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In order to precisely determine the temperature and density of molecular gas in the Large Magellanic Cloud, we made observations of the optically thin 13 CO(J = 3-2) transition using the ASTE 10 m telescope toward nine peaks where 12 CO(J = 3-2) clumps were previously detected with the same telescope. The molecular clumps include those in giant molecular cloud (GMC) Types I (with no signs of massive star formation), II (with H ii regions only), and III (with H ii regions and young star clusters). We detected 13 CO(J = 3-2) emission toward all the peaks and found that their intensities are 3-12 times lower than those of 12 CO(J = 3-2). We determined the intensity ratios of 12 CO(J = 3-2) to 13 CO(J = 3-2), R 12/13 3-2 , and 13 CO(J = 3-2) to 13 CO(J = 1-0), R 13 3-2/1-0 , at 45 resolution. These ratios were used in radiative transfer calculations in order to estimate the temperature and density of the clumps. The clumps have a kinetic temperature range of T kin = 15-200 K and a molecular hydrogen gas density range of n(H 2 ) = 8 × 10 2 -7 × 10 3 cm −3 . We confirmed that the higher density clumps have higher kinetic temperature and that the lower density clumps have lower kinetic temperature to better accuracy than in previous work. The kinetic temperature and density increase generally from a Type I GMC to a Type III GMC. We interpret that this difference reflects an evolutionary trend of star formation in molecular clumps. The R 13 3-2/1-0 and kinetic temperature of the clumps are well correlated with the Hα flux, suggesting that the heating of molecular gas with density n(H 2 ) = 10 3 -10 4 cm −3 can be explained by stellar far-ultravoilet photons.

We report on a plan to construct a 50-m-class single-dish telescope, the Large Submillimeter Telescope (LST). The conceptual design and key science behind the LST are presented, together with its tentative specifications. This telescope is optimized for wide-area imaging and spectroscopic surveys in the 70-420 GHz frequency range, which spans the main atmospheric windows at millimeter and submillimeter wavelengths for good observation sites such as the Atacama Large Millimeter/submillimeter Array (ALMA) site in Chile. We also target observations at higher frequencies of up to 1 THz, using an inner high-precision surface. Active surface control is required in order to correct gravitational and thermal deformations of the surface, and will be useful for correction of the wind-load deformation. The LST will facilitate new discovery spaces such as wide-field imaging with both continuum and spectral lines, along with new developments for time-domain science. Through exploitation of its synergy with ALMA and other telescopes, the LST will contribute to research on a wide range of topics in the fields of astronomy and astrophysics, e.g., astrochemistry, star formation in our Galaxy and galaxies, the evolution of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect, the search for transients such as γ-ray burst reverse shocks produced during the epoch of re-ionization, electromagnetic follow up of detected gravitational wave sources, and examination of general relativity in the vicinity of super massive black holes via submillimeter very-long-baseline interferometry (VLBI).

The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10-m telescope. This survey covered 4.5 deg 2 of the SMC with 1σ noise levels of 5-12 mJy beam −1 , and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 µm, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. The 1.1 mm objects show dust temperatures of 17-45 K and gas masses of 4 × 10 3 -3 × 10 5 M ⊙ , assuming single-temperature thermal emission from the cold dust with an emissivity index, β, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 µm and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 µm flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.