A HIGH-RESOLUTION STUDY OF GAS AND DUST AROUND YOUNG INTERMEDIATE-MASS STARS - EVIDENCE FOR CIRCUMSTELLAR DISKS IN HERBIG AE SYSTEMS

As part of a long-term program of observations to search for and chara cterize disks of gas and dust around intermediate-mass counterparts to solar-mass T Tauri stars, we have probed the environments of seven pr e-main-sequence stars of spectral type Ae using millimeter-wave contin uum and molecular line aperture synthesis imaging. In each case we ide ntify a compact region of thermal continuum emission centered on the s tar. Upper limits to radii are in the range 200-300 AU for five member s of our sample, and 680 AU for the distant source HD 245185. We ident ify an elongated continuum source around HD 163296, with a semimajor a xis of 110 AU. Adopting relatively high values for dust grain opacitie s, we obtain minimum masses of circumstellar dust and gas in the range 0.005-0.034 M-circle dot for the seven sources, assuming that the obs erved continuum emission is optically thin. We detect molecular line e mission from gas regions centered on four of the stars. Two of these r egions are spatially resolved and are found to be elongated, with semi major axes of 310 and 450 AU for HD 163296 and AB Aur, respectively. O rdered velocity gradients along the major axes of both of these struct ures point strongly to the presence of orbiting material in disklike c onfigurations, and we argue that the nebular environments of our entir e sample include substantial disk components.