34th Meeting of the AAS Division on Dynamical Astronomy, May 2003
3 Galactic Dynamics
Oral, Monday, May 5, 2003, 1:15-3:55pm,

[Previous] | [ 3] | [Next]

[3.06] Local Surface Density of the Galactic Disk

V.I. Korchagin, T.M. Girard (Yale U.), T.V. Borkova (Institute of Physics, Rostov University, Rostov-on-Don, Russia), D.I. Dinescu, W.F. van Altena (Yale U.)

Using parallaxes and proper motions of a kinematically and spatially unbiased sample of old bright red giant stars from the Hipparcos catalog with measured radial velocities from Barbier-Brossat & Figon (2000), we have re-estimated the surface density of the Galactic disk in the solar neighborhood within ± 0.4 kpc of the Sun. We determine the vertical distribution of the red giants as well as the vertical velocity dispersion of the sample, (14.4 ± 1.5 km/sec), and combine these to derive the surface density of gravitating matter in the Galactic disk, obtaining a value of 44 ± 9 Msun / pc2 within ± 400 pc. Furthermore, we find that this gravitating matter is concentrated within a layer of about ± 200 pc.

The derived values of surface density and concentration of gravitating matter indicate the presence of a thin, dark-matter component to the Galaxy. In the mid-plane of the disk, the volume density of this flattened component is a substantial fraction of the volume density of the observed matter.

This work was supported in part by grant No. AST 0098548 from the National Science Foundation.

[Previous] | [ 3] | [Next]

Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.