1999AJ....118..895T

We present the results of a photometric and spectroscopic study of stars in four fields toward the inner disk and Galactic bulge. The fields are located symmetrically about the minor axis of the Milky Way at (l,b)=(-24°.8,-6°.0), (-8°.7,-6°.0), (+8°.4,-6°.0), and (+24°.4,-6°.1). We measured radial velocities and strengths of selected absorption-line indexes and derived the average reddening to each field, individual metallicities and photometric parallaxes for each star, and mean azimuthal rotation velocities and velocity dispersions for each field. We found that the stars are not strongly peaked in distribution at the tangent point or at bulgelike distances along any of the lines of sight. In each field, we find that velocity dispersion decreases as [Fe/H] increases, a correlation noted in many previous works. We also find that both velocity dispersion and [Fe/H] vary along each line of sight in a manner consistent with progressively sampling different populations (thin disk, bulge, thick disk, halo) at increasing distance; hence, the observed metallicity-velocity dispersion correlation is likely the result, at least in part, of the superposition of multiple populations viewed along the line of sight. We find that the disk stars in the (-24°.8,-6°.0) field are approaching the solar position at ∼50 km.s^–1 faster than the stars in the (+24°.4,-6°.1) field are moving away. Similarly, inner disk stars from the two inner fields have a velocity asymmetry of ∼35 km.s^–1. The velocity dispersions in these fields are also asymmetric; the -l fields have lower values than predicted for a circularly rotating exponential disk, while the +l fields have higher values. These kinematic asymmetries suggest that a barlike asymmetry exists in the inner disk of similar geometric positioning as the bar detected in the Galactic bulge. Comparison of the line-of-sight kinematics in our (+8°.4,-6°.0) field with the values of Minniti for a field at (+8°,+7°) indicates that the kinematics of the outer bulge is symmetric about the Galactic major axis. From the stars at bulgelike distances in our inner fields, we calculated a rotational velocity, and azimuthal velocity dispersion for the bulge. By linearly interpolating the values in the two fields, we found the projected mean rotation of the bulge to be 53.3±0.3 km.s^–1.kpc^–1, or 9.0±0.5 km.s^–1.deg^–1, in general agreement with other values from the literature.