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Soft X-ray spectrum of BL Lacertae object AO 0235+164 as a tracer of elemental abundances at z approximately 0.5We report the soft X-ray spectrum of BL Lac object AO 0235+164, observed with the Einstein Observatory Imaging Proportional Counter (IPC). This object (z = 0.94) has an intervening galaxy (or a protogalactic disk) at z = 0.524 present in the line of sight, producing both radio and optical absorption lines in the background BL Lac continuum. The X-ray spectrum exhibits a substantial soft X-ray cutoff, corresponding to several times that expected from our own Galaxy; we interpret that excess cutoff as due to the intervening galaxy. The comparison of the hydrogen column density inferred from the 21 cm radio data and the X-ray absorption allows, in principle, the determination of the elemental abundances in the intervening galaxy. However, the uncertainties in both the H I spin temperature and X-ray spectral parameters only loosely restrict these abundances to be 2 +/- 1 solar, which even at the lower limit appears higher than that inferred from studies of samples of optical absoprtion-line systems.
Document ID
19950039610
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Madejski, Greg
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 16, 2013
Publication Date
September 10, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 432
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A71209
Funding Number(s)
CONTRACT_GRANT: NAG5-1813
Distribution Limits
Public
Copyright
Other

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