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

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Main Authors: Hutchens, Zackary L., Kannappan, Sheila J., Hess, Kelley M., Baker, Andrew J., Sun, Ming, Carr, Derrick S., Eckert, Kathleen D., Stark, David V.
Format: Preprint
Published: 2025
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author Hutchens, Zackary L.
Kannappan, Sheila J.
Hess, Kelley M.
Baker, Andrew J.
Sun, Ming
Carr, Derrick S.
Eckert, Kathleen D.
Stark, David V.
author_facet Hutchens, Zackary L.
Kannappan, Sheila J.
Hess, Kelley M.
Baker, Andrew J.
Sun, Ming
Carr, Derrick S.
Eckert, Kathleen D.
Stark, David V.
contents 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 $M_{\rm halo}>10^{14}\,M_\odot$, 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 $t_{\rm cross}\sim2$ 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 $M_{\rm halo}\sim10^{12.1}\,M_\odot$ exhibit a broad, $\sim$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 $M_{\rm halo}\sim10^{13}\,M_\odot$. Neither valley matches theoretical predictions of a deeper valley at or above $M_{\rm halo}=10^{12.1}\,M_\odot$.
format Preprint
id arxiv_https___arxiv_org_abs_2504_13103
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The RESOLVE and ECO G3 Initiative: Drivers of HI Content and X-ray Emission in Galaxy Groups
Hutchens, Zackary L.
Kannappan, Sheila J.
Hess, Kelley M.
Baker, Andrew J.
Sun, Ming
Carr, Derrick S.
Eckert, Kathleen D.
Stark, David V.
Astrophysics of Galaxies
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 $M_{\rm halo}>10^{14}\,M_\odot$, 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 $t_{\rm cross}\sim2$ 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 $M_{\rm halo}\sim10^{12.1}\,M_\odot$ exhibit a broad, $\sim$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 $M_{\rm halo}\sim10^{13}\,M_\odot$. Neither valley matches theoretical predictions of a deeper valley at or above $M_{\rm halo}=10^{12.1}\,M_\odot$.
title The RESOLVE and ECO G3 Initiative: Drivers of HI Content and X-ray Emission in Galaxy Groups
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2504.13103