Circumstellar molecular gas of the HH 34 and HH 111 exciting stars

The HH 34 and HH 111 exciting stars, two pre-main-sequence objects which are the sources of highly collimated optical jets, have been observed in the J = 1-0 transition of (C-13)O and in the 2.7 mm continuum using the Owens Valley Radio Observatory Millimeter Interferometer. The high-resolution aperture synthesis maps reveal dense molecular gas concentrations at the positions of both stars. The morphology and kinematics of the bright emission-line cores suggest that the molecular gas is distributed in circumstellar disks, each about 2000 AU in diameter, elongated perpendicular to each system's outflow axis. A fainter component of (C-13)O emission extends along each source's outflow axis. Independent mass determinations based on the dust continuum and molecular line fluxes indicate for HH 34, a disk mass of 0.2 solar mass; and for HH 111, a disk mass of 0.3 solar mass. The inferred circumstellar disks of these two jet sources are significantly more massive than those found associated with T Tauri stars and are therefore among the most massive disks known in association with low-mass pre-main-sequence stars.