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Date and Time of the Query: 2019-04-21 T07:16:46 PDT
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For refcode 1998ApJ...496..133B:
Retrieve 20 NED objects in this reference.
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1998ApJ...496..133B A Search for Ultraviolet Emission from LINERs AARON J. BARTH Department of Astronomy, University of California, Berkeley, CA 94720- 3411 LUIS C. HO Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 ALEXEI V. FILIPPENKO Department of Astronomy, University of California, Berkeley, CA 94720- 3411 AND WALLACE L. W. SARGENT Palomar Observatory, 105-24 California Institute of Technology, Pasadena, CA 91125 Received 1997 August 28; accepted 1997 October 30 ABSTRACT We have obtained Hubble Space Telescope Wide Field and Planetary Camera 2 ultraviolet (UV) 2200 A and optical V-band images of 20 low- luminosity active galactic nuclei, most of which are spectroscopically classified as LINERs, in order to search for a possible photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two of the detected galaxies (NGC 3642 and NGC 4203) have compact, unresolved nuclear UV sources, while the remaining four UV sources (in NGC 4569, NGC 5005, NGC 6500, and NGC 7743) are spatially extended. Combining our data set with the earlier sample of Maoz et al., we find that the probability of detection of a nuclear UV source is greatest for galaxies having low internal reddening and low inclination, and we conclude that dust obscuration is the dominant factor determining whether or not a UV source is detected. Large emission-line equivalent widths and the presence of broad-line emission also increase the likelihood of detection of nuclear UV emission. Our results suggest that the majority of LINERs harbor obscured nuclear UV sources, which may be either accretion-powered active nuclei or young star clusters. Under the assumption that the compact UV sources in NGC 3642 and NGC 4203 have nonstellar spectra of slope f_{nu}_ is proportional to {nu}^-1^ extending into the extreme ultraviolet, the extrapolated ionizing fluxes are sufficiently strong to photoionize the narrow-line regions of these objects. The V-band images of many galaxies in our sample reveal remarkably strong dust lanes that may be responsible for obscuring some UV sources. Subject headings: galaxies: active-galaxies: nuclei-ultraviolet: galaxies
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