Kinematics of RR Lyraes in the Inner (Old?) Halo

Abstract

Zinn & Lee (1994, in prep.) have shown that the halo globular clusters with Rgc < 6 kpc are dominated by clusters with relatively blue horizontal branches for their metal abundance, which they interpret as a sign of their old relative ages. Of these “Old Halo” clusters having −1.7 < [Fe/H] < −0.8 dex, they find a net rotation about the galactic center of Vrot = 59 ± 22 km s−1, and a line-of-sight velocity dispersion of σlos = 62 ± 10 km s−1.