Theoretical Interpretation of the UV Obervations of Elliptical Galaxies from NASA Space Mission

During the past two decades, ultraviolet(UV) observations of elliptical galaxies and spiral bulges from the OAO-2 and HE satellites have established that the upturn in the specturm below 2000A is a common feature of these early-type system Because of its important implications for the formation of galaxies, astuonemical literature is replete with nurmerous discussions about the origin of the UV flux yet the situation remains controversal. New light on the problem is shed by the recent observations Some the Astro-1 space shuttle mission which suggest that the metal-poor horizontal-branch(HB) stars merit more detailed consideration for the origin of the UV flux It is shown here that such stars in these systems can indeedexplain the UV flux It is suggested that ttle obserred correlation between the UVupturn and total mass is due to the Possibility that the more massive galaxies tend to form earlier than the less massive galaxies as a result of mere efficient star formation in denser environments. It remains a task of mere detailed population synthesis nudels, now in progress, to put these results on a firmer quantitative basis.