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
Journal
Date Issued
2016
Author(s)
Aravena, M.
•
•
Walter, F.
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Da Cunha, E.
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Bauer, F. E.
•
Carilli, C. L.
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Daddi, E.
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Elbaz, D.
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Ivison, R. J.
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Riechers, D. A.
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Smail, I.
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Swinbank, A. M.
•
Weiss, A.
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Anguita, T.
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Assef, R. J.
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Bell, E.
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Bertoldi, F.
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Bacon, R.
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Bouwens, R.
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Cortes, P.
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Cox, P.
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Gónzalez-López, J.
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Hodge, J.
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Ibar, E.
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Inami, H.
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Infante, L.
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Karim, A.
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Le Le Fèvre, O.
•
Magnelli, B.
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Ota, K.
•
Popping, G.
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Sheth, K.
•
van der Werf, P.
•
Wagg, J.
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.
Volume
833
Issue
1
Start page
68
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...833...68A
Rights
open.access
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