NASA/IPAC EXTRAGALACTIC DATABASE
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For refcode 1992MNRAS.256..149K:
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Copyright by Royal Astronomical Society. 1992MNRAS.256..149K Near-infrared imaging of hard X-ray selected active galaxies - II. The non-stellar continuum J. K. Kotilainen, M. J. Ward, C. Boisson, D. L. DePoy and M. G. Smith Institute of Astronomy Madingley Road, Cambridge CB3 0HA Department of Physics, Nuclear Physics laboratory Keble Road, Oxford OXl 3RH Observatoire de Paris, 92915 Meudon, France Department of Astronomy Ohio State University, Columbus, Ohio 43210, USA Joint Astronomy Centre, 665 Komohana St, Kilo, Hawaii 96720, USA Accepted 1991 November 26. Received 1991 November 20; in original form 1991 July 30 SUMMARY In this paper and in Paper I (this issue), we analyse and interpret the near-infrared observations of a complete hard X-ray selected sample of AGN, mainly optically classified as Seyfert 1s. The data are presented in Paper 1, in which we decompose the radial surface brightness profiles into a point source, bulge and disc components. In this paper we use the derived non-stellar/stellar fractions to subtract the stellar contribution present in small nuclear apertures. We examine the evidence for the presence of an underlying non-thermal power law, modified by dust reddening, as the origin of the non-stellar near-infrared component. We Find a correlation between the hard X-ray and near-infrared luminosities. This correlation does not, however, improve following the subtraction of the stellar component, as might be expected if there is an underlying power law connecting the two regions. Objects with steep near-infrared spectra are reddened and dominated by thermal emission from hot dust, whereas sources with flatter continua are mainly non-thermal. There is a weak or null correlation between the near-infrared spectral shape and reddening parameters. Some possible explanations for this are discussed. We conclude that the near-infrared continua of most Seyfert 1 galaxies are dominated by non-stellar components. Possible origins are hot dust emission, or a non-thermal component, which could be more important in the high-luminosity sources.
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