Letter to the Editor
A high-resolution study of the evolution of the Lyman α forest in the redshift interval *
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: [ejanknecht,rbaade,dreimers]@hs.uni-hamburg.de
Corresponding author: E. Janknecht, firstname.lastname@example.org
Accepted: 6 July 2002
Spectroscopy with HST/STIS Echelle and VLT/UVES of the bright QSO HE 0515-4414 () offers for the first time the opportunity to study the Lyman α forest in the redshift range at a resolution ≤ 10 km s-1. The number density evolution of the Lyman α lines is well described by the power law approach d. We derive for the strong lines (), in agreement with the Lyman α forest evolution for . The expected slow-down in their evolution does not appear earlier than . For the weak lines () we find that the HE 0515-4414 data for follow the trend with known from observations, i.e. we confirm the difference in evolution between weak and strong lines. We use the two-point velocity correlation function (TPCF) to search for clustering of the Lyman α lines, yet we detect no excess in the TPCF on scales up to 10 000 km s-1.
Key words: cosmology: observations / intergalactic medium / quasars: Ly α forest / quasars: individual: HE 0515-4414
© ESO, 2002