Velocities of Stars in Remote Galactic Satellites and the Mass of the Galaxy

We present observations of stars in four distant satellites of our Galaxy, Eridanus, Palomar 14, Leo 1, and Leo II. From these data we derive, using a technique of wavelength calibration which utilizes an etalon, the heliocentric systemic velocities of these systems, -21 +/- 4, 72 +/- 4, 285 +/- 3, and 70 +/- 4 km s^-1^, respectively. The value of the velocity for Leo I is in significant disagreement with previously published values. These systems are added to the remote satellite data base from which we estimate the mass of the Galaxy using a statistical method as well as timing arguments. The mass derived using the statistical techniques is 9.3^+4.1^_1.2_ x 10 M_sun_ assuming radial satellite orbits, and 12.5^+8.4^_3.2_ x 10^11^ M_sun_ assuming isotropic satellite orbits. A lower mass limit, 13 x 10^11^ M_sun_, was derived from timing arguments, for an age of the universe of 1.4 x 10^10^ yr and for the accepted Galactocentric distance of Leo I, and can change by at most 25% for reasonable changes to the input parameters. These values are valid only if Leo I is gravitationally bound to the Galaxy, and we present arguments which support this assumption. We also use the data to acquire preliminary values of the internal velocity dispersions and mass-to-light ratios in Leo I and II.