Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A267 | |
Number of page(s) | 21 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202449412 | |
Published online | 15 October 2024 |
The hot circumgalactic medium in the eROSITA All-Sky Survey
I. X-ray surface brightness profiles
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
European Southern Observatory, Karl Schwarzschildstrasse 2, 85748 Garching bei München, Germany
4
Department of Astronomy, University of Science and Technology of China, Hefei 230026, China
5
School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
6
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
7
Center for Space Sciences and Technology, University of Maryland, 1000 Hilltop Circle, Baltimore, MD 21250, USA
8
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
Received:
30
January
2024
Accepted:
26
July
2024
Context. The circumgalactic medium (CGM) provides the material needed for galaxy formation and influences galaxy evolution. The hot (T > 106K) CGM is poorly detected around galaxies with stellar masses (M*) lower than 3 × 1011 M⊙ due to the low surface brightness.
Aims. We aim to detect the X-ray emission from the hot CGM around Milky Way-mass (MW-mass, log(M*/M⊙) = 10.5 − 11.0) and M31-mass (log(M*/M⊙) = 11.0 − 11.25) galaxies, in addition to measuring the X-ray surface brightness profile of the hot CGM.
Methods. We applied a stacking technique to gain enough statistics to detect the hot CGM. We used the X-ray data from the first four SRG/eROSITA All-Sky Surveys (eRASS:4). We discussed how the satellite galaxies could bias the stacking and the method we used to carefully build the central galaxy samples. Based on the SDSS spectroscopic survey and halo-based group finder algorithm, we selected central galaxies with spectroscopic redshifts of zspec < 0.2 and stellar masses of 10.0 < log(M*/M⊙) < 11.5 (85 222 galaxies) – or halo masses of 11.5 < log(M200m/M⊙) < 14.0 (125,512 galaxies). By stacking the X-ray emission around galaxies, we obtained the mean X-ray surface brightness profiles. We masked the detected X-ray point sources and carefully modeled the X-ray emission from the unresolved active galactic nuclei (AGN) and X-ray binaries (XRB) to obtain the X-ray emission from the hot CGM.
Results. We measured the X-ray surface brightness profiles for central galaxies of log(M*/M⊙) > 10.0 or log(M200m/M⊙) > 11.5. We detected the X-ray emission around MW-mass and more massive central galaxies extending up to the virial radius (Rvir). The signal-to-noise ratio (S/N) of the extended emission around MW-mass (M31-mass) galaxy is about 3.1σ (4.7σ) within Rvir. We used a β model to describe the X-ray surface brightness profile of the hot CGM (SX, CGM). We obtained a central surface brightness of log(SX,0[erg s−1 kpc−2]) = 36.7−0.4+1.4 (37.1−0.4+1.5) and β = 0.43−0.06+0.10 (0.37−0.02+0.04) for MW-mass (M31-mass) galaxies. For galaxies with log(M200m/M⊙) > 12.5, the extended X-ray emission is detected with S/N > 2.8σ and the SX, CGM can be described by a β model with β ≈ 0.4 and log(SX,0[erg s−1 kpc−2]) > 37.2. We estimated the baryon budget of the hot CGM and obtained a value that is lower than the prediction of ΛCDM cosmology, indicating significant gas depletion in these halos. We extrapolated the hot CGM profile measured within Rvir to larger radii and found that within ≈3Rvir, the baryon budget is close to the ΛCDM cosmology prediction.
Conclusions. We measured the extended X-ray emission from representative populations of central galaxies around and above MW-mass out to Rvir. Our results set a firm footing for the presence of the hot CGM around such galaxies. These measurements constitute a new benchmark for galaxy evolution models and possible implementations of feedback processes therein.
Key words: galaxies: general / galaxies: halos / galaxies: statistics / X-rays: galaxies
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model.
Open Access funding provided by Max Planck Society.
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