Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994mnras.271...94s&link_type=abstract
Monthly Notices of the Royal Astronomical Society, v.271, p.94.
Astronomy and Astrophysics
Astronomy
17
Scientific paper
We analyse the kinematics and dynamics of the system of blue horizontal branch field (BHBF) stars in the outer Galactic halo, fitting the kinematics with a simple model of the radial and tangential velocity dispersions in the halo as functions of Galactocentric radius r. The basic result is that the radial component Q of the halo's velocity ellipsoid decreases fairly rapidly beyond the solar circle. The decrease is from Q 140 km 1 at r = R0 to an asymptotic value of Q =80+ 16 km 5-1 at large r. The fairly rapid decrease in Ur is matched by an increase in the tangential velocity dispersion Q with increasing r. Hence the stellar halo velocity ellipsoid is shown to change markedly from radial anisotropy (fi 1.5) at the Sun to tangential anisotropy (p 0.6-0.8) in the outer halo (r> 20 kpc). These observations provide a very interesting new constraint on possible Galactic formation scenarios. Key words: stars: horizontal branch - stars: kinematics - Galaxy: halo - Galaxy: kinematics and dynamics.
Christensen Per Rex
Flynn Chris
Sommer-Larsen Jesper
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