Molecular line observations in two dusty star-forming galaxies at z = 6.9

Sreevani Jarugula, Joaquin D. Vieira, Axel Weiss, Justin S. Spilker, Manuel Aravena, Melanie Archipley, Matthieu Béthermin, Scott C. Chapman, Chenxing Dong, Thomas R. Greve, Kevin Harrington, Christopher C. Hayward, Yashar Hezaveh, Ryley Hill, Katrina C. Litke, Matthew A. Malkan, Daniel P. Marrone, Desika Narayanan, Kedar A. Phadke, Cassie ReuterKaja M. Rotermund

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20 Scopus citations


SPT0311-58 is the most massive infrared luminous system discovered so far during the Epoch of Reionization (EoR). In this paper, we present a detailed analysis of the molecular interstellar medium at z = 6.9, through high resolution observations of the CO(6-5), CO(7-6), CO(10-9), [C I](2-1), and p-H2O(21,1 -20,2) lines and dust continuum emissions with the Atacama Large Millimeter/submillimeter Array. The system consists of a pair of intensely star-forming, gravitationally lensed galaxies (labeled West and East). The intrinsic far-infrared luminosity is (16 ± 4) × 1012 Le in West and (27 ± 4) × 1011 Le in East. We model the dust, CO, and [C I] using non-local thermodynamic equilibrium radiative transfer models and estimate the intrinsic gas mass to be (5.4 ± 3.4) × 1011Me in West and (3.1 ± 2.7) × 1010Me in East. We find that the CO spectral line energy distribution in West and East are typical of high-redshift submillimeter galaxies (SMGs). The CO-to-H2 conversion factor (αCO) and the gas depletion timescales estimated from the model are consistent with the high-redshift SMGs in the literature within the uncertainties. We find no evidence of evolution of depletion time with redshift in SMGs at z > 3. This is the most detailed study of molecular gas content of a galaxy in the EoR to date, with the most distant detection of H2O in a galaxy without any evidence for active galactic nuclei in the literature.

Original languageEnglish (US)
Article number97
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 1 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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