-10^{14.5} M_{odot}$). The model is motivated by the observed
prevalence of a precipitation limit, and its main free parameter is the central
ratio of gas cooling timescale to free-fall timescale ($t_{rm cool}/t_{rm
ff}$). We use integrated X-ray and thermal Sunyaev-Zel’dovich observations of
the environments around massive galaxies, galaxy groups and clusters, averaged
in halo mass bins, and obtain the best-fitting model parameters. We find
$t_{rm cool}/t_{rm ff} sim 50-110$, depending on the model extrapolation
beyond the halo virial radius and possibly on biases present in the data-sets
used in the fitting analysis. The model adequately describes the entire mass
range, except for intermediate mass halos ($M_{500} sim 10^{13.5} M_{odot}$)
which systematically fall below the model predictions. However, the best fits
for $t_{rm cool}/t_{rm ff}$ substantially exceed the values typically derived
from X-ray observations of individual systems ($t_{rm cool}/t_{rm ff} sim
10-30$). We consider several explanations for those discrepancies, including
X-ray selection biases and a potential anti-correlation between X-ray
luminosity and the central galaxy’s stellar mass.

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