1 Introduction

The kinematics of the stars in the inner region of spiral galaxies can play a major role in the investigation of several key issues, a few of which are mentioned below.

To begin with, the observed motions within a bulge can be used to determine its mass and possibly its dynamical status, with the advantage (over ellipticals) that the inclination of the system is known. When the kinematics are available on a sample of bulges, they can be used to gauge, statistically, their degree of similarity with ellipticals. This can rely, for example, on the following points: a) the rotation/dispersion ($V/\sigma_0$) ratio (Kormendy 1993 and references therein); b) the $D_n - \sigma$ relation (Dressler 1987); and, c) the fundamental plane in its edge-on representation (e.g., Bender et al. 1992; Jablonka et al. 1996). Although large bulges are still thought to have been formed similarly to ellipticals, and before the disks, there is recent evidence that small bulges could have been formed later and differently (Franx 1993; Pfenniger 1993; Courteau et al. 1996); bulge kinematics provide an essential ingredient to the debate on their origin and evolution.

In a galaxy with a significant bulge, its mass is essential to the determination of the global mass distribution in the disk. Such applications often rely on a model fitted to the observed gas rotation curve (Broeils & Courteau 1997; Héraudeau & Simien 1997; Moriondo et al. 1998, to cite recent examples). But the motion of the gas in the innermost region is often an unreliable tracer of the circular rotation (Fillmore et al. 1986; Kent 1988; Bertola et al. 1995): this can strongly bias the bulge mass and, as a consequence, the disk mass as well; a way to bypass this problem is to adopt for the bulge the mass determined from the stellar kinematics.

In galaxies where the spectroscopic data extend well within the disk, one can address issues related to the old-disk dynamics (Bottema 1993). Finally, a better determination of the global stellar mass is likely to tighten the constraints on the distribution of dark matter (Bottema 1997; Courteau & Rix 1997; Persic & Salucci 1997 and references therein).

We note, however, that these applications can face several difficulties, arising from the contamination by the disk light and potential (Whitmore et al. 1984; Fillmore et al. 1986), the mixing of populations, and the effects of extinction by dust. Small bulges can be faint and difficult to resolve spectroscopically (and photometrically).

We have run a program of absorption spectroscopy with the purpose of determining the rotation curve and the velocity-dispersion profile in a sample of spiral galaxies; we present here a first set of results.