Evidence for galaxy quenching in the green valley caused by a lack of a circumgalactic medium

Glenn G. Kacprzak, Nikole M. Nielsen, Hasti Nateghi, Christopher W. Churchill, Stephanie K. Pointon, Themiya Nanayakkara, Sowgat Muzahid, Jane C. Charlton

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7 Scopus citations


The relationship between a galaxy's properties and its circumgalactic medium (CGM) provides a unique view of how galaxies evolve. We present an interesting edge-on (i = 86°) disc galaxy (G1547) where the CGM is probed by a background quasar at a distance of 84 kpc and within 10° of the galaxy major axis. G1547 does not have any detectable CGM absorption down to stringent limits, covering H i (EWr <0.02 Å, log(N(H i)/cm-2) < 12.6) and a range of low and high ionization absorption lines (O i, C ii, N ii, Si ii, C iii, N iii, Si iii, C iv, Si iv, N v, and O vi). This system is rare, given the covering fraction of 1.00-0.04+0.00 for sub-L∗ galaxies within 50-100 kpc of quasar sightlines. G1547 has a low star formation rate (SFR, 1.1 M yr-1), specific SFR (sSFR, 1.5 × 10-10 yr-1), and ςSFR (0.06 M yr-1 kpc-2) and does not exhibit active galactic nucleus or star-formation-driven outflows. Compared to the general population of galaxies, G1547 is in the green valley and has an above average metallicity with a negative gradient. When compared to other H i absorption-selected galaxies, we find that quiescent galaxies with log(sSFR/yr-1) <-11 have a low probability (4/12) of possessing detectable H i in their CGM, while all galaxies (40/40) with log(sSFR/yr-1) >-11 have H i absorption. We conclude that sSFR is a good indicator of the presence of H i CGM. Interestingly however, G1547 is the only galaxy with log(sSFR/yr-1) >-11 that has no detectable CGM. Given the properties of G1547, and its absent CGM, it is plausible that G1547 is undergoing quenching due to a lack of accreting fuel for star formation, with an estimated quenching time-scale of 4 ± 1 Gyr. G1547 provides a unique perspective into the external mechanisms that could explain the migration of galaxies into the green valley.

Original languageEnglish (US)
Pages (from-to)2289-2301
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Jan 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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