Astronomy and Astrophysics – Astrophysics
Scientific paper
2001-06-22
Astronomy and Astrophysics
Astrophysics
15 pages and 4 figures, submitted to ApJL
Scientific paper
We calculate the neutral hydrogen column density of self-absorption in QSOs predicted in a model where the QSOs are located in the same halos that contain the gas in damped Lya absorption systems. The model is parameterized by the probability P_0 that any halo has an active QSO. We assume that the QSOs ionize the gas, but do not expel or heat it. The derived HI column densities produce negligible Lyman limit absorption, even in the lowest luminosity QSOs, with an optical depth of only ~ 10% for luminosity L=0.01 L_*, when P_0=10^{-2}. We also compute the HeII Lyman limit self-absorption, which is slightly higher but still negligible. The self-absorption can be higher if the gas is highly clumped; only in this case the overall emissivity from QSOs could be significantly reduced due to absorption by the known damped Lya systems, to affect the predicted intensity of the ionizing background or the epoch of HeII reionization. The presence of the gas associated with damped absorption systems around QSOs could also be detected from the narrow Lya emission line, which should have and angular extent of 0.1 to 1'' in typical high-redshift QSOs.
Khairul Alam S. M.
Miralda-Escude' Jordi
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