A new survey of the LMC has been completed in 2.6 mm carbon monoxide emission with NANTEN. This survey has revealed 107 giant molecular clouds, the first complete sample of giant molecular clouds in a single galaxy at a linear resolution of ∼ 40 pc. The cloud mass ranges from ∼ 6 × 104 to 2 × 106 M⊙, and the total molecular mass has been estimated to be 4–7 × 107 M⊙ for a molecular column density of ≳ 1.0 × 1021 cm-2, corresponding to 5–10% of the atomic mass. The molecular clouds exhibit a good spatial correlation with the youngest stellar clusters whose ages are ≲ 10 Myr, demonstrating that cluster formation is on-going in these clouds. On the other hand, they show little correlation with older clusters or with supernova remnants, suggesting that the molecular clouds are being rapidly dissipated in a several Myrs, probably due to the UV photons of massive stars in clusters.

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We carried out a 12CO survey of molecular clouds in the region of the reflection nebula IC 2118. Our observations covered the whole area of IC 2118 ($\sim 6 \,\mathrm{deg^2}$) with a 2.$^{\prime}$6 beam at a $4^{\prime}$ grid spacing. We identified six molecular clouds. Based on a literature search we found a distance value of 210 pc for the reflection nebula and its associated molecular clouds, indicating that the clouds are probably interacting with the Orion–Eridanus Bubble. Using this distance value, we determined the physical properties of the clouds. We also made an objective prism search for $\mathrm{H}\alpha$ emission stars in the region in order to find possible solar-type stars born in the clouds, and identified 46 candidate pre-main-sequence stars. Their spectroscopic follow-up is in progress. Seven of them have so far proved to be T Tauri stars.

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A survey for high Galactic latitude molecular clouds was carried out toward the far-infrared-excess clouds of Reach et al. (1998, AAA 070.131.207) using the NANTEN telescope. All 68 infrared-excess clouds that are observable from NANTEN were mapped in the $J = 1 \hbox{--} 0$ line of 12CO. CO emission was detected from 32 infrared excess clouds, corresponding to a CO detection rate of 47%. Most of these CO clouds were identified and mapped as high-latitude clouds for the first time. The CO detection rate for the cold ($T_\mathrm{dust} \lt 17 \,\mathrm{K}$) infrared excess clouds is 72%, which is more than a factor of two higher than that of warmer ones, 33%. This indicates that the cold clouds are well shielded from external UV radiation, resulting in a high CO abundance and a low temperature of the clouds. The infrared-excess clouds with no CO emission are most likely to be molecular hydrogen clouds because the temperature is similar to, or lower than, that of the surrounding H i gas. The molecular gas without CO emission seems to occupy more than 90% of the area of the infrared-excess clouds.