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A Probable BL Lac Object with Absorption Redshift 1.49

Published online by Cambridge University Press:  14 August 2015

R. W. Hunstead
Affiliation:
School of Physics, University of Sydney
J. C. Blades
Affiliation:
Anglo-Australian Observatory
H. S. Murdoch
Affiliation:
School of Physics, University of Sydney

Extract

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The radio source 1309–216 is identified with an 18m stellar object having a steep non-thermal continuum (α = 2.6, fν α ν−α) with no emission features. High resolution spectra obtained with the AAT reveal strong absorption due to the CIV doublet at redshifts 1.361, 1.489 and 1.491. In the strongest absorption system (za = 1.489) the SiIV doublet and possibly SiII are also detected. No information on the optical polarization is available but spectrophotometry at several epochs shows evidence for optical variability and the object is therefore classified tentatively as a BL Lac object.

The species found in absorption in 1309–216 are consistent either with ejection from a central source or absorption in the haloes of intervening galaxies. The velocity dispersions and column densities derived for the absorbing regions are comparable to those for gas in the LMC and in the halo of the galaxy.

Type
Research Article
Copyright
Copyright © Reidel 1980