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The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field : continuum number counts, resolved 1.2 mm extragalactic background, and properties of the faintest dusty star-forming galaxies.

Aravena, M. and Decarli, R. and Walter, F. and Da Cunha, E. and Bauer, F.E. and Carilli, C.L. and Daddi, E. and Elbaz, D. and Ivison, R.J. and Riechers, D.A. and Smail, I. and Swinbank, A.M. and Weiss, A. and Anguita, T. and Assef, R.J. and Bell, E. and Bertoldi, F. and Bacon, R. and Bouwens, R. and Cortes, P. and Cox, P. and Gónzalez-López, J. and Hodge, J. and Ibar, E. and Inami, H. and Infante, L. and Karim, A. and Le Le Fèvre, O. and Magnelli, B. and Ota, K. and Popping, G. and Sheth, K. and van der Werf, P. and Wagg, J. (2016) 'The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field : continuum number counts, resolved 1.2 mm extragalactic background, and properties of the faintest dusty star-forming galaxies.', Astrophysical journal., 833 (1). p. 68.

Abstract

We present an analysis of a deep (1σ = 13 μJy) cosmological 1.2 mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin2 covered by ASPECS we detect nine sources at \gt 3.5σ significance at 1.2 mm. Our ALMA-selected sample has a median redshift of z=1.6+/- 0.4, with only one galaxy detected at z > 2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cutoff and similar frequencies. Most galaxies have specific star formation rates (SFRs) similar to that of main-sequence galaxies at the same epoch, and we find median values of stellar mass and SFRs of 4.0× {10}10 {M}⊙ and ˜ 40 {M}⊙ yr-1, respectively. Using the dust emission as a tracer for the interstellar medium (ISM) mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from ˜0.1 to 1.0. As noted by previous studies, these values are lower than those using CO-based ISM estimates by a factor of ˜2. The 1 mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover 55% ± 4% of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover 80% ± 7% of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at z˜ 1{--}2, with stellar masses of (1-3) × 1010 M {}⊙ . For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3847/1538-4357/833/1/68
Publisher statement:© 2016. The American Astronomical Society. All rights reserved.
Date accepted:06 November 2016
Date deposited:09 March 2017
Date of first online publication:08 December 2016
Date first made open access:09 March 2017

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