HST/FOS Spectroscopy of Early--Type Radio Galaxies at z$\le$0.6

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Session 5 -- Cosmology and Gravitational Lenses
Display presentation, Monday, 9:20-6:30, Heller Lounge Room

[5.04] HST/FOS Spectroscopy of Early--Type Radio Galaxies at z$\le$0.6

S.M.Pascarelle, R.A.Windhorst (ASU), W.C.Keel (U of Al.), F.Bertola (Padova), P.J.McCarthy (OCIW), R.W.O'Connell (UVa), A.Renzini (Bologna), H.Spinrad (UCB)

We present the results of a Cycle 2 HST project to do systematic UV--spectroscopy of faint radio galaxies selected with 0.1$We will present the available FOS spectra (as of May 1993) and WFC images of four weak radio galaxy pairs with separations such that they can be observed as coordinated parallels to the primary FOS exposures. All spectra were processed with the best available darks, and reprocessed with the most recent FOS flats. The early--type galaxy 53W046 shows a moderately strong Ly--$\alpha$ emission line at z=0.530, possibly the first discovery of Ly--$\alpha$ in an early--type galaxy with z$\simeq$0.5, which cannot be done with IUE nor from the ground. The galaxy also has a faint UV--continuum which appears to turn up below 1500$\AA$ in the restframe. We subtracted the worst-- and best--case UV--sky values measured with UIT close to our NEP--field, and are currently assessing the possibility of a hot UV--upturn in the FOS spectra. We will use this data to set limits on the presence of any hot (old or young) stellar populations in early--type galaxies at z=0.1--0.6. This work is supported by NASA/STScI grant GO--3545--01--91A, and by the Alfred P. Sloan Foundation (to RAW).

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