标题： L1521F-IRS和IRAM 04191+1522非常低光度原恒星天体周围的碳链和有机分子 显示英文标题

标题： Carbon-Chain and Organic Molecules around Very Low-Luminosity Protostellar Objects of L1521F-IRS and IRAM 04191+1522

摘要： 我们使用那不勒斯45米射电望远镜在碳链分子和有机分子线中观察到了非常低光度天体（VeLLOs）L1521F-IRS和IRAM 04191+1522周围的致密气体。对于L1521F-IRS，CH3CCH（50-40）、C4H（17/2-15/2）和C3H2（212-101）的碳链线强度比IRAM 04191+1522强1.5至3.5倍，而碳链分子在L1521F-IRS处的丰度比在IRAM 04191+1522处高2至5倍。这些碳链分子线的映射观测显示，在L1521F中，这些碳链分子线的峰值位置彼此不同，并且在VeLLO位置没有发射峰值，而在IRAM 04191+1522中，这些碳链线除了C3H2线外，都弱到接近检测极限。在L1521F和IRAM 04191+1522之间观察到的化学差异表明，L1521F-IRS的演化阶段比IRAM 04191+1522更年轻，这与在13CO（1-0）线中看到的相关喷流范围一致。CH3OH（6-2-7-1 E）和CH3CN（60-50）有机分子线的未检测到表明，由中心原恒星加热的温暖（约100 K）分子脱附区域在L1521F-IRS和IRAM 04191+1522方向上小于约100 AU，这表明这些VeLLOs年龄较小。我们提出，周围致密气体的化学状态可以用来追踪VeLLOs的演化阶段。 显示英文摘要

摘要： We have observed dense gas around the Very Low-Luminosity Ob jects (VeLLOs) L1521F-IRS and IRAM 04191+1522 in carbon-chain and organic molecular lines with the Nobeyama 45 m telescope. Towards L1521F-IRS, carbon-chain lines of CH3CCH (50-40), C4H (17/2-15/2), and C3H2 (212-101) are 1.5 - 3.5 times stronger than those towards IRAM 04191+1522, and the abundances of the carbon-chain molecules towards L1521F-IRS are 2 to 5 times higher than those towards IRAM 04191+1522. Mapping observations of these carbon-chain molecular lines show that in L1521F the peak positions of these carbon-chain molecular lines are different from each other and there is no emission peak towards the VeLLO position, while in IRAM 04191+1522 these carbon-chain lines are as weak as the detection limits except for the C3H2 line. The observed chemical differentiation between L1521F and IRAM 04191+1522 suggests that the evolutionary stage of L1521F-IRS is younger than that of IRAM 04191+1522, consistent with the extent of the associated outflows seen in the 13CO (1-0) line. The non-detection of the organic molecular lines of CH3OH (6-2-7-1 E) and CH3CN (60-50) implies that the warm (~ 100 K) molecular-desorbing region heated by the central protostar is smaller than ~ 100 AU towards L1521F-IRS and IRAM 04191+1522, suggesting the young age of these VeLLOs. We propose that the chemical status of surrounding dense gas can be used to trace the evolutionary stages of VeLLOs.