The Cosmic Ultraviolet Baryon Survey X: Density and Pressure Profiles of Clumpy Circumgalactic Gas at z=0.4−0.7
Abstract
The thermodynamic state and turbulent properties of the cool circumgalactic medium (CGM) are investigated for 23 galaxies and galaxy groups at intermediate redshift (z=0.4--0.7) in the Cosmic Ultraviolet Baryon Survey (CUBS) midz sample using background QSOs within the virial radius. Kinematically resolved absorption-line measurements from Hubble Space Telescope/COS and STIS spectra, combined with photoionization modeling, yield gas densities of nH≈10−4--10−2 cm−3, temperatures of T≈(1--5) × 104 K, and non-thermal line broadening of bNT≈2--30 km s−1 for individual cool clumps. Combined with published samples at similar redshifts, the results indicate that photoionization equilibrium accurately describes the cool CGM and that turbulent motions are predominantly subsonic. At fixed projected distance, cool-gas density decreases systematically with halo mass, while inferred cool-gas pressures in Mh≈1012--1013 M⊙ halos are consistent with hot-gas pressures inferred from stacked X-ray observations. The analysis uncovers a near constant total cool gas mass across a broad halo mass range, which directly translates to a declining baryon mass fraction in the cool phase from ≈ 6--19% in halos of Mh ≈ 1012 M⊙ to ≈ 0.6--1.5% in halos of Mh ≈ 1013 M⊙. Finally, several CUBS galaxies exhibit kinematically aligned low- and high-ionization species spanning up to two orders of magnitude in density, reflecting local fluctuations in the halo gas pressure.
Related
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BibTeX
@misc{kumar2026cosmic,
title = {{The Cosmic Ultraviolet Baryon Survey X: Density and Pressure Profiles of Clumpy Circumgalactic Gas at $z=0.4-0.7$}},
author = {Suyash Kumar and Hsiao-Wen Chen and Gwen C. Rudie and Zhijie Qu and Sean D. Johnson and Alexander Beckett and Sebastiano Cantalupo and Mandy C. Chen and David DePalma and Claude-André Faucher-Giguère and Sebastian Lopez and Nishant Mishra and Patrick Petitjean and Marc Rafelski and Michael Rauch and Joop Schaye and Fakhri S. Zahedy},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36088},
eprint = {2610.36088},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36088},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Cosmic Ultraviolet Baryon Survey X: Density and Pressure Profiles of Clumpy Circumgalactic Gas at z=0.4−0.7
AU - Suyash Kumar
AU - Hsiao-Wen Chen
AU - Gwen C. Rudie
AU - Zhijie Qu
AU - Sean D. Johnson
AU - Alexander Beckett
AU - Sebastiano Cantalupo
AU - Mandy C. Chen
AU - David DePalma
AU - Claude-André Faucher-Giguère
AU - Sebastian Lopez
AU - Nishant Mishra
AU - Patrick Petitjean
AU - Marc Rafelski
AU - Michael Rauch
AU - Joop Schaye
AU - Fakhri S. Zahedy
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.36088
UR - https://arxiv.org/abs/2610.36088
AB - The thermodynamic state and turbulent properties of the cool circumgalactic medium (CGM) are investigated for 23 galaxies and galaxy groups at intermediate redshift (z=0.4--0.7) in the Cosmic Ultraviolet Baryon Survey (CUBS) midz sample using background QSOs within the virial radius. Kinematically resolved absorption-line measurements from Hubble Space Telescope/COS and STIS spectra, combined with photoionization modeling, yield gas densities of n_H≈10^−4--10^−2 cm^−3, temperatures of T≈(1--5) × 10^4 K, and non-thermal line broadening of b_NT≈2--30 km s^−1 for individual cool clumps. Combined with published samples at similar redshifts, the results indicate that photoionization equilibrium accurately describes the cool CGM and that turbulent motions are predominantly subsonic. At fixed projected distance, cool-gas density decreases systematically with halo mass, while inferred cool-gas pressures in M_h≈10^12--10^13 M_⊙ halos are consistent with hot-gas pressures inferred from stacked X-ray observations. The analysis uncovers a near constant total cool gas mass across a broad halo mass range, which directly translates to a declining baryon mass fraction in the cool phase from ≈ 6--19% in halos of M_h ≈ 10^12 M_⊙ to ≈ 0.6--1.5% in halos of M_h ≈ 10^13 M_⊙. Finally, several CUBS galaxies exhibit kinematically aligned low- and high-ionization species spanning up to two orders of magnitude in density, reflecting local fluctuations in the halo gas pressure.
ER -