On the Exotic Hard X-ray Source Populations in the Hellas2XMM survey

Recent hard X-ray surveys have proven to be effective in discovering large numbers of X-ray sources that, despite the likely association with active nuclei, appear to be characterized by "peculiar" properties. Among these "exotic" source populations, we will focus on the nature of two classes of hard X-ray sources: those characterized by high X-ray-to-optical flux ratios -- a fraction of these are associated with the rather elusive Type 2 quasars -- and the X-ray bright optically normal galaxies, also known as XBONGs.Comment: On behalf of the HELLAS2XMM Collaboration, 6 pages, 4 figures, contribution to the Proceedings of the COSPAR Scientific Assembly, E1.3 "High-Energy Radiation from Black Holes: from Supermassive Black Holes to Galactic Solar Mass Black Holes", Paris (France), July 18-25, 2004, accepted for publication in Advances in Space Researc

Broad-band X-ray analysis of local mid-infrared selected Compton-thick AGN candidates

The estimate of the number and space density of obscured AGN over cosmic time still represents an open issue. While the obscured AGN population is a key ingredient of the X-ray background synthesis models and is needed to reproduce its shape, a complete census of obscured AGN is still missing. Here we test the selection of obscured sources among the local 12-micron sample of Seyfert galaxies. Our selection is based on a difference up to three orders of magnitude in the ratio between the AGN bolometric luminosity, derived from the spectral energy distribution (SED) decomposition, and the same quantity obtained by the published XMM-Newton 2-10 keV luminosity. The selected sources are UGC05101, NGC1194 and NGC3079 for which the available X-ray wide bandpass, from Chandra and XMM-Newton plus NuSTAR data, extending to energies up to ~30-45 keV, allows us an accurate determination of the column density, and hence of the true intrinsic power. The newly derived NH values clearly indicate heavy obscuration (about 1.2, 2.1 and 2.4 x10^{24} cm-2 for UGC05101, NGC1194 and NGC3079, respectively) and are consistent with the prominent silicate absorption feature observed in the Spitzer-IRS spectra of these sources (at 9.7 micron rest frame). We finally checked that the resulting X-ray luminosities in the 2-10 keV band are in good agreement with those derived from the mid-IR band through empirical L_MIR-L_X relations.Comment: 14 pages, 6 figures, accepted for publication in MNRA

ASCA view on High-Redshift Radio-Quiet Quasars

We briefly discuss the latest ASCA results on the X-ray spectral properties of high-redshift radio-quiet quasars.Comment: 4 pages, 1 figure, to appear in the Proceedings of the Conference "X-ray Astronomy '999: Stellar Endpoints, AGNs, and the Diffuse X-ray Background (September 6-10 - 1999

A deep look at the inner regions of the mini-BAL QSO PG 1126-041 with XMM-Newton

A long XMM-Newton observation of the mini-BAL QSO PG 1126-041 allowed us to detect a highly ionized phase of X-ray absorbing gas outflowing at v~15000 km/s. Physical implications are briefly discussed.Comment: 2 pages, 2 figures. Proceedings of "X.ray Astronomy 2009", Bologna 09/7-11/2009, AIP Conference Series, Eds. A. Comastri, M. Cappi, L. Angelin