The mass of the Milky Way

We use the Jaffe model as a global mass distribution for the Galaxy and determine the circular velocity nu(c) and the Jaffe radius r(j) using the satellites of the Galaxy, estimates of the local escape velocity of stars, the constraints imposed by the known rotation curve of the disk, and the Local Group timing model. The models include the systematic uncertainties in the isotropy of the satellite orbits, the form of the stellar distribution function near the escape velocity, and the ellipticity of the M31/Galaxy orbit. If we include the Local Group timing constraint, then Leo I is bound, nu(c) = 220 +/- 30 km s(-1), and r(j) = 200 kpc (115 kpc less than or similar to r(j) less than or similar to 360 kpc) at 90% confidence. The satellite orbits are nearly isotropic with beta = 1 - sigma(theta)(2)/sigma(r)(2) = 0.2 (-0.5 less than or similar to beta less than or similar to 0.6), and the stellar distribution function near the escape velocity is f(epsilon) proportional to epsilon(k) with k(r) = 4.4 (1.6 less than or similar to K-r less than or similar to 8.5), where k(r) = k + 5/2. While not an accurate measurement of k, it is consistent with models of violent relaxation (k = 3/2). The mass inside 50 kpc is (4.9 +/- 1.1) x 10(11) M.. Higher mass models require that M31 is on its second orbit and that the halo is larger than the classical tidal limit of the Galaxy/M31 binary system. Such models must have a significant fraction of the Local Group mass in an extended Local Group halo. Lower mass models require that both M31 and Leo I are unbound, but there is no plausible mechanism to produce observed deviations of M31 and Leo I from their expected velocities in an unbound system. If we do not use the Local Group timing model, the median mass of the Galaxy increases significantly, and the error bars broaden. Using only the satellite, escape velocity, and disk rotation curve constraints, the median mass interior to 50 kpc is 3.9 (5.1), and the 90% confidence interval is 3.2-5.5 (4.0-6.4) without (with) Leo I in units of 10(11) M.. The lower bound without Leo I is 65% of the mass expected for a continuation of a flat rotation curve.