The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray-line emission

Monthly Notices of the Royal Astronomical Society, vol. 514, pp. 5214–5237

Abstract

ABSTRACT We estimate the detectability of X-ray metal-line emission from the circumgalactic medium (CGM) of galaxies over a large halo mass range ($\, {M}_{{\rm 200c}}=10^{11.5}$–$10^{14.5}\, {\rm M}_{\odot }$), using the EAGLE simulations. With the XRISM Resolve instrument, a few bright (K α or Fe L-shell) lines from $\, {M}_{{\rm 200c}}\gtrsim 10^{13} \, {\rm M}_{\odot }$ haloes should be detectable. Using the Athena X-IFU or the Lynx Main Array, emission lines (especially from O viii and O vii) from the inner CGM of $\, {M}_{{\rm 200c}}\gtrsim 10^{12.5}\, {\rm M}_{\odot }$ haloes become detectable, and intragroup and intracluster gas will be detectable out to the virial radius. With the Lynx Ultra-high Resolution Array, the inner CGM of haloes hosting $\, {L}_{*}$ galaxies is accessible. These estimates do assume long exposure times (∼1 Ms) and large spatial bins (∼1–$10\, \mathrm{arcmin}^{2}$). This emission is dominated by collisionally ionized (CI) gas, and tends to come from halo centres. The emission is biased towards temperatures close to the maximum emissivity temperature for CI gas (Tpeak), and high densities and metallicities. However, for the K α lines, emission can come from hotter gas in haloes where the virialized, volume-filling gas is hotter than Tpeak. Trends of emission with halo mass can largely be explained by differences in virial temperature. Differences in the mass trends of K α, He α-like, and Fe L-shell lines mirror differences in their emissivities as a function of temperature. We conclude that upcoming X-ray missions will open up a new window on to the hot CGM.

Authors 2

1. Nastasha Wijers corresponding Aachen Leiden Observatory

   Leiden University · Northwestern University · Leiden Observatory

   Affiliation as printed

   CIERA and Department of Physics and Astronomy, Northwestern University , 1800 Sherman Ave, Evanston, IL 60201, USA

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands

2. Joop Schaye Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands