Discovery of giant dense molecular gaseous bar in the southern galaxy NGC 986

2007-06-22

ASTE has been used to obtain a CO(3-2) image of NGC 986, a southern starburst galaxy with a large (~14 kpc in length) stellar bar. We found that the stellar bar of NGC 986 is filled with a moderately dense molecular medium. Because inter stellar medium (ISM) in the bar will lose their angular momentum through the bar shock and funneled into the central regions quickly (~ dynamical time scale of the galactic rotation), the discovery of this large gaseous bar is indeed a surprise. A good spatial correlation between dense gas traced by CO(3-2) and Hα can be seen (bottom right). (Kohno et al., 2008, PASJ, in press)

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Distribution of Highly-excited Gas in the Central Molecular Zone of Our Galaxy

Figure: Spatial distributions of molecular gas (upper) and highly-excited gas (lower) in the CMZ of our Galaxy.

2007-06-22

The Central Molecular Zone (CMZ) of our Galaxy, a region of radius $\sim 200$ pc, contains large amount of dense molecular gas with high temperature and a peculiar chemical composition. Using ASTE, T. Oka (Univ. of Tokyo) and colleagues found three spatially extended areas and a number of compact spots of highly excited gas. Many of them show signs of shockwave passage indicating that they may have been heated and accelerated by supernova blastwaves. This suggests that the anomalous physical conditions and peculiar chemical compostion in the CMZ may be originated by a series of supernova explosions, which are legacies of active star formation in the recent past (Oka, Nagai, Kamegai, & Tanaka, PASJ, 59, 15).

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ASTE Observations of Protostellar Envelopes in Submillimeter Molecular Lines

Figure: Results of submillimeter HCN (4-3) and CS (7-6) observations of the protostellar envelope around L483.

2007-06-22

With the new submillimeter telescope, ASTE, we have made observations of protostellar envelopes in submillimeter molecular lines. We found that warm (> 40 K) gas in protostellar envelopes exhibits more extended (> 2000 AU) distribution than expected, and shows different velocity structure from that in cold (~ 10 K) molecular gas. These submillimeter studies of protostellar envelopes could alter our present picture of star formation (Takakuwa et al. 2007, PASJ, 59, 1). Figure shows results of submillimeter HCN (4-3) and CS (7-6) observations of the protostellar envelope around L483. The submillimeter molecular emissions, which trace warmer (> 40 K) molecular gas selectively,exhibit extended (> 2000 AU) distribution, and shows an opposite velocity structure to that of the associated outflow (red and blue arrows).

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