AB Aurigae is one of the brightest Herbig Ae stars (intermediate-mass pre-main-sequence stars) located 144 pc (~470 light years) away from the Sun, The near infrared image taken by the Subaru telescope shows a spiral pattern in the disk. We have observed the dust continuum emission and the CO(3-2) emission line with the SMA at an angular resolution of 1" (= 144 AU). The dust disk shown in the color of the left panel exhibits a central hole, which is possibly indicative of grain growth phenomenon due to planetesimal formation. The CO emission traces a gas disk in rotation, which departs noticeably from Keplerian; there is an outward radial motion along the spiral arm in the disk. The results suggest that there may be a giant (Jupiter-sized) planet forming inside the circumstellar disk of AB Aur responsible for the perturbation in morphology and kinematics. |