Evidence for a Population of High-Redshift Submillimeter Galaxies from Interferometric Imaging

Alison B. Peck, Atacama Large Millimeter-submillimeter Array
Joshua D. Younger, Harvard-Smithsonian Center for Astrophysics
Giovanni Fazio, Harvard-Smithsonian Center for Astrophysics
Jiasheng Huang, Harvard-Smithsonian Center for Astrophysics
Matthew Ashby, Harvard-Smithsonian Center for Astrophysics
Mark Gurwell, Harvard-Smithsonian Center for Astrophysics
Kamson Lai, Harvard-Smithsonian Center for Astrophysics
Glen Petitpas, Harvard-Smithsonian Center for Astrophysics
David Wilner, Harvard-Smithsonian Center for Astrophysics
Min Su Yun, University of Massachusetts Amherst
Grant Wilson, University of Massachusetts Amherst
Kimberly Scott, University of Massachusetts Amherst
Jason Austermann, University of Massachusetts Amherst
Thushara Perera, University of Massachusetts Amherst
Daisuke Iono, The University of Tokyo
Kotaro Kohno, The University of Tokyo
Ryohei Kawabe, NRO
David Hughes, Instituto Nacional de Astrofisica Optica y Electronica
Itziar Aretxaga, Instituto Nacional de Astrofisica Optica y Electronica
Tracy Webb, Université McGill
Alejo Martinez-Sansigre, Max Planck Institute for Astronomy
Eva Schinnerer, Max Planck Institute for Astronomy
Vernesa Smolcic, Max Planck Institute for Astronomy
Sungeun Kim, Sejong University
James Lowenthal, Smith College

This document has been relocated to https://scholarworks.smith.edu/ast_facpubs/39/

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We have used the Submillimeter Array (SMA) to image a flux limited sample of seven submillimeter galaxies at 345 GHz with 2" resolution. These galaxies were selected based on fluxes measured using the AzTEC camera on the JCMT at 1.1 mm. All of the sources (two radio-bright and five radio-dim) are unresolved, and we report positions accurate to ~0.2". All of these sources have multiple potential counterparts at other wavelengths within the original AzTEC beam. The astrometric accuracy offered by the SMA - which represents nearly an order of magnitude improvement over single dish imaging - enables us to unambiguously identify counterparts at other wavelengths observed with similarly high angular resolution. Compared to the two radio-bright sources in the sample, and those in previous studies, we find that the five radio-dim sources in the sample: 1) have systematically higher submm-to-radio flux ratios, 2) have lower IRAC 3.6-8.0 µm fluxes, and 3) are not detected at 24 µm. These properties, combined with size constraints at 345 GHz, suggest that the radio-dim submm galaxies in our sample are representative of a population of very dusty starbursts, with physical scales for submm continuum emission similar to local ultraluminous infrared galaxies and an average redshift higher than radio-bright sources. Without the benefit of this positional accuracy, an incorrect counterpart would have been identified for at least two of these sources, resulting in erroneous interpretations of their physical properties.