The Lyman alpha forest towards B2 1225 + 317

Pushpa Khare, R. Srianand, D. G. York, R. Green, D. Welty, Ke Liang Huang, J. Bechtold

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We present observations of the Lyman alpha (Ly α) forest towards B2 1225 + 317 taken at a resolution of 18 km s-1. A clean sample of Ly α forest lines is extracted after a careful profile-fitting analysis and the removal of the absorption lines of heavy elements. The sample is analysed for statistical properties. Eighty per cent of the column densities are < 1014 cm-2. A single power law is inconsistent with the column density distribution and a steepening/break in the distribution is indicated. The average velocity dispersion parameter is 29.4 km s-1. We find 3σ evidence for a correlation between column density and the velocity dispersion parameter. The correlation, however, is mainly the result of narrow lines and weakens to 1.2σ if lines with a velocity dispersion parameter smaller than 20 km s-1 are excluded. An excess of line pairs with velocity separation ≤ 100 km s-1 over the expected number is found.

Original languageEnglish (US)
Pages (from-to)167-180
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1997
Externally publishedYes


  • Intergalactic medium
  • Quasars: absorption lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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