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Date and Time of the Query: 2019-04-24 T23:06:50 PDT
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For refcode 1990ApJ...355...88G:
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1990ApJ...355...88G Pa{beta} MEASUREMENTS AND REDDENING IN SEYFERT 1.8 AND 1.9 GALAXIES ROBERT W. GOODRICH McDonald Observatory, University of Texas, Austin Received 1989 August 28; accepted 1989 November 28 ABSTRACT The class of active galactic nuclei known as Seyfert 1.8 and Seyfert 1.9 galaxies exhibit weak broad-Balmer emission lines and large Balmer decrements. One theory proposed to explain these characteristics is that the broad-line regions (BLRs) are reddened by dust along our line-of-sight. An alternative theory points out that BLR clouds with low-optical depths and low-ionization parameters can reproduce the observed line ratios. These two theories predict very different fluxes of the infrared hydrogen lines. In order to test the theories this paper presents measurements of the Pa{beta} emission lines of 10 intermediate Seyferts. Three objects known to have exhibited extreme spectral variability, NGC 2622, NGC 7603, and Mrk 1018, now all in Seyfert 1 states, are consistent with the reddening theory, as is IRAS 1958-183. Two other objects, Mrk 609 (a Seyfert 1.5) and UGC 7064, are more consistent with the optical depth/ionization parameter theory. Hence the Seyfert 1.8/1.9 class is evidently a heterogeneous one. Subject headings: galaxies: nuclei - galaxies: Seyfert - infrared: spectra
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