Scientific Seminars

AGNs in disguise

Alessandro Caccianiga
INAF-OA Brera

2007-11-28    14:00    Brera -

Active Galactic Nuclei (AGNs) usually distinguish themselves from other extragalactic sources by the presence, in their optical spectra, of strong emission lines and, in some cases, of a strong blue continuum. Nevertheless, these characteristic signatures are lacking in a number of sources whose AGN nature is inferred by other independent diagnostics (e.g. a high X-ray luminosity). Are these sources a new class of AGNs with unconventional properties or just "standard" AGN affected by an observational bias? In this talk I will present the results of a systematic investigation of the optically elusive AGNs found at relatively bright X-ray fluxes, selected in the XMM-Newton Bright Serendipitous (XBS) survey. The advantage of working at these bright fluxes is that complete spectroscopic information, both in the optical and in the X-ray band, can be obtained and sinergically used to unveil and characterize the properties of the hidden AGN.