Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters

Priyanka Singh; G. M. Voit; Biman B. Nath

doi:10.1093/mnras/staa3827

paper

Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters

arXiv:2008.04917 · doi:10.1093/mnras/staa3827

Abstract

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 ( $M_{500} \sim 1 0^{12.5} - 1 0^{14.5} M_{⊙}$ ). 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 ( $t_{cool} / t_{ff}$ ). 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 $t_{cool} / t_{ff} \sim 50 - 110$ , 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 ( $M_{500} \sim 1 0^{13.5} M_{⊙}$ ) which systematically fall below the model predictions. However, the best fits for $t_{cool} / t_{ff}$ substantially exceed the values typically derived from X-ray observations of individual systems ( $t_{cool} / t_{ff} \sim 10 - 30$ ). 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.

arXiv comment13 pages, 5 figures, 1 table. Accepted for publication in MNRAS

Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters

Abstract

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