NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-18 T22:06:22 PDT
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For refcode 1999MNRAS.302...96I:
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NED Abstract

Copyright by Royal Astronomical Society. 1999MNRAS.302...96I An X-ray investigation of powerful far-infrared galaxies K. Iwasawa Institute of Astronomy, Madingley Road, Cambridge CB3 0HA Abstract We present ASCA results on four prototype powerful far-infrared galaxies, Mrk 231, Mrk 273, Arp 220 and NGC 6240. The soft X-ray spectra show signatures of thermal emission with temperatures of (0.5-1) x 10^7^ K, which is probably produced in starbursts. Their soft X-ray (0.5-2 keV) luminosities range from 4 x 10^40^ to 7 x 10^41^ erg s^-1^. The X-ray properties are examined in the context of a starburst. Evidence for a heavily obscured active nucleus is found in Mrk 273 and NGC 6240. The ASCA spectra of both galaxies show strong iron K emission-line features. The hard X-ray emission (> 3 keV) in NGC 6240 is most likely the reflected light of a hidden QSO, the intrinsic luminosity of which is suspected to be ~ 10^45^ erg s^-1^, comparable to the far-IR luminosity. The 2-10 keV emission, possibly related to an active galactic nucleus (AGN), is found in Mrk 231. The observed 2-10 keV luminosity is only ~ 2 x 10^42^ erg s^-1^, and the origin of the hard X-ray emission is uncertain because of the low quality of the present data. No evidence for an AGN is found in Arp 220 in the X-ray data. However, the soft X-ray emission originating in the starburst is also as weak as the H{alpha} nebula and near-IR continuum, despite the large far-IR excess. The possible existence of a powerful but heavily obscured (Compton-thick) AGN is discussed. Keywords : galaxies: active - galaxies: starburst - infrared: galaxies - X-rays: galaxies
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