NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T18:55:07 PDT
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For refcode 1988ApJ...330..751P:
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1988ApJ...330..751P CALCIUM INFRARED TRIPLET EMISSION IN ACTIVE GALACTIC NUCLEI S. E. PERSSON Mount Wilson and Las Campanas Observatories, Carnegie Institution of Washington Received 1987 November 19; accepted 1988 January 8 ABSTRACT Emission in the Ca II infrared triplet lines has been detected in at least nine, and probably 14, active galactic nuclei, out of a total of 40 surveyed. The Ca II line strengths are roughly correlated with the strength of optical Fe II emission and appear over a wide range of luminosity, BLR linewidth, and [O III]/H{beta} ratio. Calcium emission is thus a general property of AGN that have extremely dense and neutral gas near the active nucleus. The Ca II linewidth is correlated with that of the {lambda}8446 O I line, indicating that the Ca^+^ zone is intimately associated with the broad-line region. An exception is Mrk 231, in which the Ca II linewidths are significantly narrower than that of the O I line; a kinematically distinct region, perhaps in the form of a disk, is indicated. The level of ionization in the zone that gives rise to the optically thick calcium lines is very low, with neutral carbon providing the shielding for the Ca^+^ ions from the incident ultraviolet continuum. If these ultradense zones are heated by a nonradiative mechanism, as advocated by Collin-Souffrin, Joly, and others, and if such heating occurs in the accretion disk, then the kinematical information conveyed by the Ca II lines indicates that in general the BLR lies close to the disk plane. Subject headings: galaxies: nuclei - infrared: spectra
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