Galaxy Photometry and X-Ray Astronomy

Data from Einstein Observatory X-ray observations of nearby normal galaxies are summarized and discussed. Consideration is given to the X-ray-binary-dominated emission of spiral and irregular galaxies and to the extended emission found in elliptical and S0 galaxies and attributed to gas at 10 to the 7th K. It is inferred that early-type galaxies have a significant interstellar medium in near hydrostatic equilibrium (i.e., with little or no galactic wind), that there is a cooling inflow of 0.1-1 solar mass/yr, and that star formation in elliptical galaxies (involving mainly low-mass stars contributing little optical light) proceeds at a rate only slightly lower than that for spiral galaxies.