Milky Way rotation and the distance to the galactic center from Cepheid variables

The compiled photometry, reddenings, and radial velocities of Galactic Cepheids are fit with an axisymmetric Galactic rotation model. R(0) = 7.8 + or - 0.7 kpc and 2AR(0) = 228 + or - 19 km/s are derived. The LMC distance modulus is 18.45 on the same absolute calibration. Observed Cepheid gamma velocities appear on average to be 30 + or - 1 km/s more negative than the true corresponding center-of-mass velocities. The trend of increasing blueness toward larger Galactocentric radius confirms the radial metallicity gradient found spectroscopically. (Author)