NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
The HI Environment of Nearby Lyman-alpha AbsorbersWe present the results of a VLA and WSRT search for H I emission from the vicinity of seven nearby clouds, which were observed in Ly-alpha absorption with HST toward Mrk 335, Mrk 501, and PKS 2155-304. Around the absorbers, we searched a volume of 4O' x 40' x 1000 km/s; for one of the absorbers we probed a velocity range of only 600 km/s. The H I mass sensitivity (5 sigma) very close to the lines of sight varies from 5 x 10(exp 6) solar mass at best to 5 x 10(exp 8) solar mass at worst. We detected H I emission in the vicinity of four out of seven absorbers. The closest galaxy we find to the absorbers is a small dwarf galaxy at a projected distance of 68 h(exp -1) kpc from the sight line toward Mrk 335. This optically uncataloged galaxy has the same velocity (V = 1970 km/s) as one of the absorbers, is fainter than the SMC, and has an H I mass of only 4 x 10(exp 7) solar mass. We found a somewhat more luminous galaxy at exactly the velocity (V = 5100 km/s) of one of the absorbers toward PKS 2155-304 at a projected distance of 230 h(exp -1) kpc from the sight line. Two other, stronger absorbers toward PKS 2155-304 at V approx. 17,000 km/s appear to be associated with a loose group of three bright spiral galaxies, at projected distances of 300 to 600 h(exp -1) kpc. These results support the conclusions emerging from optical searches that most nearby Ly-alpha forest clouds trace the large-scale structures outlined by the optically luminous galaxies, although this is still based on small-number statistics. We do not find any evidence from the H I distribution or kinematics that there is a physical association between an absorber and its closest galaxy. While the absorbing clouds are at the systemic velocity of the galaxies, the H I extent of the galaxies is fairly typical, and at least an order of magnitude smaller than the projected distance to the sight line at which the absorbers are seen. On the other hand, we also do not find evidence against such a connection. In total, we detected H I emission from five galaxies, of which two were previously uncataloged and one did not have a known redshift. No H I emission was detected from the vicinity of the two absorbers, which are located in a void and a region of very low galaxy density; but the limits are somewhat less stringent than for the other sight lines. These results are similar to what has been found in optically unbiased H I surveys. Thus, presence of Ly-alpha absorbers does not significantly alter the H I detection rate in their environment.
Document ID
19970023675
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1086/118107
Authors
VanGorkom, J. H. (Columbia Univ. New York, NY United States)
Carilli, C. L. (National Radio Astronomy Observatory Socorro, NM United States)
Stocke, John T. (Colorado Univ. Boulder, CO United States)
Perlman, Eric S. (Colorado Univ. Boulder, CO United States)
Shull, J. Michael (Colorado Univ. Boulder, CO United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1996
Publication Information
Publication: The Astronomical Journal
Publisher: American Astronomical Society
Volume: 112
Issue: 4
ISSN: 0004-6256
Subject Category
Astronomy
Report/Patent Number
NASA-CR-204571
NAS 1.26:204571
Accession Number
97N23958
Funding Number(s)
CONTRACT_GRANT: NAGw-766
CONTRACT_GRANT: GO 3584.01-91A
CONTRACT_GRANT: NSF AST-90-23254
Distribution Limits
Public
Copyright
Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available