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Published December 2010 | Published
Journal Article Open

Millimeter Imaging of MWC 758: Probing the Disk Structure and Kinematics


We investigate the structure and kinematics of the circumstellar disk around the Herbig Ae star MWC 758 using high-resolution observations of the ^(12)CO (3-2) and dust continuum emission at the wavelengths of 0.87 and 3.3 mm. We find that the dust emission peaks at an orbital radius of about 100 AU, while the CO intensity has a central peak coincident with the position of the star. The CO emission is in agreement with a disk in Keplerian rotation around a 2.0 M_⊙ star, confirming that MWC 758 is indeed an intermediate-mass star. By comparing the observation with theoretical disk models, we derive that the disk surface density Σ(r) steeply increases from 40 to 100 AU and decreases exponentially outward. Within 40 AU, the disk has to be optically thin in the continuum emission at millimeter wavelengths to explain the observed dust morphology, though our observations lack the angular resolution and sensitivity required to constrain the surface density on these spatial scales. The surface density distribution in MWC 758 disk is similar to that of "transition" disks, though no disk clearing has been previously inferred from the analysis of the spectral energy distribution (SED). Moreover, the asymmetries observed in the dust and CO emission suggest that the disk may be gravitationally perturbed by a low-mass companion orbiting within a radius of 30 AU. Our results emphasize that SEDs alone do not provide a complete picture of disk structure and that high-resolution millimeter-wave images are essential to reveal the structure of the cool disk mid-plane.

Additional Information

© 2010 American Astronomical Society. Received 2010 July 16; accepted 2010 October 11; published 2010 December 1. We thank the OVRO/CARMA staff and the CARMA observers for their assistance in obtaining the data. We acknowledge support from the Owens Valley Radio Observatory, which is supported by the National Science Foundation through grant AST 05-40399. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology.

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