The Cosmic Ultraviolet Baryon Survey (CUBS). VII. On the Warm-hot Circumgalactic Medium Probed by O vi and Ne viii at 0.4 ≲ z ≲ 0.7

• Published in: The Astrophysical journal Vol. 968; no. 1; pp. 8 - 30
• Main Authors: Qu, Zhijie, Chen, Hsiao-Wen, Johnson, Sean D., Rudie, Gwen C., Zahedy, Fakhri S., DePalma, David, Schaye, Joop, Boettcher, Erin T., Cantalupo, Sebastiano, Chen, Mandy C., Faucher-Giguère, Claude-André, Li, Jennifer I-Hsiu, Mulchaey, John S., Petitjean, Patrick, Rafelski, Marc
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-06-2024; IOP Publishing
• Subjects: Absorption; Baryons; Circumgalactic medium; Fractions; Galactic halos; Galaxies; Galaxy evolution; Ionization; Kinematics; Metal concentrations; Quasar absorption line spectroscopy; Star & galaxy formation; Star formation; Stars & galaxies; Surveys; Ultraviolet astronomy; Velocity
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad410b

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲ z ≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O vi and Ne viii absorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs at zQSO ≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated O viλλ 1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s−1, while the rest show no trace of O vi to a detection limit of logNOVI/cm−2≈13.7. Meanwhile, only five galaxies or galaxy groups exhibit the Ne viiiλλ 770, 780 doublet absorption, down to a limiting column density of logNNeVIII/cm−2≈14.0. These O vi- and Ne viii-bearing halos reside in different galaxy environments with stellar masses ranging from logMstar/M⊙≈8 to ≈11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with logMstar/M⊙≈9–11 show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O vi absorption is broad with συ > 40 km s−1 for galaxies of logMstar/M⊙>9 within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O vi and Ne viii is suggested to be the dominant phase in sub-L* galaxies with logMstar/M⊙≈9–10 based on their high ionization fractions in the CGM.