Fundamental plane distances to early-type field galaxies in the South Equatorial Strip - I. The spectroscopic data

Radial velocities and central velocity dispersions are derived for 238 E/S0 galaxies from medium-resolution spectroscopy. New spectroscopic data, have been obtained as part of a study of the Fundamental Plane distances and pe culiar motions of early-type galaxies in three selected directions of the S outh Equatorial Strip, undertaken in order to investigate the reality of la rge-scale streaming motion; results of this study have been reported in Mul ler et al. (1998). The new APM South Equatorial Strip Catalog (-17.degrees 5 < delta < +2.degrees 5) was used to select the sample of field galaxies i n three directions: (1) 15h10 - 16h10; (2) 20h30 - 21h501 (3) 00h10 - 01h30 . The spectra obtained have a median S/N per Angstrom of 23, an instrumenta l resolution (FWHM) of similar to 4 Angstrom, and the spectrograph resoluti on (dispersion) is similar to 100 km s(-1). The Fourier cross-correlation m ethod was used to derive the radial velocities and velocity dispersions. Th e velocity dispersions have been corrected for the size of the aperture and for the galaxy effective radius. Comparisons of the derived radial velocit ies with data from the literature show that our values are accurate to 40 k m s(-1). A comparison with results from Jorgensen et al. (1995) shows that the derived central velocity dispersion have an rms scatter of 0.036 in log sigma. There is no offset relative to the velocity dispersions of Das ies et al. (1987).