THE ALMA SPECTROSCOPIC SURVEY in the HUBBLE ULTRA DEEP FIELD: SEARCH for [CII] LINE and DUST EMISSION in 6 < z < 8 GALAXIES

M. Aravena, R. Decarli, F. Walter, R. Bouwens, P. A. Oesch, C. L. Carilli, F. E. Bauer, E. Da Cunha, E. Daddi, J. Gónzalez-López, R. J. Ivison, D. A. Riechers, I. Smail, A. M. Swinbank, A. Weiss, T. Anguita, R. Bacon, E. Bell, F. Bertoldi, P. CortesP. Cox, J. Hodge, E. Ibar, H. Inami, L. Infante, A. Karim, B. Magnelli, K. Ota, G. Popping, P. Van Der Werf, J. Wagg, Y. Fudamoto

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64 Citations (Scopus)

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 o. 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 o 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.

Original languageEnglish
Article number71
JournalAstrophysical Journal
Volume833
Issue number1
DOIs
Publication statusPublished - 2016 Dec 10
Externally publishedYes

Keywords

  • galaxies: ISM
  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: star formation
  • instrumentation: interferometers
  • submillimeter: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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