Keplerian Circumbinary Disk Candidate in a High-mass Star-forming Region

ABSTRACT :
Accretion disks and bipolar outflows are basic building blocks of high-mass star formation as well as low-mass star formation. The QUARKS survey observed 139 high-mass star-forming clumps in continuum and various lines in the ALMA band 6 at ~0.3” angular resolutions. In this study, we analyzed the QUARKS data of a high-mass star-forming region, IRAS 08303-4303 (2.35 kpc), in order to investigate the disk-outflow systems of high-mass YSOs. By combining data from three ALMA configurations (ACA, C2, C5), we achieved a resolution of ~600 AU and recovered emission scales up to ~0.1 pc. We identified five continuum peaks and at least 4 CO outflows in this region. Two continuum peaks are particularly close (< 1000 AU) and appear to be a protobinary system. The protobinary resides within a single rotating structure that shows a Keplerian-like rotation pattern. We measured the rotation temperature using multiple transitions of both CH3CN and CH3OH, and estimated the mass of this circumbinary disk from the continuum data. We also derived the enclosed mass of the protobinary under the assumption that the circumbinary disk is in Keplerian rotation.