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

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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
Issue number2
Publication statusPublished - 2010 Dec 1


All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Tamura, Y., Iono, D., Wilner, D. J., Kajisawa, M., Uchimoto, Y. K., Alexander, D. M., Chung, A., Ezawa, H., Hatsukade, B., Hayashino, T., Hughes, D. H., Ichikawa, T., Ikarashi, S., Kawabe, R., Kohno, K., Lehmer, B. D., Matsuda, Y., Nakanishi, K., Takata, T., ... Yun, M. S. (2010). Submillimeter Array identification of the millimeter-selected galaxy SSA22-AzTEC1: A protoquasar in a protocluster? Astrophysical Journal, 724(2), 1270-1282.