NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-16 T00:24:02 PDT
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For refcode 1989PASP..101..949K:
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Copyright by Astronomical Society of the Pacific. Reproduced by permission
1989PASP..101..949K [S III] {lambda}{lambda}9069,9532 EMISSION IN ACTIVE GALACTIC NUCLEI SOFIA KIRHAKOS Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, Casilla 603, La Serena, Chile and Instituto de Pesquisas Espaciais, INPE, Caixa Postal 515, Sao Jose dos Campos, SP, Brazil AND M. M. PHILLIPS Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, Casilla 603, La Serena, Chile Received 1989 March 18, revised 1989 August 16 ABSTRACT Observations of the [S III] {lambda}{lambda}9069,9532 emission lines in the nuclear spectra of two Seyfert 2 galaxies, four LINERs, and two galaxies, with H II region nuclei are presented. These data are combined with published measurements to reexamine the suggestion by Diaz and collaborators that the relative strengths of the [S II] {lambda}{lambda}6716,6731 and [S III] {lambda} {lambda}9069,9532 lines in LINER nuclei provide a powerful method of distinguishing between photoionization and shock heating mechanisms. On the basis of this larger sample of objects, we find general support for the idea that many LINERs are photoionized and form a continuous sequence with Seyfert nuclei characterized by decreasing ionization parameter. Nevertheless, comparison with shock model calculations and published observations of the Kepler SNR shows that the [S II] and [S III] lines alone cannot be used to unambiguously rule out shock models as an alternate explanation for the emission-line spectra of typical LINERs. Indeed, in the case of the LINER nucleus of the luminous infrared galaxy NGC 6240, the observed strengths of these lines would appear to strongly favor shock heating as the dominant source of ionization. Thus, we conclude that both photoionization and shock heating are likely to play significant roles in any given LINER, with either process capable of dominating the observed emission-line spectrum. Key words: active galaxies-spectra
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