A Far Ultraviolet Analysis of the Stellar Populations in Six Elliptical and S0 Galaxies

We have analyzed the far-ultraviolet (FUV) spectra of six elliptical and S0 galaxies in order to characterize the stellar population that produces the ultraviolet flux in these galaxies. The spectra were obtained using the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission aboard the Space Shuttle Endeavour in March 1995, and cover the spectral range from 820 to 1840 Å with a resolution of 3 Å. These data, together with the spectra of two galaxies observed with HUT on the Astro-1 mission, represent the only FUV spectra of early type galaxies that extend to the Lyman limit at 912 Å and therefore include the “turnover” in the spectral energy distribution below Lyman alpha. Using an extensive new grid of LTE and non-LTE synthetic spectra which match the HUT resolution and cover the relevant parameter space of temperature and gravity, we have constructed synthetic spectral energy distributions by integrating over various predicted stellar evolutionary tracks for horizontal