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The RESOLVE and ECO G3 Initiative: Drivers of HI Content and X-ray Emission in Galaxy Groups

2025/04/17 by Zackary L. Hutchens, Sheila J. Kannappan, Hutchens, Zackary L. +13
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy group #Galaxy groups and clusters #Halo #Local Group #Milky Way #ROSAT

paper · pdf · doi:10.48550/arxiv.2504.13103

openalex publication_date 2025/04/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

Adding to the RESOLVE and ECO Gas in Galaxy Groups (G3) initiative, we examine possible drivers of group-integrated HI-to-halo mass ratios (M_{\rm HI,grp}/M_{\rm halo}) and group X-ray emission, including group halo mass (M_{\rm halo}), virialization as probed by crossing time (t_{\rm cross}), presence of active galactic nuclei (AGN), and group-integrated fractional stellar mass growth rate (FSMGR_{\rm grp}). G3 groups span M_{\rm halo}=10^11-14.5 M_\odot with comprehensive HI and AGN information, which we combine with X-ray stacking of ROSAT All-Sky data. We detect hot gas emission exceeding AGN and X-ray binary backgrounds confidently for M_{\rm halo}=10^12.6-14 M_\odot and unambiguously for M_{\rm halo}>10¹⁴ M_\odot, reflecting an inverse dependence of M_{\rm HI,grp}/M_{\rm halo} and hot gas emission on halo mass. At fixed halo mass, M_{\rm HI,grp}/M_{\rm halo} transitions to greater spread below t_{\rm cross}∼2 Gyr. Dividing groups across this transition, lower-t_{\rm cross} groups show elevated X-ray emission compared to higher-t_{\rm cross} groups for M_{\rm halo}>10^13.3 M_\odot, but this trend reverses for M_{\rm halo}=10^12.6-13.3 M_\odot. Additionally, AGN-hosting halos below M_{\rm halo}∼10^12.1 M_\odot exhibit a broad, ∼0.25 dex deep valley in M_{\rm HI,grp}/M_{\rm halo} compared to non-AGN-hosting halos with correspondingly reduced FSMGR_{\rm grp}. When diluted by non-AGN-hosting halos, this valley becomes shallower and narrower, falling roughly between M_{\rm halo}=10^11.5 M_\odot and M_{\rm halo}=10^12.1 M_\odot in the overall M_{\rm HI,grp}/M_{\rm halo} vs. M_{\rm halo} relation. We may also detect a second, less easily interpreted valley at M_{\rm halo}∼10¹³ M_\odot. Neither valley matches theoretical predictions of a deeper valley at or above M_{\rm halo}=10^12.1 M_\odot.

The RESOLVE and ECO G3 Initiative: Drivers of HI Content and X-ray Emission in Galaxy Groups

Abstract

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