Scintillation-induced Variability in Radio Absorption Spectra against Extragalactic Sources

Abstract

Spectral features absorbed against some radio quasars exhibit ~50mJy variations, with the lines varying both relative to the continuum and, when several lines are present, even relative to one another. We point out that such variability can be expected as a consequence of refractive scintillation caused by the interstellar medium of our Galaxy. Scintillation can cause independent variations between closely-spaced spectral lines, and can even alter the line profile. The background source need not be compact to exhibit spectral variability. The variability can be used to infer the parsec to sub-parsec scale structure of the intervening absorbing material. We discuss the importance of scintillation relative to other possible origins of spectral variability. The present theory is applied to account for the variations observed in the HI-absorbed quasar PKS 1127-145.

A&A in press, 17 pages, 3 figs

References in corpus (4)

• Rapid Variability and Annual Cycles in the Characteristic Time-scale of the Scintillating Source PKS 1257-326
• Annual modulation in the scattering of J1819+3845: peculiar plasma velocity and anisotropy
• Variable 21cm absorption at z=0.3127
• Small-Scale Variations of HI Spectra from Interstellar Scintillatio

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