13CO (J= 1-0) observations of the Lupus molecular clouds

Abstract

Large-scale 13CO (J = 1-0) observations were carried out toward the Lupus region using the new 4-m millimeter-wave telescope at Nagoya University (HPBW = 2′.7). Four molecular clouds (Lupus 1, 2, and 3 and a newly found cloud) were mapped using an 8′ grid spacing. The masses of the four clouds were estimated to be 1200, 100, 300, and 1000 M(Fish eye sign), respectively. Around an infrared point source, IRAS 15398-3359. associated with Lupus 1, we discovered a CO molecular outflow with a relatively short dynamical time scale of ~ 2000 yr, which indicates ongoing star formation in the Lupus region. Including the outflow source, about 50 candidates for young stellar objects can be found in the literature, which are apparently associated with 13CO clouds. Comparing these objects with our 13CO data, we find that the star-formation efficiency of the four clouds varies over a wide range from 0.4 to ≥ 3.8%, which might represent their different stages of star formation, or might be due to a difference in the interaction with the nearby Scorpius HI shell.