The origin of X-ray coronae around simulated disc galaxies

Kelly, Ashley J.; Jenkins, Adrian; Frenk, Carlos S.

Abstract

The existence of hot, accreted gaseous coronae around massive galaxies is a long-standing central prediction of galaxy formation models in the ΛCDM cosmology. While observations now confirm that extraplanar hot gas is present around late-type galaxies, the origin of the gas is uncertain with suggestions that galactic feedback could be the dominant source of energy powering the emission. We investigate the origin and X-ray properties of the hot gas that surrounds galaxies of halo mass, (1011−1014)M⊙⁠, in the cosmological hydrodynamical EAGLE simulations. We find that the central X-ray emission, ≤0.10Rvir, of haloes of mass ≤1013M⊙ originates from gas heated by supernovae (SNe). However, beyond this region, a quasi-hydrostatic, accreted atmosphere dominates the X-ray emission in haloes of mass ≥1012M⊙⁠. We predict that a dependence on halo mass of the hot gas to dark matter mass fraction can significantly change the slope of the LX–Mvir relation (which is typically assumed to be 4/3 for clusters) and we derive the scaling law appropriate to this case. As the gas fraction in haloes increases with halo mass, we find a steeper slope for the LX–Mvir in lower mass haloes, ≤1014M⊙⁠. This varying gas fraction is driven by active galactic nuclei feedback. We also identify the physical origin of the so-called ‘missing feedback’ problem, the apparently low X-ray luminosities observed from high star-forming, low-mass galaxies. This is explained by the ejection of SNe-heated gas from the central regions of the halo.

Citation

Kelly, A. J., Jenkins, A., & Frenk, C. S. (2021). The origin of X-ray coronae around simulated disc galaxies. Monthly Notices of the Royal Astronomical Society, 502(2), 2934-2951. https://doi.org/10.1093/mnras/stab255

• Journal Article Type: Article
• Acceptance Date: Jan 19, 2021
• Online Publication Date: Feb 4, 2021
• Publication Date: 2021-04
• Deposit Date: May 14, 2021
• Publicly Available Date: Jul 15, 2021
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 502
• Issue: 2
• Pages: 2934-2951
• DOI: https://doi.org/10.1093/mnras/stab255
• Public URL: https://durham-repository.worktribe.com/output/1242625