The hot circumgalactic medium in the eROSITA All-Sky Survey

II. Scaling relations between X-ray luminosity and galaxies’ mass

¹ Max-Planck-Institut für extraterrestrische Physik (MPE), Gießenbachstraße 1, 85748 Garching bei München, Germany
² INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
³ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴ Center for Space Sciences and Technology, University of Maryland, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ European Southern Observatory, Karl Schwarzschildstrasse 2, 85748 Garching bei München, Germany
⁷ Department of Astronomy, University of Science and Technology of China, Hefei 230026, China
⁸ School of Astronomy and Space Science, University of Science and Technology of China Hefei 230026, China

Received: 30 January 2024
Accepted: 23 June 2024

Abstract

Aims. Understanding how the properties of galaxies relate to the properties of the hot circum-galactic medium (CGM) around them can constrain galaxy evolution models. We aim to measure the scaling relations between the X-ray luminosity of the hot CGM and the fundamental properties (stellar mass and halo mass) of a galaxy.

Methods. We measured the X-ray luminosity of the hot CGM based on the surface brightness profiles of central galaxy samples measured from Spectrum Roentgen Gamma (SRG)/eROSITA all-sky survey data. We related the X-ray luminosity to the galaxies’ stellar and halo mass, and we compared the observed relations to the self-similar model and intrinsic (i.e., not forward-modeled) output of the IllustrisTNG, EAGLE, and SIMBA simulations.

Results. The average hot CGM X-ray luminosity (L_X, CGM) correlates with the galaxy’s stellar mass (M_*). It increases from (1.6 ± 2.1) × 10³⁹ erg s⁻¹ to (3.4 ± 0.3) × 10⁴¹ erg s⁻¹, when log(M_*) increases from 10.0 to 11.5. A power law describes the correlation as log(L_X, CGM) = (2.4 ± 0.1)×log(M_*)+(14.6 ± 1.5). The hot CGM X-ray luminosity as a function of halo mass is measured within log(M_500c) = 11.3 − 13.7, extending our knowledge of the scaling relation by more than two orders of magnitude. L_X, CGM increases with M_500c from (3.0 ± 1.6) × 10³⁹ erg s⁻¹ at log(M_500c) = 11.3 to (1.3 ± 0.1) × 10⁴² erg s⁻¹ at log(M_500c) = 13.7. The relation follows a power law of log(L_X, CGM) = (1.32 ± 0.05)×log(M_500c)+(24.1 ± 0.7). Our observations highlight the necessity of non-gravitational processes at the galaxy group scale while suggesting these processes are sub-dominant at the galaxy scale. We show that the outputs of current cosmological galaxy simulations generally align with the observational results uncovered here but with possibly important deviations in selected mass ranges.

Conclusions. We explore, at the low mass end, the average scaling relations between the CGM X-ray luminosity and the galaxy’s stellar mass or halo mass, which constitutes a new benchmark for galaxy evolution models and feedback processes.