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Paper: Absorption toward Red BL Lac Objects
Volume: 156, Highly Redshifted Radio Lines
Page: 183
Authors: Stocke, J. T.; Rector, T. A.
Abstract: Based upon the prototypical high-z molecular absorber, PKS 1413+135, we present a summary of properties and search strategies for new high-z absorbers. It is suspicious that two of the four high-z molecular absorbers are BL Lac Objects (PKS 1413+135 & B2 0218+357), suggesting a link between the presence of the foreground absorber and the low equivalent width emission lines of BL Lacs. Also, based upon a new optical absorption line study of radio-selected BL Lac Objects (Stocke & Rector 1997), we find a large overabundance of intervening Mg II absorption line systems in these objects compared to quasars, which also seems to link low equivalent width emission lines to the presence of foreground absorption. Not only does this suggest that the optical characteristics of BL Lacs can be created by microlensing due to stars associated with foreground absorbing gas but also that red BL Lacs are a rich sample to search for new examples of foreground absorbers.
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