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The ALMA Spectroscopic Survey in the HUDF: CO Luminosity Functions and the Molecular Gas Content of Galaxies through Cosmic History

Decarli, Roberto; Walter, Fabian; Gónzalez-López, Jorge; Aravena, Manuel; Boogaard, Leindert; Carilli, Chris; Cox, Pierre; Daddi, Emanuele; Popping, Gergö; Riechers, Dominik; Uzgil, Bade; Weiss, Axel; Assef, Roberto J.; Bacon, Roland; Bauer, Franz Erik; Bertoldi, Frank; Bouwens, Rychard; Contini, Thierry; Cortes, Paulo C.; Cunha, Elisabete da; Díaz-Santos, Tanio; Elbaz, David; Inami, Hanae; Hodge, Jacqueline; Ivison, Rob; Fèvre, Olivier Le; Magnelli, Benjamin; Novak, Mladen; Oesch, Pascal; Rix, Hans-Walter; Sargent, Mark T.; Smail, Ian; Swinbank, A. Mark; Somerville, Rachel S.; Werf, Paul van der; Wagg, Jeff; Wisotzki, Lutz

The ALMA Spectroscopic Survey in the HUDF: CO Luminosity Functions and the Molecular Gas Content of Galaxies through Cosmic History Thumbnail


Authors

Roberto Decarli

Fabian Walter

Jorge Gónzalez-López

Manuel Aravena

Leindert Boogaard

Chris Carilli

Pierre Cox

Emanuele Daddi

Gergö Popping

Dominik Riechers

Bade Uzgil

Axel Weiss

Roberto J. Assef

Roland Bacon

Franz Erik Bauer

Frank Bertoldi

Rychard Bouwens

Thierry Contini

Paulo C. Cortes

Elisabete da Cunha

Tanio Díaz-Santos

David Elbaz

Hanae Inami

Jacqueline Hodge

Rob Ivison

Olivier Le Fèvre

Benjamin Magnelli

Mladen Novak

Pascal Oesch

Hans-Walter Rix

Mark T. Sargent

Rachel S. Somerville

Paul van der Werf

Jeff Wagg

Lutz Wisotzki



Abstract

We use the results from the ALMA large program ASPECS, the spectroscopic survey in the Hubble Ultra Deep Field (HUDF), to constrain CO luminosity functions of galaxies and the resulting redshift evolution of ρ(H2). The broad frequency range covered enables us to identify CO emission lines of different rotational transitions in the HUDF at z > 1. We find strong evidence that the CO luminosity function evolves with redshift, with the knee of the CO luminosity function decreasing in luminosity by an order of magnitude from ~2 to the local universe. Based on Schechter fits, we estimate that our observations recover the majority (up to ~90%, depending on the assumptions on the faint end) of the total cosmic CO luminosity at z = 1.0–3.1. After correcting for CO excitation, and adopting a Galactic CO-to-H2 conversion factor, we constrain the evolution of the cosmic molecular gas density ρ(H2): this cosmic gas density peaks at z ~ 1.5 and drops by a factor of ${6.5}_{-1.4}^{+1.8}$ to the value measured locally. The observed evolution in ρ(H2), therefore, closely matches the evolution of the cosmic star formation rate density ρ SFR. We verify the robustness of our result with respect to assumptions on source inclusion and/or CO excitation. As the cosmic star formation history can be expressed as the product of the star formation efficiency and the cosmic density of molecular gas, the similar evolution of ρ(H2) and ρ SFR leaves only little room for a significant evolution of the average star formation efficiency in galaxies since z ~ 3 (85% of cosmic history).

Citation

Decarli, R., Walter, F., Gónzalez-López, J., Aravena, M., Boogaard, L., Carilli, C., …Wisotzki, L. (2019). The ALMA Spectroscopic Survey in the HUDF: CO Luminosity Functions and the Molecular Gas Content of Galaxies through Cosmic History. Astrophysical Journal, 882(2), https://doi.org/10.3847/1538-4357/ab30fe

Journal Article Type Article
Acceptance Date Apr 3, 2019
Online Publication Date Sep 11, 2019
Publication Date Sep 10, 2019
Deposit Date Oct 8, 2019
Publicly Available Date Oct 8, 2019
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 882
Issue 2
DOI https://doi.org/10.3847/1538-4357/ab30fe

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Copyright Statement
© 2019. The American Astronomical Society. All rights reserved.






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