Detection of an ultrabright submillimetre galaxy in the Subaru/XMM–Newton Deep Field using AzTEC/ASTE

Creators: Ikarashi, S.; Bock, J. J.; Bradford, C. M.; Murphy, E. J.; Zmuidzinas, J.

Abstract

We report on the detection of an extremely bright (∼37 mJy at 1100 μm and ∼91 mJy at 880 μm) submillimetre galaxy (SMG), AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi), discovered in the 1100 μm observations of the Subaru/XMM–Newton Deep Field using AzTEC on ASTE. Subsequent CARMA 1300-μm and SMA 880-μm observations successfully pinpoint the location of Orochi and suggest that it has two components, one extended [full width at half-maximum (FWHM) of ∼4 arcsec] and one compact (unresolved). Z-Spec on CSO has also been used to obtain a wide-band spectrum from 190 to 308 GHz, although no significant emission/absorption lines were found. The derived upper limit to the line-to-continuum flux ratio is 0.1–0.3 (2σ) across the Z-Spec band. Based on the analysis of the derived spectral energy distribution from optical to radio wavelengths of possible counterparts near the SMA/CARMA peak position, we suggest that Orochi is a lensed, optically dark SMG lying at z ∼ 3.4 behind a foreground, optically visible (but red) galaxy at z ∼ 1.4. The deduced apparent (i.e., no correction for magnification) infrared luminosity (L_(IR)) and star formation rate (SFR) are 6 × 10^(13) L_⊙ and 11 000 M_⊙ yr^(−1), respectively, assuming that the L_(IR) is dominated by star formation. These values suggest that Orochi will consume its gas reservoir within a short time-scale (3 × 10^7 yr), which is indeed comparable to those in extreme starbursts like the centres of local ultraluminous infrared galaxies (ULIRGs).

Additional Information

© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Accepted 2011 April 14. Received 2011 April 12; in original form 2010 September 7. Article first published online: 22 Jul. 2011. We would like to thank everyone who helped staff and support the AzTEC/ASTE 2008 operations and data calibration, including N. Ukita, M. Tashiro, M. Uehara, S. Doyle, P. Horner, J. Cortes, J. Karakla, and G. Wallace. The ASTE project is driven by the Nobeyama Radio Observatory (NRO), a branch of the National Astronomical Observatory of Japan (NAOJ), in collaboration with the University of Chile and Japanese institutions including the University of Tokyo, Nagoya University, Osaka Prefecture University, Ibaraki University and Hokkaido University. Partial observations with ASTE were carried out remotely from Japan using NTT's GEMnet2 and its partner R&E networks, which are based on the AccessNova collaboration of the University of Chile, NTT Laboratories and the NAOJ. This study was supported in part by the MEXT Grant-in-Aid for Specially Promoted Research (No. 20001003). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Support for CARMA construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the James S. McDonnell Foundation, the Associates of the California Institute of Technology, the University of Chicago, the states of California, Illinois, and Maryland, and the National Science Foundation. The ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities.

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