期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 394, 期 1, 页码 L61-L65出版社
WILEY-BLACKWELL PUBLISHING, INC
DOI: 10.1111/j.1745-3933.2008.00610.x
关键词
galaxies: ISM; quasars: individual: images
资金
- National Science Foundation
- Max Planck Foundation
- NRAO
- Office of Naval Research
We have used the Very Long Baseline Array to image 18 quasars with foreground damped Lyman-alpha systems (DLAs) at 327, 610 or 1420 MHz, to measure the covering factor f of each DLA at or near its redshifted H I 21 cm line frequency. Including six systems from the literature, we find that none of 24 DLAs at 0.09 < z < 3.45 has an exceptionally low covering factor, with f similar to 0.45-1 for the 14 DLAs at z > 1.5 and f similar to 0.41-1 for the 10 systems at z < 1, and consistent covering factor distributions in the two subsamples. The observed paucity of detections of HI 21 cm absorption in high-z DLAs thus cannot be explained by low covering factors and is instead likely to arise due to a larger fraction of warm HI in these absorbers.
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