A Study of Dense Cloud Cores and Star Formation in Lupus: C18O <i>J</i> = 1−0 Observations with NANTEN

Abstract

We have made an extensive study of dense cloud cores and star formation in the Lupus dark-cloud complex. Millimeter-wave observations in the C18O (J = 1−0) emission at 2.6 mm wavelength were made with the “NANTEN,” a 4-m mm-wave telescope of Nagoya University at Las Campanas Observatory. Thirty-six dense cores were identified and mapped in the C18O emission at 2′ grid spacing with a 2′.7 beam. The typical mass, radius, H2 column density, and line width of the C18O cores are 9.7 M⊙ , 0.17 pc, 4.1 × 1021 cm-2, 0.90 km s-1, respectively. The mass spectrum of the C18O cores was fitted by a single power-law index of γ = −1.7± 0.6 for Mcore ≥ 3 M⊙ . The physical parameters of the dense C18O cores were derived and compared with those in Taurus, Ophiuchus North, and L 1333. The average characteristics of the C18O cores in Lupus are similar to those in Ophiuchus North and L 1333, although those in Taurus are found to be different, especially in the line width, virial ratio, and mass spectrum index among the four regions. By comparing the physical properties of the C18O cores with the distribution of YSOs and H13CO+ condensations in Lupus, we have confirmed a trend suggested in previous studies, that star formation preferentially occurs in cores having a small virial ratio, Mvir/Mcore, and a large H2 column density.