Narrow-band spectral imaging with sub-pixel resolution of the Chandra -ACIS archival observation of the ULIRG merger Arp 220 strongly suggests two Compton thick nuclei , spatially coincident with the infrared and radio emitting nuclear clusters , and separated by 1 ” ( \sim 365 pc at a distance of 76 Mpc ) .
These previously undetected highly obscured AGNs - West ( W ) and East ( E ) - are imaged , and separated from neighboring sources , in the 6-7 keV band , where the Fe-K lines dominate the emission .
The western nucleus is also detected at energies above 7 keV .
We estimate Fe-K equivalent width \sim 1 keV or possibly greater for both sources , and observed 2-10 keV luminosities L _ { X } < 3.2 \times { 10 } ^ { 40 } \mbox { erg } \mbox { s } ^ { -1 } ( W ) and < 1.3 \times { 10 } ^ { 40 } \mbox { erg } \mbox { s } ^ { -1 } ( E ) .
From the observed Fe-K lines luminosities , and assuming on the basis of the XMM-Newton spectrum that 40 % of this may be from the 6.4 keV component , we evaluate 2-10 keV intrinsic luminosities L _ { X } \sim 1 \times { 10 } ^ { 42 } \mbox { erg } \mbox { s } ^ { -1 } ( W ) and L _ { X } \sim 0.4 \times { 10 } ^ { 42 } \mbox { erg } \mbox { s } ^ { -1 } ( E ) .
The inferred X-ray luminosity is at least a factor of 3 higher than that expected from a pure starburst with the bolometric luminosity of Arp 220 .
For a typical AGN SED the bolometric luminosities are 5.2 \times { 10 } ^ { 43 } \mbox { erg } \mbox { s } ^ { -1 } ( W ) and 2 \times { 10 } ^ { 42 } \mbox { erg } \mbox { s } ^ { -1 } ( E ) .