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Narrow-band spectral imaging with sub-pixel resolution of the Chandra-ACISarchival observation of the ULIRG merger Arp 220 strongly suggests two Comptonthick nuclei, spatially coincident with the infrared and radio emitting nuclearclusters, and separated by 1" (~ 365 pc at a distance of 76 Mpc). Thesepreviously undetected highly obscured AGNs - West (W) and East (E) - areimaged, and separated from neighboring sources, in the 6-7 keV band, where theFe-K lines dominate the emission. The western nucleus is also detected atenergies above 7 keV. We estimate Fe-K equivalent width ~ 1 keV or possiblygreater for both sources, and observed 2-10 keV luminosities L_X < 3.2 x 10^40erg/s (W) and <1.3 x 10^40 erg/s (E). From the observed Fe-K linesluminosities{, and assuming on the basis of the XMM-Newton spectrum that 40% ofthis may be from the 6.4 keV component, we evaluate 2-10 keV intrinsicluminosities L_X ~ 1 x 10^42 erg/s (W) and L_X ~ 0.4 x 10^42 erg/s (E). Theinferred X-ray luminosity is at least a factor of 3 higher than that expectedfrom a pure starburst with the bolometric luminosity of Arp 220. For a typicalAGN SED the bolometric luminosities are 5.2 x 10^43 erg/s (W) and 2 x 10^42erg/s (E).

Two Compton-Thick Active Nuclei in Arp 220?