  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.
