285 research outputs found
Requirements for Investigating the Connection Between Lyman Alpha Absorption Clouds and the Large-Scale Distribution of Galaxies
We model the requirements on observational data that would allow an accurate
determination of the degree of association between Lyman alpha absorbers and
peaks in the redshift distribution of galaxies (large-scale structures like
clusters of galaxies). We compare simulated distributions of low-redshift Lyman
alpha absorption systems, constrained to be consistent with the distribution
observed with HST, with the large-scale distribution of galaxies determined
from pencil-beam redshift surveys. We estimate the amount of observational data
required from catalogues of Lyman alpha absorbers and galaxies to allow a
statistically significant test of the association of absorbers with large-scale
structures of galaxies.
We find that for each line-of-sight observed for Lyman alpha absorption lines
(assuming that the entire redshift range out to z=0.4 is observable), redshifts
must be obtained for at least 18 galaxies brighter than Mb=-18 and having
redshifts between 0.2 and 0.4. Based on the redshift surveys used in this
study, a search radius of 10' from the quasar line-of-sight is required. This
will ensure that all peaks in the galaxy redshift distribution are represented
by at least one galaxy in the observed sample. If Lyman alpha absorbers are
intrinsically uncorrelated with galaxies, we find that 8 lines-of-sight must be
observed to show that the distributions are different at the 95% confidence
level. However, if a fraction of the Lyman alpha absorbers are distributed with
the peaks in the galaxy distribution, 38 lines-of-sight must be mapped for the
distribution of both Lyman alpha absorbers and galaxies in order to determine
the fraction of absorbers distributed with the peaks of the galaxy distribution
to an accuracy of 10%.Comment: 17 pages LaTeX file, plus 6 uuencoded compressed .eps figures to be
printed seperately, to appear in Feb. 1, 1996 Ap
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