2 Sample and observations

Our initial aim was to obtain central kinematical data on bright, nearby spirals with available surface photometry. We selected galaxies with morphological type from Sa to Sc (both unbarred and barred), intermediate inclination, km s^-1, and absolute magnitude . This program has paralleled our collection of (mostly I-band) images of spiral galaxies (Héraudeau & Simien 1996: hereafter HS96); atmospheric conditions and telescope availability allowed us to get both photometric and spectroscopic data for about 50 galaxies only. Other objects were also added as targets for the spectroscopic observations because of their specific interest, regardless of the image availability. The final result is a sample which clearly lacks volume completeness and, therefore, statistical weight. It should nevertheless increase the available amount of such data significantly; in this paper, we present the first set of observations for which the reduction has been completed: 34 galaxies whose relevant catalog elements are presented in the first columns of Table 1.

Our kinematical observations were secured at the 1.93-m telescope of the Observatoire de Haute-Provence, equipped with the CARELEC long-slit spectrograph. The camera aperture ratio was f/2.6, and the receptor was a Tektronix with $512 \times 512$ pixels of 27 $\mu$m, corresponding to a projected size of 1.2''. The selected setup provided either: a) a wavelength range of $\approx$ 900 Å centered on Mg b, with a dispersion of 1.8 Å per pixel (corresponding to 104 km s^-1), or b) a range of $\approx$ 450 Å with a dispersion of 0.9 Å per pixel (52 km s^-1). The slit width, projected onto the plane of the sky, was 2.2''.

In May and November 1992, January and February 1993, a total of 14 nights of observation allowed us to collect data on the major axis of 34 galaxies. Table 2 (in electronic form only) presents the log of the observations. Typically, two 45- or 60-minutes exposures were obtained for each object; these exposure times were short enough to prevent the widening of the spectral lines due to flexures within the spectrograph, yet long enough to allow the measurement of kinematical parameters down to surface brightnesses of $\mu_V\simeq$ 21 mag arcsec^-2, with an accuracy for the velocity dispersion of less than 30 km s^-1 for most objects. For NGC 2903, NGC 3675, NGC 5055, and NGC 7331, spectra along the minor axis were also obtained. Each night, several template stars of types ranging between G8III and K2III were observed.

The atmospheric conditions were variable, with a seeing disk between 2'' and 3'' (FWHM) for most objects. Care has been taken to match the seeing conditions of the galaxy and star spectra, in order to ensure comparable spectroscopic resolutions.