The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] Line and Dust Emission in 6

Journal
Date Issued
2016
Author(s)
Aravena, M.
•
•
Walter, F.
•
Bouwens, R.
•
Oesch, P. A.
•
Carilli, C. L.
•
Bauer, F. E.
•
Da Cunha, E.
•
Daddi, E.
•
Gónzalez-López, J.
•
Ivison, R. J.
•
Riechers, D. A.
•
Smail, I.
•
Swinbank, A. M.
•
Weiss, A.
•
Anguita, T.
•
Bacon, R.
•
Bell, E.
•
Bertoldi, F.
•
Cortes, P.
•
Cox, P.
•
Hodge, J.
•
Ibar, E.
•
Inami, H.
•
Infante, L.
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Karim, A.
•
Magnelli, B.
•
Ota, K.
•
Popping, G.
•
van der Werf, P.
•
Wagg, J.
•
Fudamoto, Y.
DOI
Abstract
We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for [C II] line emission and reach a limiting luminosity of L [C II] ∼ (1.6-2.5) × 108 L ☉. We identify 14 [C II] line emitting candidates in this redshift range with significances >4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S 1.2 mm = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M ☉ yr-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L [C II] versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.
Volume
833
Issue
1
Start page
71
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...833...71A
Rights
open.access
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