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The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular Gas Reservoirs in High-redshift Galaxies

Decarli, Roberto and Walter, Fabian (2016) The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular Gas Reservoirs in High-redshift Galaxies. Astrophysical Journal, 833 (1). Art. No. 70. ISSN 0004-637X. doi:10.3847/1538-4357/833/1/70.

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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 L_(IR) > 10^(11) L_☉, 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- L_(IR) envelope of the scatter in the L_(IR)-L^'_(CO)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_(H2)/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.

Item Type:Article
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URLURL TypeDescription Paper
Decarli, Roberto0000-0002-2662-8803
Walter, Fabian0000-0003-4793-7880
Additional Information:© 2016 American Astronomical Society. Received 2016 May 3. Accepted 2016 September 6. Published 2016 December 8. We thank the anonymous referee for the positive feedback and useful comments. R.D. thanks Laura Zschaechner for insightful discussions. F.W., I.R.S., and R.J.I. acknowledge support through ERC grants COSMIC–DAWN, DUSTYGAL, and COSMICISM, respectively. M.A. acknowledges partial support from FONDECYT through grant 1140099. D.R. acknowledges support from the National Science Foundation under grant number AST-1614213 to Cornell University. F.E.B. and L.I. acknowledge Conicyt grants Basal-CATA PFB–06/2007 and Anilo ACT1417. F.E.B. also acknowledge support from FONDECYT Regular 1141218 (FEB), and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. I.R.S. also acknowledges support from STFC (ST/L00075X/1) and a Royal Society/Wolfson Merit award. Support for R.D. and B.M. was provided by the DFG priority program 1573 "The physics of the interstellar medium." A.K. and F.B. acknowledge support by the Collaborative Research Council 956, sub-project A1, funded by the Deutsche Forschungsgemeinschaft (DFG). PI acknowledges Conict grants Basal-CATA PFB–06/2007 and Anilo ACT1417. R.J.A. was supported by FONDECYT grant number 1151408. This paper makes use of the following ALMA data: [ADS/JAO.ALMA#2013.1.00146.S and 2013.1.00718.S.]. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The 3 mm part of ALMA project has been supported by the German ARC.
Funding AgencyGrant Number
European Research Council (ERC)COSMIC–DAWN
European Research Council (ERC)DUSTYGAL
European Research Council (ERC)COSMICISM
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1140099
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)Anilo ACT1417
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Science and Technology Facilities Council (STFC)ST/L00075X/1
Deutsche Forschungsgemeinschaft (DFG)1573
Deutsche Forschungsgemeinschaft (DFG)956
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1151408
Argelander-Institut für AstronomieUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: ISM; galaxies: star formation; galaxies: statistics; instrumentation: interferometers; submillimeter: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20161213-080831102
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Official Citation:Roberto Decarli et al 2016 ApJ 833 70
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72756
Deposited By: Ruth Sustaita
Deposited On:13 Dec 2016 17:18
Last Modified:11 Nov 2021 05:06

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