1420003

We request a 2-year INTEGRAL program in AO-12 and AO-13 for 4 Ms observation in each year centred on 3C273 in order to obtain the deepest extragalactic wide field observation ever performed in the hard X-rays. The INTEGRAL mission provides us with the best wide angle imaging capabilities in the hard X-ray band above 20 keV available to date. In view of upcoming AOs and future missions we feel that it is time to think about legacy projects which will have a lasting impact on our knowledge of phenomena in the Universe far beyond the missions duration. Such a legacy can be the ultra-deep extragalactic field (UDF) which we propose to observe in the Virgo region centered on 3C273. Together with already exisiting data on this field INTEGRAL will thus achieve 21.5 Msec on this field and a detection sensitivity of 1.5e-12 erg/cm**2/sec for a 5-sigma point source significance in IBIS/ISGRI.This will derive around 100 source detections in total on this field out of which a significant fraction might be Compton thick and/or not previously known in the energy range below 10 keV. The scientific goals of this proposal are manifold: determining the luminosity function of AGN out to a redshift of about z=0.1 resolving 10% of the Cosmic X-ray Background (CXB) deriving an independent measurement of the CXB directly from the IBIS/ISGRI data performing a population study of AGN at hard X-rays in the low and high-luminosity domain and extending the spectral monitoring on 3C273 and of several Seyfert galaxies in the field. [truncated! Please see actual data for full text]