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X-Ray Emission from the Nuclear Region of Arp 220

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Abstract

  • We present an imaging and spectral analysis of the nuclear region of the ultraluminous infrared galaxy merger of Arp 220, using deep Chandra-ACIS observations summing up to ~ 300 {{ks}}. Narrowband imaging with subpixel resolution of the innermost nuclear region reveals two distinct Fe-K emitting sources, coincident with the infrared and radio nuclear clusters. These sources are separated by 1? (~380 pc). The X-ray emission is extended and elongated in the eastern (E) nucleus, like the disk emission observed in millimeter radio images, suggesting a starburst dominance in this region. We estimate an Fe-K equivalent width of ? 1 {keV} for both sources and observe 2-10 keV luminosities of ~ 2× {10}40 {{erg}} {{{s}}}-1 (western, W) and ~ 3× {10}40 {{erg}} {{{s}}}-1 (E). In the 6-7 keV band the emission from these regions is dominated by the 6.7 keV Fe xxv line, suggesting a contribution from collisionally ionized gas. The thermal energy content of this gas is consistent with the kinetic energy injection in the interstellar medium by SNe II. However, nuclear winds from a hidden active galactic nucleus (AGN) (\upsilon ~ 2000 {{km}} {{{s}}}-1) cannot be excluded. The 3? upper limits on the neutral Fe-K? flux of the nuclear regions correspond to the intrinsic AGN 2-10 keV luminosities of ) cannot be excluded. The 3? upper limits on the neutral Fe-K? flux of the nuclear regions correspond to the intrinsic AGN 2-10 keV luminosities of 42 {{erg}} {{{s}}}-1 (W) and (W) and 42 {{erg}} {{{s}}}-1 (E). For typical AGN spectral energy distributions the bolometric luminosities are (E). For typical AGN spectral energy distributions the bolometric luminosities are 43 {{erg}} {{{s}}}-1 (W) and (W) and 43 {{erg}} {{{s}}}-1 (E), and black hole masses of (E), and black hole masses of 5 {M}o (W) and (W) and 5 {M}o (E) are evaluated for Eddington limited AGNs with a standard 10% efficiency.

Publication Date

  • 2017

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