منابع مشابه
Fluctuations in the Ionizing Background during and after Helium Reionization
The radiation background above the ionization edge of He II varies strongly during and after helium reionization, because the attenuation length of such photons is relatively short (. 40 Mpc) and because the ionizing sources (quasars) are rare. Here we construct analytic and Monte Carlo models to examine these fluctuations, including, for the first time, those during the reionization era itself...
متن کاملSpatial Correlations in the Helium-ionizing Background
After quasars ionize intergalactic He II at z ∼ 3, a large radiation field builds up above the He II ionization edge. Unlike the background responsible for H I ionizations, this field should be highly variable, thanks to the scarcity of bright quasars and the relatively short attenuation lengths (∼ 50 Mpc) of these high-energy photons. Recent observations of the He II and H I Lyα forests show t...
متن کاملThe Extragalactic Ionizing Background at Low Redshift
We present a measurement of the mean intensity of the hydrogen-ionizing background radiation field at low redshift using 906 Lyα absorption lines in 151 quasar spectra from the archives of the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST). Using a maximum likelihood technique and the best estimates possible for each QSO’s Lyman limit flux and systemic redshift, we find J(ν...
متن کاملEvolution of the Ionizing Background at High
The decrease in number density of Lyman{ clouds near the background quasar is an observational result which is often called thèproximity' orìnverse' eeect. It is thought that, for nearby clouds, the quasar's ux dominates the background radiation eld, increasing the ionization state of the clouds and reducing the (observed) H I column density. In this paper we analyse a sample of 11 quasars from...
متن کاملThe Inhomogeneous Ionizing Background Following Reionization
We study the spatial fluctuations in the hydrogen ionizing background in the epoch following reionization (z ∼ 5–6). The rapid decrease with redshift in the photon mean free path (m.f.p.), combined with the clustering of increasingly rare ionizing sources, can result in a very inhomogenous ionizing background during this epoch. We systematically investigate the probability density functions (PD...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 1992
ISSN: 0035-8711,1365-2966
DOI: 10.1093/mnras/258.1.36