2 Sample and observations

  The current sample has previously been selected for kinematical studies. It is composed of 87 early-type galaxies (S0s and ellipticals between E0 and E4). Kinematical parameters were published in a series of five papers (Prugniel & Simien 1994; Simien & Prugniel 1997a, 1997b, 1997c, 1998, hereafter collectively referred to as SP): the central velocity dispersion $\sigma_0$, the maximum rotational velocity $V_\mathrm{max}$ and, for some galaxies, the radial profile $\sigma(r)$ of the velocity dispersion, together with the rotation curve V(r) are given in these papers. Although the sample is not complete in terms of limiting apparent or absolute magnitude, the galaxies of the sample span a wide range of intrinsic luminosity (), of central velocity dispersion ( km s^-1), and, as a consequence, of metallicity. The observations were made at the 1.93 m telescope of the Observatoire de Haute-Provence equipped with the CARELEC long-slit spectrograph (Prugniel et al. 1992). The detector was a Tektronix CCD with $512\,\times\,512$ pixels of 27 $\mu$m each. The slit width projected on the sky was 2.2 arcsec. CARELEC transforms the focal ratio from f/15.5 at the Cassegrain focus to a value six times faster, providing a scale of 1.1 arcsec px^-1 in the spatial direction along the slit, and a FWHM spectoscopic resolution of 3.2 Å (or 1.8 px) corresponding to 1.8 Å px^-1. The selected setup with a reciprocal dispersion of 66 Å mm^-1 is always centered on the Mg$\,b\ \lambda5175$ Å triplet, and it provides nearly 900 Å of spectral coverage around it.

During seven observing runs in the period 1993 - 1995, a total of 210 spectra of early-type galaxies have been collected. Typically, two 45-min exposures were obtained for each galaxy. For comparison purposes, 17 galaxies of the sample were observed in more than one run. All details about the runs and the logs of observations can be found in SP. At least two template stars of spectral type in the range G8-III to K3-III were observed at the beginning of each night.