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2006MNRAS.371..356C - Mon. Not. R. Astron. Soc., 371, 356-362 (2006/September-1)
The detectability of HI 21-cm absorption in damped Lyman α systems.
CURRAN S.J. and WEBB J.K.
Abstract (from CDS):
We suggest that the lack of 21-cm absorption detections at high redshift arises from the fact that these DLAs are at similar angular diameter distances to the background quasars (i.e. the distance ratios are always close to unity). Above zabs∼ 1.6, the covering factor becomes largely independent of the DLA-QSO distance, making the high-redshift absorbers much less effective at covering the background continuum emission. At low redshift, small distance ratios are strongly favoured by the 21-cm detections, whereas large ratios are favoured by the non-detections. This mix of distance ratios gives the observed mix of detections and non-detections at zabs≲ 1.6. In addition to the predominance of large distance ratios and non-detections at high redshift, this strongly suggests that the observed distribution of 21-cm absorption in DLAs is dominated by geometric effects.
Abstract Copyright: 2006 The Authors. Journal compilation © 2006 RAS
Journal keyword(s): galaxies: ISM - quasars: absorption lines - cosmology: observations - early Universe
Simbad objects: 39
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