Requirements for investigating the connection between Lyman-α absorption clouds and the large-scale distribution of galaxies

Vicki L. Sarajedini, Richard F. Green, Buell T. Jannuzi

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We model the requirements on observational data that would allow an accurate determination of the degree of association between Lyman-α absorbers and peaks in the redshift distribution of galaxies (large-scale structures like clusters of galaxies). We compare simulated distributions of low-redshift Lyman-α 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 catalogs of Lyman-α 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 Lyα 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-α absorbers are intrinsically uncorrelated with galaxies, we find that about eight 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-α absorbers are distributed with the peaks in the galaxy distribution, ∼38 lines of sight must be mapped for the distribution of both Lyman-α absorbers and galaxies in order to determine the fraction of absorbers distributed with the peaks of the galaxy distribution to an accuracy of 10%.

Original languageEnglish (US)
Pages (from-to)542-550
Number of pages9
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1996


  • Large-scale structure of universe
  • Methods: Statistical
  • Quasars: Absorption lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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