A New Intermediate-Mass Protostar in the Cepheus A HW2 Region
A New Intermediate-Mass Protostar in the Cepheus A HW2 Region
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仙王座 A HW2 区域中一颗新的中等质量原恒星
DOI：
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发表时间：
2005
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影响因子：
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通讯作者：
C. Thum
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文献类型：
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作者：
J. Martín;I. Jímenez;A. Rodríguez;S. Martín;C. Thum
我们提出的第一个分子热核心的发现与一个中等质量的原恒星在Cep A HW 2地区。热凝聚检测从单盘和干涉观测的几个高激发旋转线（从100至880 K以上的基态）的SO2在地面振动状态和HC 3 N的振动激发态V7 = 1和V7 = 2。两种分子的动力学温度均为~160 K。SO2 J = 287，21 → 296，24线（基态以上488 K）的高角分辨率观测（1.“25 × 0.”99）表明，热气体集中在一个大小约为0.“6（约430 Au）的致密凝聚体中，位于射电喷流HW 2以东0.”4（300 Au）处。热冷凝中的总SO2柱密度为~1018 cm-2，H2柱密度范围为~1023至6 × 1024 cm-2。H2密度和SO2丰度分别必须大于10 - 7 cm-3和2 × 10-7。最有可能的替代品的性质的热和非常密集的冷凝进行了讨论。从热气体的大柱密度，HC 3 N振动激发线的检测，和大的SO2丰度，我们赞成的解释，一个热的核心加热的中等质量的原恒星的103升。这表明Cep A HW 2区域包含一个非常年轻的恒星群。
We present the discovery of the first molecular hot core associated with an intermediate-mass protostar in the Cep A HW2 region. The hot condensation was detected from single-dish and interferometric observations of several high-excitation rotational lines (from 100 to 880 K above the ground state) of SO2 in the ground vibrational state and of HC3N in the vibrationally excited states v7 = 1 and v7 = 2. The kinetic temperature derived from both molecules is ~160 K. The high angular resolution observations (1.″25 × 0.″99) of the SO2 J = 287, 21 → 296, 24 line (488 K above the ground state) show that the hot gas is concentrated in a compact condensation with a size of ~0.″6 (~430 AU), located 0.″4 (300 AU) east from the radio jet HW2. The total SO2 column density in the hot condensation is ~1018 cm-2, with an H2 column density ranging from ~1023 to 6 × 1024 cm-2. The H2 density and the SO2 fractional abundance must be larger than 107 cm-3 and 2 × 10-7, respectively. The most likely alternatives for the nature of the hot and very dense condensation are discussed. From the large column densities of hot gas, the detection of the HC3N vibrationally excited lines, and the large SO2 abundance, we favor the interpretation of a hot core heated by an intermediate-mass protostar of 103 L☉. This indicates that the Cep A HW2 region contains a cluster of very young stars.