The Second Survey of the Molecular Clouds in the Large Magellanic Cloud by NANTEN. I. Catalog of Molecular Clouds

Abstract

The second survey of the molecular clouds in the Large Magellanic Cloud in 12 CO ( J = 1–0) was carried out by NANTEN. The sensitivity of this survey is twice as high as that of the previous NANTEN survey, leading to a detection of molecular clouds with M CO ≳ 2 × 10 4 M ☉ . We identified 272 molecular clouds, 230 of which are detected at three or more observed positions. We derived the physical properties, such as size, line width, and virial mass, of the 164 GMCs that have an extent more than the beam size of NANTEN in both the major and minor axes. The CO luminosity and virial mass of the clouds show a good correlation of M vir ∝ L CO 1.1 ± 0.1 , with a Spearman rank correlation of 0.8, suggesting that the clouds are in nearly virial equilibrium. Assuming the clouds are in virial equilibrium, we derived an X CO -factor of ~7 × 10 20 cm −2 (K km s −1 ) −1 . The mass spectrum of the clouds is fitted well by a power law of N cloud (> M CO ) ∝ M CO −0.75 ± 0.06 above the completeness limit of 5 × 10 4 M ☉ . The slope of the mass spectrum becomes steeper if we fit only the massive clouds, e.g., N cloud (> M CO ) ∝ M CO −1.2 ± 0.2 for M CO ⩾ 3 × 10 5 M ☉ .