X-RAY-EMISSION AS A TOOL STUDY GALAXY FORMATION - THE CASE OF GREG (MS1111.9-3754)

An unusual optical red envelope has been observed for the first time a round the galaxy sitting at the center of the poor cluster MS1111.9-37 54, discovered in the EMSS x-ray survey. This optical envelope may be the product of accretion due to a massive cooling how, and this would be the first case in which the bulk of the cooling how material is see n. Otherwise, the evolution of the galaxy has allowed the formation of this cD type envelope with anomalous colors via a peculiar initial ma ss function. ROSAT PSPC and HRI data have been obtained for this objec t. The appearance of the X-ray emission is clearly structured at both small and large scales. A preliminary analysis of the ROSAT PSPC data shows a large X-ray emitting envelope of gas at a temperature of simil ar to 5 keV, while the ROSAT HRI image reveals an interesting bubble-l ike structure.