Nica, A, Oppenheimer, BD, Crain, RA, Bogdán, Á, Davies, JJ, Forman, WR, Kraft, RP and ZuHone, JA (2022) Predictions for the X-ray circumgalactic medium of edge-on discs and spheroids. Monthly Notices of the Royal Astronomical Society, 517 (2). pp. 1958-1969. ISSN 0035-8711

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Abstract

We investigate how the X-ray circumgalactic medium (CGM) of present-day galaxies depends on galaxy morphology and azimuthal angle using mock observations generated from the EAGLE cosmological hydrodynamic simulation. By creating mock stacks of eROSITA-observed galaxies oriented to be edge-on, we make several observationally-testable predictions for galaxies in the stellar mass range M⋆ = 1010.7 − 11.2 M⊙. The soft X-ray CGM of disc galaxies is between 60 and 100% brighter along the semi-major axis compared to the semi-minor axis, between 10-30 kpc. This azimuthal dependence is a consequence of the hot (T > 106 K) CGM being non-spherical: specifically it is flattened along the minor axis such that denser and more luminous gas resides in the disc plane and co-rotates with the galaxy. Outflows enrich and heat the CGM preferentially perpendicular to the disc, but we do not find an observationally-detectable signature along the semi-minor axis. Spheroidal galaxies have hotter CGMs than disc galaxies related to spheroids residing at higher halos masses, which may be measurable through hardness ratios spanning the 0.2 − 1.5 keV band. While spheroids appear to have brighter CGMs than discs for the selected fixed M⋆ bin, this owes to spheroids having higher stellar and halo masses within that M⋆ bin, and obscures the fact that both simulated populations have similar total CGM luminosities at the exact same M⋆. Discs have brighter emission inside 20 kpc and more steeply declining profiles with radius than spheroids. We predict that the eROSITA 4-year all-sky survey should detect many of the signatures we predict here, although targeted follow-up observations of highly inclined nearby discs after the survey may be necessary to observe some of our azimuthally-dependent predictions.

Item Type:	Article
Additional Information:	This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2002 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
SWORD Depositor:	A Symplectic
Date Deposited:	07 Nov 2022 16:19
Last Modified:	07 Nov 2022 16:30
DOI or ID number:	10.1093/mnras/stac2020
URI:	https://researchonline.ljmu.ac.uk/id/eprint/18054

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