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The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO excitation and atomic carbon in star-forming galaxies at z = 1-3

We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z = 0.46-3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations,...

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Main Authors: Boogaard, Leindert A. (Author) , Werf, Paul van der (Author) , Weiss, Axel (Author) , Popping, Gergö (Author) , Decarli, Roberto (Author) , Walter, Fabian (Author) , Aravena, Manuel (Author) , Bouwens, Rychard (Author) , Riechers, Dominik A. (Author) , González-López, Jorge (Author) , Smail, Ian (Author) , Carilli, Chris (Author) , Kaasinen, Melanie (Author) , Daddi, Emanuele (Author) , Cox, Pierre (Author) , Díaz-Santos, Tanio (Author) , Inami, Hanae (Author) , Cortes, Paulo C. (Author) , Wagg, Jeff (Author)
Format: Article (Journal)
Language:English
Published: 2020 October 19
In: The astrophysical journal
Year: 2020, Volume: 902, Issue: 2
ISSN:1538-4357
DOI:10.3847/1538-4357/abb82f
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.3847/1538-4357/abb82f
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Author Notes:Leindert A. Boogaard, Paul van der Werf, Axel Weiss, Gergö Popping, Roberto Decarli, Fabian Walter, Manuel Aravena, Rychard Bouwens, Dominik Riechers, Jorge González-López, Ian Smail, Chris Carilli, Melanie Kaasinen, Emanuele Daddi, Pierre Cox, Tanio Díaz-Santos, Hanae Inami, Paulo C. Cortes, and Jeff Wagg
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Summary:We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z = 0.46-3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations, we detect a total of 34 CO transitions with J = 1 up to 8 (and an additional 21 upper limits, up to J = 10) and 6 and transitions (and 12 upper limits). The CO(2-1) and CO(3-2)-selected galaxies, at and 2.5, respectively, exhibit a range in excitation in their mid-J = 4, 5 and high-J = 7, 8 lines, on average lower than (-brighter) BzK-color- and submillimeter-selected galaxies at similar redshifts. The former implies that a warm ISM component is not necessarily prevalent in gas mass-selected galaxies at . We use stacking and Large Velocity Gradient models to measure and predict the average CO ladders at z < 2 and z ≥ 2, finding and , respectively. From the models, we infer that the galaxies at z ≥ 2 have intrinsically higher excitation than those at z < 2. This fits a picture in which the global excitation is driven by an increase in the star formation rate surface density of galaxies with redshift. We derive a neutral atomic carbon abundance of , comparable to the Milky Way and main-sequence galaxies at similar redshifts, and fairly high densities (≥104 cm−3), consistent with the low-J CO excitation. Our results imply a decrease in the cosmic molecular gas mass density at z ≥ 2 compared to previous ASPECS measurements.
Item Description:Gesehen am 11.01.2021
Physical Description:Online Resource
ISSN:1538-4357
DOI:10.3847/1538-4357/abb82f

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