A Keplerian Disk around the Herbig Ae Star HD 169142

We present Submillimeter Array observations of the Herbig Ae star HD 169142 in 1.3 mm continuum emission and 12CO J = 2-1 line emission at ∼1.″5 resolution that reveal a circumstellar disk. The continuum emission is centered on the star position and resolved, and it provides a mass estimate of ∼0.02 M⊙ for the disk. The CO images show patterns in position and velocity that are well matched by a disk in Keplerian rotation with low inclination to the line of sight. We use radiative transfer calculations based on a flared, passive disk model to constrain the disk parameters by comparison to the spectral line emission. The derived disk radius is 235 AU, and the inclination is 13°. The model also necessitates modest depletion of the CO molecules, similar to that found in Keplerian disks around T Tauri stars.