2005ApJ...622L.133C

We have obtained high angular resolution (∼2") images of the ¹³CO (J=1⟶0) line and 2.7 mm continuum emission and slightly lower resolution images of ¹²CO (J=1⟶0) and C¹⁸O (J=1⟶0) line emission toward the Herbig Ae star AB Aurigae. We resolve a circumstellar disk of diameter 780 AU (FWHM) with a velocity pattern consistent with a purely rotational disk at inclination 21°.5 and position angle 58°.6. Using Keplerian disk models, we find a central-source dynamical mass of 2.8±0.1 M_☉ and a cutoff radius of 615 AU for the ¹³CO emission. The inclination, mass, and radius determined from ¹²CO and C¹⁸O observations agree with these values, given optical depth and abundance effects. As a result of the high angular resolution of our observations, we confirm the existence of spiral structure suggested by near-infrared scattered-light images and show that the spiral arms represent density contrasts in the disk.