People involved at OAB: Bragaglia, Buzzoni, Cacciari.
Field BHB stars and RR Lyrae variables are excellent tracers of the galactic halo stellar population. A detailed knowledge of their chemical and dynamical characteristics is therefore essential to understand how the Galaxy formed (e.g., hierarchical accretion/merging processes).
The questions of whether the high Galactic halo is in retrograde rotation and how the velocity dispersion and flattening of the halo vary with height above the Galactic plane are still controversial. They could be settled by studying halo stars nearer than about 10 kpc. In collaboration with Kinman (NOAO, USA) and Spagna (INAF-OATo) we are studying a sample of about 150 BHB and RR Lyrae stars near the North Galactic Pole by means of radial velocities and GSC-II proper motions for which we were granted a GSC-II pilot-program. Metallicities are estimated from various methods.
Photometric and spectroscopic data were collected during the last years; in particular spectra were collected in spring 2001, 2002 and 2003 (SARG@TNG, LRS@TNG). Results on the space motions based on about half of our data show that our sample is distinctly retrograde (Kinman et al. 2003, Cacciari et al. 2003).
A new field (towards the Anticenter) has been proposed in 2003, also with LRS@TNG, and observations of BHB stars have been obtained in January 2004.