(Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies. I. Multiwavelength identifications and redshift distribution

May 2015 • 2015A&A...577A..29M

Authors • Miettinen, O. • Smolčić, V. • Novak, M. • Aravena, M. • Karim, A. • Masters, D. • Riechers, D. A. • Bussmann, R. S. • McCracken, H. J. • Ilbert, O. • Bertoldi, F. • Capak, P. • Feruglio, C. • Halliday, C. • Kartaltepe, J. S. • Navarrete, F. • Salvato, M. • Sanders, D. • Schinnerer, E. • Sheth, K.

Abstract • We used the Plateau de Bure Interferometer (PdBI) to map a sample of 15 submillimetre galaxies (SMGs) in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey at S/N_{1.1 mm} = 4-4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. The angular resolution of our observations, 1''̣8, allowed us to accurately determine the positions of the target SMGs. Using a detection threshold of S/N_{1.3 mm}> 4.5 regardless of multiwavelength counterpart association, and 4 <S/N_{1.3 mm} ≤ 4.5 if a multiwavelength counterpart within 1''̣5 is also present, the total number of detections in our survey is 22. The most significant PdBI detection of S/N_{1.3 mm} = 10.3 is towards AzTEC19. Three of our detected SMGs (AzTEC21, 27, and 28; which corresponds to 20%) are marginally resolved at our angular resolution, and these sources are found to have elongated or clumpy morphologies and/or multiple components. Using optical to near-infrared photometric redshifts, available spectroscopic redshifts, and redshifts estimated from the radio-to-submm spectral index we infer a median redshift of tilde{z}= 3.20 ± 0.25 for our sample. To study the overall multiplicity and redshift distribution of flux-limited samples of SMGs we combined these sources with the 15 brightest JCMT/AzTEC SMGs detected at 1.1 mm, AzTEC1-15, and studied previously. This constitutes a complete, flux- and S/N-limited 1.1-mm selected sample. We find that the median redshift for the 15 brightest JCMT/AzTEC SMGs (tilde{z}= 3.05 ± 0.44) is consistent with that for AzTEC16-30. This conforms to recent observational findings that SMGs do not exhibit any significant trend between the redshift and (sub)mm flux density. For the combined AzTEC1-30 sample we derive a median redshift of tilde{z}= 3.17 ± 0.27, consistent with previous results based on mm-selected samples. We further infer that within the combined AzTEC1-30 sample 25 ± 9% of sources separate into multiple components.

Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Appendices are available in electronic form at http://www.aanda.org

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IPAC Authors
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Elise Furlan

Associate Scientist

Daniel Masters

Assistant Scientist