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Dive into the research topics where Francesco Haardt is active.

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Featured researches published by Francesco Haardt.


The Astrophysical Journal | 1996

Radiative transfer in a clumpy Universe. 2. The Ultraviolet extragalactic background

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

The Assembly and Merging History of Supermassive Black Holes in Hierarchical Models of Galaxy Formation

Marta Volonteri; Francesco Haardt; Piero Madau

4\,


The Astrophysical Journal | 1999

Radiative Transfer in a Clumpy Universe. III. The Nature of Cosmological Ionizing Sources

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

X-ray spectra from two-phase accretion disks

Francesco Haardt; L. Maraschi

z=0


The Astrophysical Journal | 1994

A MODEL FOR THE X-RAY AND ULTRAVIOLET EMISSION FROM SEYFERT GALAXIES AND GALACTIC BLACK HOLES

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

Supermassive black hole binaries in gaseous and stellar circumnuclear discs: orbital dynamics and gas accretion

Massimo Dotti; Monica Colpi; Francesco Haardt; Lucio Mayer

J_{912}


Monthly Notices of the Royal Astronomical Society | 2009

GeV gamma-ray attenuation and the high-redshift UV background

Rudy C. Gilmore; Piero Madau; Joel R. Primack; Rachel S. Somerville; Francesco Haardt

increases from


The Astrophysical Journal | 2015

COSMIC REIONIZATION AFTER PLANCK: COULD QUASARS DO IT ALL?

Piero Madau; Francesco Haardt

\approx 10^{-23} \uvunits


The Astrophysical Journal | 2006

Interaction of massive black hole binaries with their stellar environment. I. Ejection of hypervelocity stars

Alberto Sesana; Francesco Haardt; Piero Madau

at the present epoch to


Monthly Notices of the Royal Astronomical Society | 2007

The imprint of massive black hole formation models on the LISA data stream

Alberto Sesana; Marta Volonteri; Francesco Haardt

\approx 5\times 10^{-22}\uvunits

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Piero Madau

University of California

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Giorgio Matt

University of Cambridge

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