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The ALMA spectroscopic survey in the Hubble ultra deep field : evolution of the molecular gas in CO-selected galaxies.

Aravena, Manuel and Decarli, Roberto and Gónzalez-López, Jorge and Boogaard, Leindert and Walter, Fabian and Carilli, Chris and Popping, Gergö and Weiss, Axel and Assef, Roberto J. and Bacon, Roland and Bauer, Franz Erik and Bertoldi, Frank and Bouwens, Richard and Contini, Thierry and Cortes, Paulo C. and Cox, Pierre and da Cunha, Elisabete and Daddi, Emanuele and Díaz-Santos, Tanio and Elbaz, David and Hodge, Jacqueline and Inami, Hanae and Ivison, Rob and Fèvre, Olivier Le and Magnelli, Benjamin and Oesch, Pascal and Riechers, Dominik and Smail, Ian and Somerville, Rachel S. and Swinbank, A. M. and Uzgil, Bade and van der Werf, Paul and Wagg, Jeff and Wisotzki, Lutz (2019) 'The ALMA spectroscopic survey in the Hubble ultra deep field : evolution of the molecular gas in CO-selected galaxies.', The astrophysical journal., 882 (2). p. 136.


We analyze the interstellar medium properties of a sample of 16 bright CO line emitting galaxies identified in the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Large Program. This CO−selected galaxy sample is complemented by two additional CO line emitters in the UDF that are identified based on their MultiUnit Spectroscopic Explorer (MUSE) optical spectroscopic redshifts. The ASPECS CO−selected galaxies cover a larger range of star formation rates (SFRs) and stellar masses compared to literature CO emitting galaxies at z > 1 for which scaling relations have been established previously. Most of ASPECS CO-selected galaxies follow these established relations in terms of gas depletion timescales and gas fractions as a function of redshift, as well as the SFR–stellar mass relation (“galaxy main sequence”). However, we find that ∼30% of the galaxies (5 out of 16) are offset from the galaxy main sequence at their respective redshift, with ∼12% (2 out of 16) falling below this relationship. Some CO-rich galaxies exhibit low SFRs, and yet show substantial molecular gas reservoirs, yielding long gas depletion timescales. Capitalizing on the well-defined cosmic volume probed by our observations, we measure the contribution of galaxies above, below, and on the galaxy main sequence to the total cosmic molecular gas density at different lookback times. We conclude that main-sequence galaxies are the largest contributors to the molecular gas density at any redshift probed by our observations (z ∼ 1−3). The respective contribution by starburst galaxies above the main sequence decreases from z ∼ 2.5 to z ∼ 1, whereas we find tentative evidence for an increased contribution to the cosmic molecular gas density from the passive galaxies below the main sequence

Item Type:Article
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Publisher statement:© 2019. The American Astronomical Society. All rights reserved.
Date accepted:10 July 2019
Date deposited:08 October 2019
Date of first online publication:11 September 2019
Date first made open access:08 October 2019

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