The resolved and eco g3 initiative: drivers of h i content and x-ray emission in galaxy groups
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Date
2025
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Publisher
Institute of Physics
Abstract
Adding to the RESOLVE and ECO Gas in Galaxy Groups (G3) initiative, we examine possible drivers of group-integrated H i-to-halo mass ratios (MHI,grp/Mhalo) and group X-ray emission, including group halo mass (Mhalo), virialization as probed by crossing time (tcross), presence of active galactic nuclei (AGN), and group-integrated fractional stellar mass growth rate (FSMGRgrp). G3 groups span Mhalo = 1011−1014.5 M⊙ with comprehensive H i gas 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 Mhalo = 1012.6−1014 M⊙ and unambiguously for Mhalo > 1014 M⊙, reflecting an inverse dependence of MHI,grp/Mhalo and hot gas emission on halo mass. At fixed halo mass, MHI,grp/Mhalo transitions to greater spread below tcross ∼ 2 Gyr. Dividing groups across this transition, lower-tcross groups show elevated X-ray emission compared to higher-tcross groups for Mhalo > 1013.3 M⊙, but this trend reverses for Mhalo = 1012.6−1013.3 M⊙. Additionally, AGN-hosting halos below Mhalo ∼ 1012.1 M⊙ exhibit a broad, ∼0.25 dex deep valley in MHI,grp/Mhalo compared to non-AGN-hosting halos with correspondingly reduced FSMGRgrp. When diluted by non-AGN-hosting halos, this valley becomes shallower and narrower, falling roughly between M halo = 10 11.5 M ⊙ and M halo = 10 12.1 M ⊙ in the overall MHI,grp/Mhalo vs. Mhalo relation. We may also detect a second, less easily interpreted valley at Mhalo ∼ 1013 M⊙. Neither valley matches theoretical predictions of a deeper valley located at or above M halo = 10 12.1 M ⊙ .
Description
Keywords
resolved, initiative, x-ray emission, galaxy groups, G3 groups
Citation
Hutchens, Z.L., Kannappan, S.J., Hess, K.M., Baker, A.J., Sun, M., Carr, D.S., Eckert, K.D. and Stark, D.V., 2025. The RESOLVE and ECO G3 Initiative: Drivers of H i Content and X-Ray Emission in Galaxy Groups. The Astrophysical Journal, 985(2), p.228.