10 papers · 1 filter
Black Holes in Galactic Nuclei: the Promise and the Facts
Alessandro Marconi
It has long been suspected that Active Galactic Nuclei are powered by accretion of matter onto massive black holes and this belief implies their presence in the nuclei of most near…
Relic Black Holes and Type 2 Quasars
Alessandro Marconi, Marco Salvati
We follow the evolution of the Black Hole mass function in the assumption that mass accretion onto a massive BH is the powering mechanism of AGN activity. With reasonable assumptio…
HST Imaging in the Chandra Deep Field South: I. Multiple AGN Populations
E. J. Schreier, A. M. Koekemoer, N. A. Grogin +9
We present preliminary results from imaging three HST/WFPC2 fields in V and I within the Chandra Deep Field South (CDFS). HST's sensitivity and resolution are sufficient to reveal…
Sub-mm and X-ray background: two unrelated phenomena?
P. Severgnini, R. Maiolino, M. Salvati +9
Obscured AGNs are thought to contribute a large fraction of the hard X-ray background (2-10 keV), and have also been proposed as the powerhouse of a fraction of the SCUBA sources w…
The Elusive Active Nucleus of NGC 4945
A. Marconi, E. Oliva, P. P. van der Werf +4
We present new HST NICMOS observations of NGC 4945, a starburst galaxy hosting a highly obscured active nucleus that is one of the brightest extragalactic sources at 100 keV. The H…
The variability of the Seyfert galaxy NGC 2992: the case for a revived AGN
R. Gilli, R. Maiolino, A. Marconi +4
We report the transition to an active state of the nucleus in the Seyfert 1.9 galaxy NGC 2992, discovered by means of new hard X-ray data. While the 2-10 keV flux declined by a fac…