NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-03-26 T08:08:25 PDT
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For refcode 2001AJ....122..637H:
Retrieve 60 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2001AJ....122..637H THE SOFT X-RAY PROPERTIES OF NEARBY LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI AND THEIR CONTRIBUTION TO THE COSMIC X-RAY BACKGROUND EVE L. HALDERSON, EDWARD C. MORAN, AND ALEXEI V. FILIPPENKO Department of Astronomy, University of California, Berkeley, CA 94720-3411 AND LUIS C. HO Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 Received 2000 November 1; accepted 2001 March 2 ABSTRACT We have examined ROSAT soft X-ray observations of a complete, distance- limited sample of Seyfert and LINER galaxies. X-ray data are available for 46 out of 60 such objects which lie within a hemisphere of radius 18 Mpc. We have constructed radial profiles of the nuclear sources in order to characterize their spatial extent and, in some cases, to help constrain the amount of flux associated with a nuclear point source. PSPC data from ROSAT have been used to explore the spectral characteristics of the objects with sufficient numbers of detected counts. Based on the typical spectral parameters of these sources, we have estimated the luminosities of the weaker sources in the sample. We then explore the relationship between the soft X-ray and H{alpha} luminosities of the observed objects; these quantities are correlated for higher luminosity AGNs. We find a weak correlation at low luminosities as well, and we have used this relationship to predict L_X_ for the 14 objects in our sample that lack X-ray data. Using the results of the spatial and spectral analyses, we have compared the X-ray properties of Seyferts and LINERs, finding no striking differences between the two classes of objects. However, both types of objects often exhibit significant amounts of extended emission, which could minimize the appearance of differences in their nuclear properties. The soft X-ray characteristics of the type 1 and type 2 active galaxies in the sample are also discussed. We then compute the local X-ray volume emissivity of low-luminosity Seyferts and LINERs and investigate their contribution to the cosmic X-ray background. The 0.5-2.0 keV volume emissivity of 2.2 x 10^38^ ergs s^-1^ Mpc^-3^ we obtain for our sample suggests that low-luminosity AGNs produce at least 9% of the soft X-ray background. Key words: galaxies: active - galaxies: nuclei - galaxies: Seyfert - X-rays
Retrieve 60 NED objects in this reference.
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