| Issue |
A&A
Volume 441, Number 1, October I 2005
|
|
|---|---|---|
| Page(s) | 9 - 21 | |
| Section | Cosmology (including clusters of galaxies) | |
| DOI | https://doi.org/10.1051/0004-6361:20052960 | |
| Published online | 13 September 2005 | |
Spectral energy distribution of the metagalactic ionizing radiation field from QSO absorption spectra
1
Department of Theoretical Astrophysics, Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia e-mail: lev@astro.ioffe.rssi.ru
2
Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
Received:
1
March
2005
Accepted:
30
May
2005
A computational procedure is presented to estimate the
spectral shape of the ionizing background
between 1 and 10 Ryd by analyzing optically thin absorption systems
in the spectra of high redshift quasars.
The procedure is based on the response surface
methodology from the theory of experimental design.
The shape of the recovered UV background at 
shows
a significant intensity decrease between 3 and 4 Ryd
compared to the metagalactic spectrum of Haardt & Madau (1996, ApJ, 461, 20).
This decrease is interpreted as produced
by 
Gunn-Peterson effect.
There are no features indicating a contribution from galaxies
to the UV background which is
therefore dominated by QSOs at .
Key words: cosmology: observations / line: formation / line: profiles / Galaxy: abundances / galaxies: quasars: absorption lines
© ESO, 2005
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