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Massive molecular gas reservoir in a luminous submillimeter galaxy during cosmic noon

Liu, Bin, Chartab, N., Nayyeri, H., Cooray, A., Yang, C., Riechers, D. A, Gurwell, M., Zhu, Zong-hong, Serjeant, S., Borsato, E., Negrello, M. ORCID:, Marchetti, L., Corsini, E. M. and van der Werf, P. 2022. Massive molecular gas reservoir in a luminous submillimeter galaxy during cosmic noon. Astrophysical Journal 929 (1) , 41. 10.3847/1538-4357/ac5745

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We present multiband observations of an extremely dusty star-forming lensed galaxy (HERS1) at z = 2.553. High-resolution maps of HST/WFC3, SMA, and ALMA show a partial Einstein ring with a radius of ∼3''. The deeper HST observations also show the presence of a lensing arc feature associated with a second lens source, identified to be at the same redshift as the bright arc based on a detection of the [N ii] 205 μm emission line with ALMA. A detailed model of the lensing system is constructed using the high-resolution HST/WFC3 image, which allows us to study the source-plane properties and connect rest-frame optical emission with properties of the galaxy as seen in submillimeter and millimeter wavelengths. Corrected for lensing magnification, the spectral energy distribution fitting results yield an intrinsic star formation rate of about 1000 ± 260 M⊙ yr−1, a stellar mass ${M}_{* }={4.3}_{-1.0}^{+2.2}\times {10}^{11}{M}_{\odot }$, and a dust temperature ${T}_{{\rm{d}}}={35}_{-1}^{+2}$ K. The intrinsic CO emission line (Jup = 3, 4, 5, 6, 7, 9) flux densities and CO spectral line energy distribution are derived based on the velocity-dependent magnification factors. We apply a radiative transfer model using the large velocity gradient method with two excitation components to study the gas properties. The low-excitation component has a gas density ${n}_{{{\rm{H}}}_{2}}={10}^{3.8\pm 0.6}$ cm−3 and kinetic temperature ${T}_{{\rm{k}}}={18}_{-5}^{+7}$ K, and the high-excitation component has ${n}_{{{\rm{H}}}_{2}}={10}^{3.1\pm 0.4}$ cm−3 and ${T}_{{\rm{k}}}={480}_{-220}^{+260}$ K. Additionally, HERS1 has a gas fraction of about 0.19 ± 0.14 and is expected to last 100 Myr. These properties offer a detailed view of a typical submillimeter galaxy during the peak epoch of star formation activity.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Additional Information: Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence
Publisher: American Astronomical Society
ISSN: 0004-637X
Date of First Compliant Deposit: 25 August 2022
Date of Acceptance: 13 February 2022
Last Modified: 06 May 2023 20:17

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