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The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Multiband Constraints on Line-luminosity Functions and the Cosmic Density of Molecular Gas

Decarli, Roberto and Aravena, Manuel and Boogaard, Leindert and Carilli, Chris and González-López, Jorge and Walter, Fabian and Cortes, Paulo C. and Cox, Pierre and da Cunha, Elisabete and Daddi, Emanuele and Díaz-Santos, Tanio and Hodge, Jacqueline A. and Inami, Hanae and Neeleman, Marcel and Novak, Mladen and Oesch, Pascal and Popping, Gergö and Riechers, Dominik and Smail, Ian and Uzgil, Bade and van der Werf, Paul and Wagg, Jeff and Weiss, Axel (2020) The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Multiband Constraints on Line-luminosity Functions and the Cosmic Density of Molecular Gas. Astrophysical Journal, 902 (2). Art. No. 110. ISSN 1538-4357.

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We present a CO and atomic fine-structure line-luminosity function analysis using the ALMA Spectroscopic Survey (ASPECS) in the Hubble Ultra Deep Field. ASPECS consists of two spatially overlapping mosaics that cover the entire ALMA 3 mm and 1.2 mm bands. We combine the results of a line-candidate search of the 1.2 mm data cube with those previously obtained from the 3 mm cube. Our analysis shows that ~80% of the line flux observed at 3 mm arises from CO(2–1) or CO(3–2) emitters at z = 1–3 ("cosmic noon"). At 1.2 mm, more than half of the line flux arises from intermediate-J CO transitions (J_(up) = 3–6); ~12% from neutral carbon lines; and <1% from singly ionized carbon, [C ii]. This implies that future [C ii] intensity mapping surveys in the epoch of reionization will need to account for a highly significant CO foreground. The CO luminosity functions probed at 1.2 mm show a decrease in the number density at a given line luminosity (in units of L') at increasing J_(up) and redshift. Comparisons between the CO luminosity functions for different CO transitions at a fixed redshift reveal subthermal conditions on average in galaxies up to z ~ 4. In addition, the comparison of the CO luminosity functions for the same transition at different redshifts reveals that the evolution is not driven by excitation. The cosmic density of molecular gas in galaxies, ρ_(H₂), shows a redshift evolution with an increase from high redshift up to z ~ 1.5 followed by a factor ~6 drop down to the present day. This is in qualitative agreement with the evolution of the cosmic star formation rate density, suggesting that the molecular gas depletion time is approximately constant with redshift, after averaging over the star-forming galaxy population.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Decarli, Roberto0000-0002-2662-8803
Aravena, Manuel0000-0002-6290-3198
Boogaard, Leindert0000-0002-3952-8588
Carilli, Chris0000-0001-6647-3861
González-López, Jorge0000-0003-3926-1411
Walter, Fabian0000-0003-4793-7880
Cortes, Paulo C.0000-0002-3583-780X
Cox, Pierre0000-0003-2027-8221
da Cunha, Elisabete0000-0001-9759-4797
Daddi, Emanuele0000-0002-3331-9590
Díaz-Santos, Tanio0000-0003-0699-6083
Hodge, Jacqueline A.0000-0001-6586-8845
Inami, Hanae0000-0003-4268-0393
Neeleman, Marcel0000-0002-9838-8191
Novak, Mladen0000-0001-8695-825X
Oesch, Pascal0000-0001-5851-6649
Popping, Gergö0000-0003-1151-4659
Riechers, Dominik0000-0001-9585-1462
Smail, Ian0000-0003-3037-257X
Uzgil, Bade0000-0001-8526-3464
van der Werf, Paul0000-0001-5434-5942
Weiss, Axel0000-0003-4678-3939
Alternate Title:The ALMA Spectroscopic Survey in the HUDF: Multi-band constraints on line luminosity functions and the cosmic density of molecular gas
Additional Information:© 2020. The American Astronomical Society. Received 2020 June 23; accepted 2020 July 27; published 2020 October 19. F.W. and M.N. acknowledge support by the ERC Advanced Grant Cosmic-Gas (740246). Este trabajo cont ó con el apoyo de CONICYT + PCI + INSTITUTO MAX PLANCK DE ASTRONOMIA MPG190030. T.D.-S. acknowledges support from the CASSACA and CONICYT fund CAS-CONICYT Call 2018. J.H. acknowledges support of the VIDI research program with project number 639.042.611, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). D.R. acknowledges support from the National Science Foundation under grant numbers AST-1614213 and AST-1910107 and from the Alexander von Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers. H.I. acknowledges support from JSPS KAKENHI grant No. JP19K23462. I.R.S. acknowledges support from STFC (ST/T000244/1). Facilities: ALMA data: 2016.1.00324.L. 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 - .
Funding AgencyGrant Number
European Research Council (ERC)740246
Chinese Academy of Sciences South America Center for Astronomy (CASSACA)UNSPECIFIED
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)639.042.611
Alexander von Humboldt FoundationUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)JP19K23462
Science and Technology Facilities Council (STFC)ST/T000244/1
Subject Keywords:Molecular gas ; Galaxy evolution ; Luminosity function
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Molecular gas (1073); Galaxy evolution (594); Luminosity function (942)
Record Number:CaltechAUTHORS:20201021-160146710
Persistent URL:
Official Citation:Roberto Decarli et al 2020 ApJ 902 110
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106195
Deposited By: George Porter
Deposited On:22 Oct 2020 14:20
Last Modified:22 Oct 2020 14:20

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