X-Ray Emission from the Nuclear Region of Arp 220
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, 361005 (China)
- Department of Astronomy, University of Wisconsin, Madison, WI 53706-1582 (United States)
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{sup 40} erg s{sup −1} (western, W) and ∼3×10{sup 40} erg s{sup −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) (υ∼2000 km s{sup −1}) cannot be excluded. The 3σ upper limits on the neutral Fe–Kα flux of the nuclear regions correspond to the intrinsic AGN 2–10 keV luminosities of <1×10{sup 42} erg s{sup −1} (W) and <0.4×10{sup 42} erg s{sup −1} (E). For typical AGN spectral energy distributions the bolometric luminosities are <3×10{sup 43} erg s{sup −1} (W) and <8×10{sup 43} erg s{sup −1} (E), and black hole masses of <1×10{sup 5} M{sub ⊙} (W) and <5×10{sup 5} M{sub ⊙} (E) are evaluated for Eddington limited AGNs with a standard 10% efficiency.
- OSTI ID:
- 22872694
- Journal Information:
- Astrophysical Journal, Vol. 841, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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