THE ALMA SPECTROSCOPIC SURVEY in the HUBBLE ULTRA DEEP FIELD: MOLECULAR GAS RESERVOIRS in HIGH-REDSHIFT GALAXIES

Roberto Decarli, Fabian Walter, Manuel Aravena, Chris Carilli, Rychard Bouwens, Elisabete Da Cunha, Emanuele Daddi, David Elbaz, Dominik Riechers, Ian Smail, Mark Swinbank, Axel Weiss, Roland Bacon, Franz Bauer, Eric F. Bell, Frank Bertoldi, Scott Chapman, Luis Colina, Paulo C. Cortes, Pierre CoxJorge G�nzalez-L�pez, Hanae Inami, Rob Ivison, Jacqueline Hodge, Alex Karim, Benjamin Magnelli, Kazuaki Ota, Gerg� Popping, Hans Walter Rix, Mark Sargent, Arjen Van Der Wel, Paul Van Der Werf

Research output: Contribution to journalArticlepeer-review

Abstract

We study the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ∼1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities LIR > 1011L, i.e., a detection in CO emission was expected. Out of these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the CO-detected galaxies in the UDF tend to reside on the low- envelope of the scatter in the relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of ∼1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio (/M ) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor ∼2-5� smaller than those based on CO. When we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.

Original languageEnglish
Article number70
JournalAstrophysical Journal
Volume833
Issue number1
DOIs
Publication statusPublished - 8 Dec 2016

Keywords

  • galaxies: evolution
  • galaxies: ISM
  • galaxies: star formation
  • galaxies: statistics
  • instrumentation: interferometers
  • submillimeter: galaxies

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