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Submillimeter array identification of the millimeter-selected Galaxy SSA22-AzTEC1 : a protoquasar in a protocluster?

Tamura, Y. and Iono, D. and Wilner, D.J. and Kajisawa, M. and Uchimoto, Y.K. and Alexander, D.M. and Chung, A. and Ezawa, H. and Hatsukade, B. and Hayashino, T. and Hughes, D.H. and Ichikawa, T. and Ikarashi, S. and Kawabe, R. and Kohno, K. and Lehmer, B.D. and Matsuda, Y. and Nakanishi, K. and Takata, T. and Wilson, G.W. and Yamada, T. and Yun, M.S. (2010) 'Submillimeter array identification of the millimeter-selected Galaxy SSA22-AzTEC1 : a protoquasar in a protocluster?', Astrophysical journal., 724 (2). pp. 1270-1282.


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 S 860 μm = 12.2 ± 2.3 mJy and absolute positional accuracy that is better than 0farcs3. 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 <=1 μm (J > 25.4 in AB, 2σ). 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 M star ~ 1010.9 M sun, 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 (N H ~ 1024 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.

Item Type:Article
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Keywords:Galaxies, Formation, Starburst, Infrared, Quasars, Submillimeter, X-rays.
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Publisher statement:© 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
Date accepted:No date available
Date deposited:03 January 2014
Date of first online publication:December 2010
Date first made open access:No date available

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