Observations of 11 protostellar sources in Taurus with Nobeyama millimeter array - Growth of circumstellar disks

Abstract

Results are presented of observations of the CS(J = 2-1) line and 98-GHz continua of 11 protostellar IRAS sources made with high spatial resolution of 2.8-8.8 arcsec using the Nobeyama millimeter array (NMA). Spatially extended CS emission is detected around all the embedded sources and the two T Tauri stars DG Tau and HL Tau, while four T Tauri stars and one embedded source L1551-IRS5 have detectable 98 GHz continuum emission from unresolved circumstellar disks of 0.1 solar mass. It is inferred from the tendency of continuum emission to be detected mainly toward the T Tauri stars and CM emission to be detected toward the embedded sources among the observed sources that the T Tauri stars have circumstellar mass distribution more concentrated as disks compared to the embedded sources. Estimation of the mass accretion rate onto such disks indicates that for embedded sources with average luminosity, a significant amount of matter must be accreted onto the disks not only in the embedded phase but also in the very early T Tauri phase.