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Date and Time of the Query: 2019-08-25 T00:30:35 PDT
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For refcode 1994ApJ...433L..65M:
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Copyright by American Astronomical Society. Reproduced by permission
1994ApJ...433L..65M THE TRUE NATURE OF IRAS-SELECTED, X-RAY-LUMINOUS "NORMAL" GALAXIES IN THE ROSAT ALL-SKY SURVEY EDWARD C. MORAN, JULES P. HALPERN, AND DAVID J. HELFAND Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027 E-mail: ed@falstaffphys.columbia.edu Received 1994 May 25; accepted 1994 July 12 ABSTRACT Luminous star-forming galaxies have often been suggested as potentially significant contributors to the cosmic X-ray background (XRB). Interest in this possibility has been rekindled by a recently published sample of 244 IRAS/ROSAT galaxies that includes 20 with extreme X-ray luminosities (L_x_ = 10^42-44^ ergs s^-1^) that are claimed to be "normal" spiral galaxies. To investigate whether or not these 20 X-ray- luminous spirals are truly normal star-forming galaxies, we have reexamined their classifications by obtaining new optical spectra of 13 of them, and by locating spectra in the literature for four. Our results indicate that 13 of the 17 objects are previously unrecognized Seyfert galaxies. Of the four star-forming non-Seyfert galaxies found in this sample, three are incorrectly identified as X-ray sources. Only one H II galaxy is a confirmed X-ray source, but it has L_x_ ~ 10^42^ ergs s^-1^ and is only about twice as luminous as the most luminous normal spirals detected previously at X-ray wavelengths. Thus, there are no H II galaxies with L_x_ substantially in excess of 10^42^ ergs s^-1^, and claims of a new class of X-ray-luminous spiral galaxies are not supported by this study. Subject headings: galaxies: Seyfert - galaxies: starburst - X-rays: galaxies
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