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Astron. Astrophys. 345, 691-711 (1999)

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The redshift evolution of Lyman-[FORMULA] absorbers

P. Valageas 1,2, R. Schaeffer 1 and J. Silk 2,3

1 Service de Physique Théorique, CEA Saclay, F-91191 Gif-sur-Yvette, France
2 Center for Particle Astrophysics, Department of Astronomy and Physics, University of California, Berkeley, CA 94720-7304, USA
3 Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, F-75014 Paris, France

Received 15 April 1998 / Accepted 16 February 1999


We present a model for the Lyman-[FORMULA] absorbers that treats all objects (from the low-density forest clouds to the dense damped systems) in a unified description. This approach is consistent with an earlier model of galaxies (luminosity function, metallicity) but also with the known description of the density field in the small-scale non-linear regime. We consider two cosmological models: a critical universe [FORMULA] with a CDM power-spectrum, and an open CDM universe with [FORMULA], [FORMULA]. We reproduce the available data on column density distribution as a function of redshift, the value of the main new parameter, the background ionizing UV flux, being consistent with the observed limits. This allows a quantitatively trustable analytical description of the opacity, mass, size, velocity dispersion and metallicity of these absorbers, over a range of column densities spanning 10 orders of magnitude. Moreover, together with an earlier model of galaxy formation this draws a unified picture of the redshift evolution of structures in the universe, from underdense clouds to massive high density galaxies, from weak to very deep potential wells.

Key words: cosmology: large-scale structure of Universe – galaxies: evolution – galaxies: intergalactic medium – galaxies: quasars: absorption lines

© European Southern Observatory (ESO) 1999

Online publication: April 28, 1999