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The contribution of Quasars to the Far Infrared Background
G. Risaliti, M. Elvis, R. Gilli
Recent observational results obtained with SCUBA, COBE and ISO have greatly improved our knowledge of the infrared and sub-mm background radiation. These limits become constraining…
Most Supermassive Black Holes must be Rapidly Rotating
M. Elvis, G. Risaliti, G. Zamorani
We use the integrated spectrum of the X-ray background and quasars Spectral Energy Distribution to derive the contribution of quasars to the energy output of the Universe. We find…
Ubiquitous variability of X-ray absorbing column densities in Seyfert 2 Galaxies
G. Risaliti, M. Elvis, F. Nicastro
We present a study of the variations in the absorbing column density of 25 X-ray defined Seyfert 2 galaxies, as inferred from hard X-ray observations, on timescales from months to…
A new population of soft X-ray weak quasars
G. Risaliti, A. Marconi, R. Maiolino +2
Quasars selected in optical surveys by means of their blue or UV excess are known to be strong emitters in the X-rays, except for Broad Absorption Line (BAL) objects. In this paper…