Francesco Haardt
University of Milan
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Publication
Featured researches published by Francesco Haardt.
The Astrophysical Journal | 1996
Francesco Haardt; Piero Madau
We present a detailed calculation of the propagation of AGN-like ionizing radiation through the intergalactic space. We model the ionization state of absorbing clouds, and show that the universe will be more opaque above
The Astrophysical Journal | 2003
Marta Volonteri; Francesco Haardt; Piero Madau
4\,
The Astrophysical Journal | 1999
Piero Madau; Francesco Haardt; Martin J. Rees
Ryd than previously estimated. Singly ionized helium in \Lya forest clouds and Lyman-limit systems is found to be very efficient in reprocessing soft X-ray, helium-ionizing photons into ultraviolet, hydrogen-ionizing ones. We demonstrate that a significant fraction of the absorbed primary photons (emitted, e.g., by quasar sources) will be reradiated by the photoionized gas through \Lya line emission, two-photon continuum, and recombination continuum radiation. In the light of new data and recent studies, we also reassess the contribution of the QSOs observed in optical surveys to the UV extragalactic background, and find that the stochastic reprocessing of quasar Lyman continuum radiation by hydrogen and helium along the line of sight will significantly affect the amplitude, spectral shape, and fluctuations properties of the metagalactic flux. In a scenario in which QSOs are the primary source of ionizing photons in the universe, the integrated \HI \Lya emission at
The Astrophysical Journal | 1993
Francesco Haardt; L. Maraschi
z=0
The Astrophysical Journal | 1994
Francesco Haardt; L. Maraschi; Gabriele Ghisellini
from photoionized \Lya clouds and Lyman-limit systems is found to be at a level of less than 5\% of current observational limits on the far-UV extragalactic radiation flux. We show that
Monthly Notices of the Royal Astronomical Society | 2007
Massimo Dotti; Monica Colpi; Francesco Haardt; Lucio Mayer
J_{912}
Monthly Notices of the Royal Astronomical Society | 2009
Rudy C. Gilmore; Piero Madau; Joel R. Primack; Rachel S. Somerville; Francesco Haardt
increases from
The Astrophysical Journal | 2015
Piero Madau; Francesco Haardt
\approx 10^{-23} \uvunits
The Astrophysical Journal | 2006
Alberto Sesana; Francesco Haardt; Piero Madau
at the present epoch to
Monthly Notices of the Royal Astronomical Society | 2007
Alberto Sesana; Marta Volonteri; Francesco Haardt
\approx 5\times 10^{-22}\uvunits