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| EPoS Contribution |
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Chemical Diversity of Low-Mass Star Forming Regions; Peculiar Compositions in L1527 and IRAS15398-3359
Nami Sakai Department of Physics, The University of Tokyo, Tokyo, Japan | |
| We have found low-mass star forming-regions which show extremely high abundances of carbon-chain molecules. Those are L1527 in Taurus and IRAS15398-3359 in Lupus (e.g. Sakai et al. 2008a; 2009a). In L1527, the line broadening is observed toward the protostar, indicating that carbon-chain molecules exist even in the gas infalling to the protostar. On the other hand, high excitation lines of CCH show central condensation around the protostar, IRAS15398-3359. In these sources, carbon-chain molecules would be regenerated in a lukewarm region near the protostar, triggered by the evaporation of the CH$_4$ ice. This is new carbon-chain chemistry (Warm Carbon-Chain Chemistry: WCCC) in contrast to the conventional one which has long been applied to cold starless cores. The discovery of the WCCC sources demonstrates that the chemical composition of low-mass star-forming regions is not uniform, but has a significant variety. In particular, a remarkable contrast can be seen between WCCC and hot corino chemistry. Carbon-chain molecules are deficient in hot corino sources like NGC1333IRAS4B, whereas complex organic molecules seem to be less abundant in the WCCC sources. A possible origin for this would be the time scale of the starless-core phase; a shorter contraction time would result in WCCC. Relatively low deuterium fractionation ratios in L1527 also support this scenario. Thus, the chemical composition provides an important clue to explore the source-to-source variation of star-formation processes, which will be a good target for ALMA. | |
| Collaborators: Tatsuya Shiino, The Univ. of Tokyo, Japan Takeshi Sakai, The Univ. of Tokyo, Japan Tomoya Hirota, NAOJ, Japan Satoshi Yamamoto, The Univ. of Tokyo, Japan |
Key publication
Suggested Session: Chemistry, Cores and Collapse |