The CGM² Survey: Quenching and the Transformation of the Circumgalactic Medium

Abstract

This study addresses how the incidence rate of strong O vi absorbers in a galaxy’s circumgalactic medium (CGM) depends on galaxy mass and, independently, on the amount of star formation in the galaxy. We use Hubble Space Telescope/Cosmic Origins Spectrograph absorption spectroscopy of quasars to measure O vi absorption within 400 projected kpc and 300 km s−1 of 52 galaxies with M * ∼ 3 × 1010 M ⊙. The galaxies have redshifts 0.12 < z < 0.6, stellar masses 1010.1 M ⊙ < M * < 1010.9 M ⊙, and spectroscopic classifications as star-forming or passive. We compare the incidence rates of high column density O vi absorption (N O VI ≥ 1014.3 cm−2) near star-forming and passive galaxies in two narrow ranges of stellar mass and, separately, in a matched range of halo mass. In all three mass ranges, the O vi covering fraction within 150 kpc is higher around star-forming galaxies than around passive galaxies with greater than 3σ-equivalent statistical significance. On average, the CGM of star-forming galaxies with M * ∼ 3 × 1010 M ⊙ contains more O vi than the CGM of passive galaxies with the same mass. This difference is evidence for a CGM transformation that happens together with galaxy quenching and is not driven primarily by halo mass.

Circumgalactic Medium at High Halo Masses—Signatures of Cold Gas Depletion in Luminous Red Galaxies

“…Our results are also in agreement with a recent work of Tchernyshyov et al (2023), where the authors found that among galaxies with the same stellar or halo mass, O VI is more commonly detected in the CGM around star-forming galaxies than around passive galaxies. Tchernyshyov et al (2023) discussed two possible explanations for the detection of the O VI in the CGM around two passive galaxies from their sample, one was that the O VI is associated with another starforming interloping/neighboring galaxy, and the other was that galaxies that show O VI in their CGM were quenched more recently, and their CGM was still not transformed. Our results show that the former scenario might be more common.…”

The COS-Holes Survey: Connecting Galaxy Black Hole Mass with the State of the CGM

“…The final range of stellar and halo masses for the sample are log 10 M å /M e ∼ 10.2-10.9 and log 10 M halo /M e ∼ 11.45-12.51, respectively. We note that a stellar mass of ≈10 10.5 M e is representative of L å galaxies, but also can be a transitional stellar mass in terms of sSFR, which is known to correlate with CGM properties in intermediate ionization states (Tchernyshyov et al 2023). However, by keeping the range of stellar and halo masses relatively small, we minimize the scatter due to these properties and enable a controlled examination of the role SMBHs and SFR play in shaping the Terrazas et al 2017), while stellar masses are accurate to about ∼50%.…”

The Cool Circumgalactic Medium of Low-redshift Star-forming Galaxies. I. Empirical Model and Mean Properties

“…Other observational studies of cool gas around quiescent galaxies at z < 1 found similar results (Zahedy et al 2019;Chen et al 2020;Qu et al 2022). This work does not aim to answer the question of what causes galaxies to stop forming stars and what part the (cool) CGM plays in it (see Tchernyshyov et al 2023 for OVI-bearing gas). Our model can be applied to observations of quiescent galaxies in a future study.…”