2013/03/11 by A. Paggi, Paggi, Alessandro, G. Fabbiano +7 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.1303.2630
openalex publication_date 2013/03/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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" (~ 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 ~ 1 keV or possibly greater for both sources, and observed 2-10 keV luminosities LX < 3.2 x 1040 erg/s (W) and <1.3 x 1040 erg/s (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 LX ~ 1 x 1042 erg/s (W) and LX ~ 0.4 x 1042 erg/s (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 x 1043 erg/s (W) and 2 x 1042 erg/s (E).