We present results from Submillimeter Array ( SMA ) 860- \micron sub-arcsec astrometry and multiwavelength observations of the brightest millimeter ( S _ { \mathrm { 1.1 mm } } = 8.4 mJy ) source , SSA22-AzTEC1 , found near the core of the SSA22 protocluster that is traced by Ly \alpha emitting galaxies at z = 3.09 .
We identify a 860- \mu m counterpart with a flux density of S _ { \mathrm { 860 \mu m } } = 12.2 \pm 2.3 mJy and absolute positional accuracy that is better than 0 \farcs 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 \leq 1 ~ { } \micron ( J > 25.4 in AB , 2 \sigma ) .
The photometric redshift estimate , using flux densities at \geq 24 ~ { } \micron , indicates z _ { \mathrm { 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 ( A _ { V } \approx 3.4 mag ) of starlight from a stellar component with M _ { \mathrm { star } } \sim 10 ^ { 10.9 } M _ { \sun } , assuming z = 3.1 .
Additionally , we find a significant X-ray counterpart with a very hard spectrum ( \Gamma _ { \mathrm { eff } } = -0.34 ^ { +0.57 } _ { -0.61 } ) , strongly suggesting that SSA22-AzTEC1 harbors a luminous AGN ( L _ { \mathrm { X } } \approx 3 \times 10 ^ { 44 } ergs s ^ { -1 } ) behind a large hydrogen column ( N _ { \mathrm { H } } \sim 10 ^ { 24 } cm ^ { -2 } ) .
The AGN , however , is responsible for only \sim 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 .