Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-09-06
Astrophys.J. 643 (2006) 59-67
Astronomy and Astrophysics
Astrophysics
Accepted for publication in the Astrophysical Journal, 11 pages, 1 figure. Version 2: Added alternative method. Decreased fidu
Scientific paper
10.1086/502792
A generic assumption of ionization models of quasar absorption systems is that radiation from local sources is negligible compared with the cosmological background. We test this assumption and find that it is unlikely to hold for absorbers as rare as H I Lyman limit systems. Assuming that the absorption systems are gas clouds centered on sources of radiation, we derive analytic estimates for the cross-section weighted moments of the flux seen by the absorbers, of the impact parameter, and of the luminosity of the central source. In addition, we compute the corresponding medians numerically. For the one class of absorbers for which the flux has been measured: damped Ly-alpha systems at z~3, our prediction is in excellent agreement with the observations if we assume that the absorption arises in clouds centered on Lyman-break galaxies. Finally, we show that if Lyman-break galaxies dominate the UV background at redshift 3, then consistency between observations of the UV background, the UV luminosity density from galaxies, and the number density of Lyman limit systems requires escape fractions of order 10 percent.
No associations
LandOfFree
On the importance of local sources of radiation for quasar absorption line systems does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On the importance of local sources of radiation for quasar absorption line systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the importance of local sources of radiation for quasar absorption line systems will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-532322