Submillimeter Array identification of the millimeter-selected galaxy SSA22-AzTEC1: A protoquasar in a protocluster?

Y. Tamura, D. Iono, D. J. Wilner, M. Kajisawa, Y. K. Uchimoto, D. M. Alexander, A. Chung, H. Ezawa, B. Hatsukade, T. Hayashino, D. H. Hughes, T. Ichikawa, S. Ikarashi, R. Kawabe, K. Kohno, B. D. Lehmer, Y. Matsuda, K. Nakanishi, T. Takata, G. W. WilsonT. Yamada, M. S. Yun

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

We present results from Submillimeter Array (SMA) 860 μm subarcsecond astrometry and multiwavelength observations of the brightest millimeter (S 1.1mm = 8.4 mJy) source, SSA22-AzTEC1, found near the core of the SSA22 protocluster that is traced by Lyα-emitting galaxies at z = 3.09. We identify a 860 μm counterpart with a flux density of S860 μm = 12.2 ± 2.3 mJy and absolute positional accuracy that is better than 0′′.3. At the SMA position, we find radio-to-mid-infrared counterparts, whilst no object is found in Subaru optical and near-infrared deep images at wavelengths ≤1μm (J > 25.4 in AB, 2δ). The photometric redshift estimate, using flux densities at ≥24 μm, indicates z phot = 3.19+0.26-0.35, consistent with the protocluster redshift. We then model the near-to-mid-infrared spectral energy distribution (SED) of SSA22-AzTEC1, and find that the SED modeling requires a large extinction (AV ≈ 3.4 mag) of starlight from a stellar component with Mstar ∼ 1010.9M, assuming z = 3.1. Additionally, we find a significant X-ray counterpart with a very hard spectrum (Γeff =0.34+0.57 -0.61), strongly suggesting that SSA22-AzTEC1 harbors a luminous active galactic nuclei (AGNs; LX ≈ 3 × 1044 erg s-1) behind a large hydrogen column (NH ∼ 10 24 cm-2). The AGN, however, is responsible for only ∼10% of the bolometric luminosity of the host galaxy, and therefore the star formation activity likely dominates the submillimeter emission. It is possible that SSA22-AzTEC1 is the first example of a protoquasar growing at the bottom of the gravitational potential underlying the SSA22 protocluster.

Original languageEnglish
Pages (from-to)1270-1282
Number of pages13
JournalAstrophysical Journal
Volume724
Issue number2
DOIs
Publication statusPublished - 2010 Dec 1

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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