The Nobeyama millimeter array survey of young stellar objects associated with the Taurus molecular cloud

We have carried out an interferometric survey of 3 mm continuum and CS (J = 2-1) line emissions from 13 optically invisible protostar candidates and six young T Tauri stars associated with the Taurus molecular cloud. The survey was made using the Nobeyama Millimeter Array with a spatial resolution of 2.'' 18-10 ''. The continuum emission was detected from two protostar candidates and five T Tauri stars and was well coincident with optical or infrared objects. It was not spatially resolved and most probably originated from compact circumstellar disks. The CS emission was detected around 11 protostar candidates and two T Tauri stars. The detected CS condensations are extended, with a typical size and mass of similar to 2000 AU and 0.01 M., respectively. Among the eleven protostar candidates with detectable CS emission, seven sources, i.e., IRAS 04016+2610 (L1489), IRAS 04169+2702, IRAS 04191+1503, IRAS 04239+2436, L1551-IRS 5, IRAS 04325+2402, and IRAS 04365+2535, have the CS emission well coincident with infrared sources, while the other four show the CS emission separated away from known infrared sources. Most of the CS emission for the former sources may arise from the innermost part of their protostellar envelopes, while that for the latter sources may originate from compact, dense gas in the vicinity of the infrared sources. The CS gases toward L1489 and IRAS 04365+2535 have disklike structures of similar to 1500 and similar to 500 AU in radius, respectively, with velocity gradients along their major axes. The velocity gradient of the disklike structure around L1489 may be due to rotation, while the origin of velocity gradient around IRAS 04365+2535 is not clear. L1551-IRS 5 shows compact CS emission, possibly arising from a disk, together with weak extended features that may be attributed to a denser part of the outflow. The distribution of CS emission around IRAS 04368+2557 (L1527) is anticorrelated with its molecular outflow, suggesting that the CS gas may be a dense shell swept up by the outflow. The 3 mm continuum detectability toward the protostar candidates is significantly smaller than what we would expect from the statistics of T Tauri disks, which we consider may be due to an evolutionary effect; namely, during the transitional phase from embedded protostars to revealed T Tauri stars, either the disk mass has rapidly increased, or dust particles in the disks have grown significantly, or both. For the embedded protostar candidates, the CS intensity is correlated with bolometric luminosity. This may mean that the final stellar mass is correlated with the mass of dense cores.