Shadowing of the Extragalactic Soft X-ray Background

We propose XMM EPIC observations of the nearby galaxies NGC 55 and NGC 3184.Our primary objective is to measure the depth of the shadows cast by the HIdisks of these galaxies against the soft extragalactic Xray background (XRB).The XMM measurements will define the intensity and spectrum of the extragalactic XRB in the softest accessible band (0.10.6 keV) and henceprovide important constraints on models of the XRB, the intergalactic ionizingflux at z0 and on any soft diffuse emission produced in a notsohot.. intergalactic medium. The Xray source populations and hot ISM of both galaxies will also be studied in unprecedented detail. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]