Astronomy Reports

, Volume 62, Issue 12, pp 859–867 | Cite as

Observations of the Ly-α Forest

  • M. Demiański
  • A. DoroshkevichEmail author


We analyze four high resolution rich samples of Ly-α and metal lines (two at z ≥ 2 and two at z ≤ 0.2). We describe evolution of the observed Doppler parameters and absorbers separation and propose a model of the forest. We argue that all absorption lines are formed in gaseous caustics created in stable DM subclouds. The absorption lines are described by two local characteristics, the Doppler parameter and the column density of neutral hydrogen. We show that evolution of the Doppler parameter is very slow and its mean value increases by a factor ≤1.5 at redshifts 0 ≤ z ≤ 3. We show that absorbers separation increases as <dsep ∝ (1 + z)−2. We describe evolution of absorbers in the framework of a two component model: the first population represents absorbers with just one line created in compact stable DM clouds with random spatial distribution, and the second population includes absorbers with two, three and more absorption lines formed in more massive and extended random DM clouds. Slow evolution of the Doppler parameter indicates high stability of caustics and conditions within clouds. For absorbers of the second population relative velocity of lines slowly increases with time.


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Copyright information

© Pleiades Publishing, Ltd. 2018

Authors and Affiliations

  1. 1.Institute of Theoretical PhysicsUniversity of WarsawWarsawPoland
  2. 2.Department of AstronomyWilliams CollegeWilliamstownUSA
  3. 3.Astro Space CenterLebedev Physical Institute of the RASMoscowRussia
  4. 4.National Research Center “Kurchatov Institute,”MoscowRussia

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