A deep search for a hot halo of NGC 5746: Constraining disk galaxy formation

Most galaxy formation models predict that massive lowredshift disk galaxies areembedded in extended hot halos of externally accreted gas. Yet observationalstudies have so far failed to detect soft Xray emission from such halos. Ourcosmological simulations, the first to produce fully realistic disk galaxies,suggest this is within reach but requires a factor of 10 increase in sensitivitycompared to existing Xray studies. We propose a deep observation of the massivespiral NGC5746, to decisively test for the presence of such a halo and constrainits properties. A detection will confirm a basic tenet of disk galaxy formationmodels, whereas a nondetection will seriously challenge these models and imposenew constraints on the growth mode and feedback history of disk galaxies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]