Structure of the Galactic Halo Towards the North Galactic Pole
Abstract
We have used RR Lyrae and Blue HB stars as tracers of the old Galactic halo, in order to study the halo structure and the galactic rotation as a function of height above the plane. Our sample includes 40 RR Lyrae and 80 BHB stars that are about 2 to 15 kpc above the plane, in a roughly 250 deg2 area around the North Galactic Pole (NGP). We use proper motions (derived from the GSCII data base) and radial velocities to determine the rotation of the halo. From the whole sample the motion appears to be significantly more retrograde than the samples in the solar neighbourhood, confirming Majewski (1992) results and our own preliminary results based on 1/3 the present sample (Kinman et al. 2003; Spagna et al. 2003). However, the better statistics have now revealed the likely existence of two components, whose characteristics need an accurate analysis of systematic errors on the proper motions in order to be assessed in detail.
- Publication:
-
The Three-Dimensional Universe with Gaia
- Pub Date:
- January 2005
- DOI:
- 10.48550/arXiv.astro-ph/0410736
- arXiv:
- arXiv:astro-ph/0410736
- Bibcode:
- 2005ESASP.576..175K
- Keywords:
-
- Galaxy kinematics;
- Galaxy structure;
- Stars variables RR Lyr;
- Stars horizontal branch;
- Astrophysics
- E-Print:
- 4 pages, 4 figures, to appear in ``The Three Dimensional Universe with GAIA'', ESA SP-576, in press (needs aa.bst and Gaia2004.cls)