MILLIMETER-WAVE CONTINUUM MEASUREMENTS OF YOUNG STARS

摘要

New continuum observations at 1.3 mm of 121 young stars are presented; the majority of these objects have not been previously observed. The stars which are detected are interpreted assuming that the emission is thermal radiation from small particles entrained in circumstellar disks. Several new conclusions are drawn. 1. The presence of a companion star clearly affects the millimeter-wave continuum emission and, by implication, the disks. Companions closer than about 100 AU inhibit disk formation. 2. Weak-line and naked T Tauri stars do, in fact, have less millimeter-wave emission than classical T Tauri stars. It appears that the reason is an absence of even cold particles, not simply lower luminosities for an otherwise large reservoir of particles. An equivalent width for Hα of 0.4 nm appears to be a natural dividing line between detected and nondetected sources. 3. Within the uncertainties, there is no difference between the distribution of disk masses in the Cepheus IV association and Taurus-Auriga. 4. With better sensitivity, the distribution of disk masses can be seen to extend down below the approximate limit of 0.01 solar mass determined in the survey of Beckwith et al. (1990).