Galactic Fountains comma Galaxy Infall comma and the Dark Matter Content of NGC 891

We address two galaxy formation issues by studying the hot gas around theedgeon spiral NGC891. The primary issue is the origin of the hot halo, whichcan occur by infall onto the galaxy or from a galactic fountain generated bydisk SNe. We differentiate between models by measuring the gas metallicity,predicted to be low in one model and high in the other. Second, we will measurethe vertical component of the galaxy.s gravitational field, thereby lifting adegeneracy in mass models and permitting a unique determination of the darkmatter density in the baryondominated region. We accomplish this by measuringthe temperature and emission measure distribution perpendicular to the disk.Existing data prove feasibility but are not sufficiently deep. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]