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., Wilson, G.W., Yamada, T. & Yun, M.S. (2010). Submillimeter Array Identification of the Millimeter-selected Galaxy SSA22-AzTEC1 A Protoquasar in a Protocluster? The astrophysical journal 724
Author(s) from Durham
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.