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Published May 10, 2010 | Published
Journal Article Open

Investigating Planet Formation in Circumstellar Disks: CARMA Observations of Ry Tau and Dg Tau


We present CARMA observations of the thermal dust emission from the circumstellar disks around the young stars RY Tau and DG Tau at wavelengths of 1.3 mm and 2.8 mm. The angular resolution of the maps is as high as 0".15, or 20 AU at the distance of the Taurus cloud, which is a factor of 2 higher than has been achieved to date at these wavelengths. The unprecedented detail of the resulting disk images enables us to address three important questions related to the formation of planets. (1) What is the radial distribution of the circumstellar dust? (2) Does the dust emission show any indication of gaps that might signify the presence of (proto-)planets? (3) Do the dust properties depend on the orbital radius? We find that modeling the disk surface density in terms of either a classical power law or the similarity solution for viscous disk evolution reproduces the observations well. Both models constrain the surface density between 15 and 50 AU to within 30% for a given dust opacity. Outside this range, the densities inferred from the two models differ by almost an order of magnitude. The 1.3 mm image from RY Tau shows two peaks separated by 0."2 with a decline in the dust emission toward the stellar position, which is significant at about 2σ-4σ. For both RY Tau and DG Tau, the dust emission at radii larger than 15 AU displays no significant deviation from an unperturbed viscous disk model. In particular, no radial gaps in the dust distribution are detected. Under reasonable assumptions, we exclude the presence of planets more massive than 5 M_J orbiting either star at distances between about 10 and 60 AU, unless such a planet is so young that there has been insufficient time to open a gap in the disk surface density. The radial variation of the dust opacity slope, β, was investigated by comparing the 1.3 mm and 2.8 mm observations. We find mean values of β of 0.5 and 0.7 for DG Tau and RY Tau, respectively. Variations in β are smaller than Δβ = 0.7 between 20 and 70 AU. These results confirm that the circumstellar dust throughout these disks differs significantly from dust in the interstellar medium.

Additional Information

© 2010 The American Astronomical Society. Received 2009 August 12; accepted 2010 March 22; published 2010 April 22. We thank Antonella Natta and referee Steven Beckwith for reading the manuscript and providing helpful suggestions. We thank the OVRO/CARMA staff and the CARMA observers for their assistance in obtaining the data. Support for the Combined Array for Research in Millimeter Astronomy construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the Associates of the California Institute of Technology, the states of California, Illinois, and Maryland, and the National Science Foundation. OngoingCARMAdevelopment and operations are supported by the National Science Foundation under a cooperative agreement (grant AST 08-38260), and by the CARMA partner universities. 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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Published - Isella2010p9983Astrophys_J.pdf


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