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The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field : search for [CII] line and dust emission in 6 < z < 8 galaxies.

Aravena, M. and Decarli, R. and Walter, F. and Bouwens, R. and Oesch, P.A. and Carilli, C.L. and Bauer, F.E. and Da Cunha, E. and Daddi, E. and Gónzalez-López, J. and Ivison, R.J. and Riechers, D.A. and Smail, I. and Swinbank, A.M. and Weiss, A. and Anguita, T. and Bacon, R. and Bell, E. and Bertoldi, F. and Cortes, P. and Cox, P. and Hodge, J. and Ibar, E. and Inami, H. and Infante, L. and Karim, A. and Magnelli, B. and Ota, K. and Popping, G. and van der Werf, P. and Wagg, J. and Fudamoto, Y. (2016) 'The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field : search for [CII] line and dust emission in 6 < z < 8 galaxies.', Astrophysical journal., 833 (1). p. 71.

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.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3847/1538-4357/833/1/71
Publisher statement:© 2016. The American Astronomical Society. All rights reserved.
Date accepted:03 August 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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