Abstract
?????Radio and optical observations have been made in order to examine star formation in the dark cloud L1333 [?(1950) = 2h210, ?(1950) = 75?15']. A study of the cumulative distribution of field star distance moduli yields a distance value close to 180 pc for the L1333 molecular cloud. 13CO observations revealed two filamentary molecular clouds with distinct velocities of VLSR ~ -2 and 3 km s-1, respectively. Thirteen C18O cores, characterized by an average molecular mass (MLTE) of ~9 M? and a mean density of ~1.4 ? 104 cm-3, are embedded in the two 13CO clouds. We have detected 18 H? emission-line stars projected within or near the 13CO clouds on objective-prism plates. They can be regarded as candidate pre?main-sequence stars formed in the clouds. Five IRAS sources with flux density distributions characteristic of young stellar objects (YSOs) are found in the area of the cloud. Three of the IRAS sources coincide with H? emission-line stars, the others with faint stars without detected H? emission. One of the latter sources is associated with a C18O core and exhibits a protostar-type infrared spectrum. The IRAS source exhibits a winglike feature of ~1.6 km s-1 (full width at zero intensity) in C18O, which may indicate that the YSO has an outflow. We note that the C18O core has the smallest ratio of virial mass (Mvir) to MLTE among the C18O cores in L1333, suggesting that star formation occurs preferentially in a core whose internal kinetic energy is low compared with the self-gravitational energy. A possible scenario for the past star formation activity is discussed.
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