Affiliation:
1. Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
2. Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
3. Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching, Germany
4. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
Abstract
ABSTRACTThe molecular gas content of high-redshift galaxies is a highly sought-after property. However, H2 is not directly observable in most environments, so its mass is probed through other emission lines (e.g. CO, [C i], [C ii]), or through a gas-to-dust ratio. Each of these methods depends on several assumptions, and are best used in parallel. In this work, we extend an additional molecular gas tracer to high-redshift studies by observing hydrogen deuteride (HD) emission in the strongly lensed z = 5.656 galaxy SPT0346−52 with ALMA. While no HD(1–0) emission is detected, we are able to place an upper limit on the gas mass of $\rm M_{H_2}\lt 6.4\times 10^{11}\, M_{\odot }$. This is used to find a limit on the $L^{\prime }_{\mathrm{ CO}}$ conversion factor of $\rm \alpha _{CO}\lt 5.8\,M_{\odot}(K\,km\,s^{-1}\,pc^2)^{-1}$. In addition, we construct the most complete spectral energy distribution of this source to date, and fit it with a single-temperature modified blackbody using the nested sampling code multinest, yielding a best-fitting dust mass Mdust = 108.92 ± 0.02 M⊙, dust temperature 78.6 ± 0.5 K, dust emissivity spectral index β = 1.81 ± 0.03, and star formation rate SFR = 3800 ± 100 M⊙ yr−1. Using the continuum flux densities to estimate the total gas mass of the source, we find $\rm M_{H_2}\lt 2.4\times 10^{11}\, M_{\odot }$ , assuming subsolar metallicity. This implies a CO conversion factor of αCO < 2.2, which is between the standard values for MW-like galaxies and starbursts. These properties confirm that SPT0346−52 is a heavily starbursting, gas-rich galaxy.
Funder
H2020 European Research Council
Science and Technology Facilities Council
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
7 articles.
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