Buried Quasars in Ultra-luminous Infrared Galaxies

We were awarded l00kS of INTEGRAL spacecraft time (Priority A) to observe the ultraluminous infrared galaxy (ULIG) Mrk 2273 in order to measure the integrated flux of the 20-1003 KeV gamma-Ray emission, and to use this information to search for the presence of an highly obscured active galactic nucleus (AGN). With this observation we hope to be able to better assess the role of AGN in the complete class of ULIGs and therefore to better constrain their contribution to the hard X-ray and soft gamma-ray backgrounds. Our Priority A 100 kS observation of Mrk 273 was successfully carried out during revolution #73 using 4 separate exposures with the IBIS camera during May, 2003. Our IBIS observations of Mrk 273 were successfully executed, and the source was properly centered in the Field-of-view of the detectors. We are still in the process of interpreting the IBIS gamma-ray data.