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Wiley, Monthly Notice- Royal Astronomical Society -Letters-, 1(529), p. L1-L6, 2023

DOI: 10.1093/mnrasl/slad189

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New constraints on the molecular gas content of a z ∼ 8 galaxy from JVLA CO(J = 2–1) observations

Journal article published in 2023 by Gareth C. Jones ORCID, Joris Witstok ORCID, Alice Concas ORCID, Nicolas Laporte ORCID
Distributing this paper is prohibited by the publisher
Distributing this paper is prohibited by the publisher

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Preprint: archiving forbidden
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Postprint: archiving restricted
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Published version: archiving forbidden
Data provided by SHERPA/RoMEO

Abstract

ABSTRACT As the primary fuel for star formation, molecular gas plays a key role in galaxy evolution. A number of techniques have been used for deriving the mass of molecular reservoirs in the early Universe (e.g. [C ii]158 µm, [C i], dust continuum), but the standard approach of CO-based estimates has been limited to a small number of galaxies due to the intrinsic faintness of the line. We present Jansky Very Large Array observations of the $z∼ \, 8.31$ galaxy MACS0416_Y1, targeting CO(2-1) and rest-frame radio continuum emission, which result in upper limits on both quantities. Adding our continuum limit to the published far-infrared (FIR) spectral energy distribution, we find a small non-thermal contribution to the FIR emission, a low-dust mass (${\rm {\log }}_{10}({\rm {\mathit{ M}}}_{\rm {D}}/{\rm M}_{⊙ })∼ 5$), and an abnormally high-dust temperature (${\rm \mathit{ T}}_{\rm D}\gtrsim \, 90\, \mathrm{ K}$) that may indicate a recent starburst. Assuming a low metallicity (Z/Z⊙ ∼ 0.25), we find evidence for $M_{{\rm {H}}_2}, \mathrm{ CO}\lesssim \, 10^{10}$ M⊙, in agreement with previous [C ii] investigations ($M_{{\rm {H}}_2},[\mathrm{ C}\,\small{\rm II}]\, ∼ \, 10^{9.6}$ M⊙). Upcoming JWST observations of this source will result in a precise determination of Z, enabling better constraints and an unprecedented view of the gaseous reservoir in this primordial starburst galaxy.