2014ApJ...790...55F

A fundamental question about the early evolution of low-mass protostars is when circumstellar disks may form. High angular resolution observations of molecular transitions in the (sub)millimeter wavelength windows make it possible to investigate the kinematics of the gas around newly formed stars, for example, to identify the presence of rotation and infall. IRAS 16293-2422 was observed with the extended Submillimeter Array (eSMA) resulting in subarcsecond resolution (0.''46x0.''29, i.e., ∼55x35 AU) images of compact emission from the C¹⁷O (3-2) and C³⁴S (7-6) transitions at 337 GHz (0.89 mm). To recover the more extended emission we have combined the eSMA data with SMA observations of the same molecules. The emission of C¹⁷O (3-2) and C³⁴S (7-6) both show a velocity gradient oriented along a northeast-southwest direction with respect to the continuum marking the location of one of the components of the binary, IRAS 16293A. Our combined eSMA and SMA observations show that the velocity field on the 50-400 AU scales is consistent with a rotating structure. It cannot be explained by simple Keplerian rotation around a single point mass but rather needs to take into account the enclosed envelope mass at the radii where the observed lines are excited. We suggest that IRAS 16293-2422 could be among the best candidates to observe a pseudo-disk with future high angular resolution observations.