Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C7H in Molecular Clouds
Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C7H in Molecular Clouds
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DOI：
10.3847/1538-4357/aa8637
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发表时间：
2017-09-20
影响因子：
4.9
通讯作者：
Tsukiyama, Koichi
中科院分区：
文献类型：
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作者：
Araki, Mitsunori;Takano, Shuro;Tsukiyama, Koichi
利用100米绿岸望远镜，在低质量恒星形成区L1527寻找长碳链分子，这是一个典型的暖碳链化学（WCCC）来源。检测到长碳链分子C7H (（2)Pi(1/2)）、C6H ((2)Pi（3/2）和(2)Pi（1/2）、CH3C4H和C6H2 (cumulene carbene, CCCCCCH2)，以及C3H和C3H2O的环态。特别是C7H首次在分子云中被检测到。测定C7H柱密度为6 × 10(10) cm（-2）。L1527中碳链分子（包括CH3C4H和C6H）的柱密度相对于无星暗云中金牛座分子云（Taurus Molecular cloud -1 Cyanopolyyne Peak, TMC-1 CP）中碳链长度越长，柱密度越低。然而，C7H和C6H2的柱密度不遵循这一趋势，在L1527中相对丰富。这个结果表明，这些长碳链分子是冷无星阶段的残余物。l1527的残余和WCCC产物都被观测到，这一结果与原恒星也可能在化学演化的相对早期阶段诞生于母核的观点一致。
Long carbon-chain molecules were searched for toward the low-mass star-forming region L1527, which is a prototypical source of warm carbon-chain chemistry (WCCC), using the 100 m Green Bank Telescope. Long carbon-chain molecules, C7H ((2)Pi(1/2)), C6H ((2)Pi(3/2) and (2)Pi(1/2)), CH3C4H, and C6H2 (cumulene carbene, CCCCCCH2), and cyclic species of C3H and C3H2O were detected. In particular, C7H was detected for the first time in molecular clouds. The column density of C7H is determined to be 6 x 10(10) cm(-2). The column densities of the carbon-chain molecules including CH3C4H and C6H in L1527 relative to those in the starless dark cloud Taurus Molecular Cloud-1 Cyanopolyyne Peak (TMC-1 CP) tend to be systematically lower for long carbon-chain lengths. However, the column densities of C7H and C6H2 do not follow this trend and are found to be relatively abundant in L1527. This result implies that these long carbon-chain molecules are remnants of the cold starless phase. The results-that both the remnants and WCCC products are observed toward L1527-are consistent with the suggestion that the protostar can also be born in the parent core at a relatively early stage in the chemical evolution.