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ABSTRACT This paper presents a newly established sample of 19 unique galaxies and galaxy groups at redshift z = 0.89–1.21 in six QSO fields from the Cosmic Ultraviolet Baryon Survey (CUBS), designated as the CUBSz1 sample. In this sample, nine galaxies or galaxy groups show absorption features, while the other 10 systems exhibit 2σ upper limits of $$\log N (\rm{He\,{\small I}})/\mbox{$${\rm cm^{-2}}$$}\lesssim 13.5$$ and $$\log N (\rm{O\,{\small V}})/\mbox{$${\rm cm^{-2}}$$}\lesssim 13.3$$. Environmental properties of the galaxies, including galaxy overdensities, the total stellar mass and gravitational potential summed over all neighbours, and the presence of local ionizing sources, are found to have a significant impact on the observed CGM absorption properties. Specifically, massive galaxies and galaxies in overdense regions exhibit a higher rate of incidence of absorption. The CGM absorption properties in galaxy groups appear to be driven by the galaxy closest to the QSO sightline, rather than by the most massive galaxy or by mass-weighted properties. We introduce a total projected gravitational potential ψ, defined as −ψ/G = ∑Mhalo/dproj summed over all group members, to characterize the galaxy environment. This projected gravitational potential correlates linearly with the maximum density detected in each sightline (i.e. a power-law slope of $$0.95_{-0.14}^{+0.15}$$), consistent with higher pressure gas being confined in deeper gravitational potential wells. In addition, we find that the radial profile of cool gas density exhibits a decline from the inner regions to the outskirts, and the amplitude is consistent with the cool gas being in pressure balance with the hot halo. Finally, we note that the ionizing flux from nearby galaxies can elevate the N(H i)/N(He i) ratio, which provides a unique diagnostic of possible local sources contributing to the ionizing radiation field.
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This content will become publicly available on December 1, 2025
Gravitational lensing reveals cool gas within 10-20 kpc around a quiescent galaxy
While quiescent galaxies have comparable amounts of cool gas in their outer circumgalactic medium (CGM) compared to star-forming galaxies, they have significantly less interstellar gas. However, open questions remain on the processes causing galaxies to stop forming stars and stay quiescent. Theories suggest dynamical interactions with the hot corona prevent cool gas from reaching the galaxy, therefore predicting the inner regions of quiescent galaxy CGMs are devoid of cool gas. However, there is a lack of understanding of the inner regions of CGMs due to the lack of spatial information in quasar-sightline methods. We present integral-field spectroscopy probing 10–20 kpc (2.4–4.8 Re) around a massive quiescent galaxy using a gravitationally lensed star-forming galaxy. We detect absorption from Magnesium (MgII) implying large amounts of cool atomic gas (108.4–109.3 M⊙ with T~104 Kelvin), in comparable amounts to star-forming galaxies. Lens modeling of Hubble imaging also reveals a diffuse asymmetric component of significant mass consistent with the spatial extent of the MgII absorption, and offset from the galaxy light profile. This study demonstrates the power of galaxy-scale gravitational lenses to not only probe the gas around galaxies, but to also independently probe the mass of the CGM due to it's gravitational effect.
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- Award ID(s):
- 2108515
- PAR ID:
- 10644305
- Publisher / Repository:
- Communications Physics
- Date Published:
- Journal Name:
- Communications Physics
- Volume:
- 7
- Issue:
- 1
- ISSN:
- 2399-3650
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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