Detection of a Substantial Molecular Gas Reservoir in a Brightest Cluster Galaxy at z = 1.7

Tracy M.A. Webb, James Lowenthal, Min Yun, Allison G. Noble, Adam Muzzin, Gillian Wilson, H. K.C. Yee, Ryan Cybulski, I. Aretxaga, D. H. Hughes

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


We report the detection of CO(2-1) emission coincident with the brightest cluster galaxy (BCG) of the high-redshift galaxy cluster SpARCS1049+56, with the Redshift Search Receiver (RSR) on the Large Millimeter Telescope (LMT). We confirm a spectroscopic redshift for the gas of z = 1.7091 ± 0.0004, which is consistent with the systemic redshift of the cluster galaxies of z = 1.709. The line is well fit by a single-component Gaussian with an RSR-resolution-corrected FWHM of 569 ± 63 km s-1. We see no evidence for multiple velocity components in the gas, as might be expected from the multiple image components seen in near-infrared imaging with the Hubble Space Telescope. We measure the integrated flux of the line to be 3.6 ± 0.3 Jy km s-1, and using = 0.8 Mo(K km s-1 pc2)-1, we estimate a total molecular gas mass of 1.1 ± 0.1 × 1011 M o and a M H2/M ∼ 0.4. This is the largest gas reservoir detected in a BCG above z > 1 to date. Given the infrared-estimated star formation rate of 860 ± 130 M o yr-1, this corresponds to a gas depletion timescale of ∼0.1 Gyr. We discuss several possible mechanisms for depositing such a large gas reservoir to the cluster center - e.g., a cooling flow, a major galaxy-galaxy merger, or the stripping of gas from several galaxies - but conclude that these LMT data are not sufficient to differentiate between them.

Original languageEnglish (US)
Article numberL17
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Aug 1 2017
Externally publishedYes


  • ISM: molecules
  • galaxies: clusters: individual (SpARCS1049+56)
  • galaxies: evolution
  • galaxies: starburst

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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