Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-07-26
Astrophys.J.629:L25-L28,2005
Astronomy and Astrophysics
Astrophysics
5 pages, including 2 figures; to appear in ApJ Letters, the 2005 August 10 issue
Scientific paper
10.1086/444377
We present a pilot study of the clustering properties of Lya absorbers with respect to known galaxies based on 112 Lya absorbers and 482 galaxies identified at z<0.5 along the sightline toward PKS0405-123. The principal goal is to determine the origin of Lya absorbers based on their cross-correlation amplitude with known galaxies and investigate a possible N(HI) dependence of the cross-correlation function. The main results of our study are as follows. (1) The cross-correlation function xi_{ga} measured using only emission-line dominated galaxies and Lya absorbers of log N(HI) >= 14 shows a comparable strength to the galaxy auto-correlation function xi_{gg} on co-moving, projection distance scales < 1 h^{-1} Mpc, while there remains a lack of cross-correlation signal when using only absorption-line dominated galaxies. This signifies a morphology-dependent xi_{ga} and indicates that strong absorbers of log N(HI) >= 14 and emission-line galaxies reside in the same halo population. (2) A maximum-likelihood analysis shows that Lya absorbers of log N(HI) < 13.6 are consistent with being more randomly distributed with respect to known galaxies. Finally, (3) we find based on this single sightline that the amplitude of xi_{ga} does not depend sensitively on N(HI) for strong absorbers of log N(HI) >= 13.6.
Chen Hsiao-Wen
Mulchaey John S.
Prochaska Jason Xavier
Weiner Benjamin J.
Williger Gerard. M.
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