Spatially resolved H 2 emission from a very low-mass star ,,
Spatially resolved H 2 emission from a very low-mass star ,,
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极低质量恒星的空间分辨 H 2 发射 ,,
DOI：
10.1051/0004-6361/201321110
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发表时间：
2013
影响因子：
6.5
通讯作者：
S. Antoniucci
中科院分区：
文献类型：
--
作者：
R. G. Lopez;A. C. O. Garatti;G. Weigelt;B. Nisini;S. Antoniucci
语境。对极低质量恒星（VLMS）和褐矮星的分子流出的研究很少。到目前为止，仅观察到少量二氧化碳流出，使我们能够绘制紧邻星周环境的地图。目标。我们提出了 IRS54 (YLW 52) 周围的首次空间分辨 H2 发射，IRS54 是~0.1-0.2 MClass I 源。方法。通过 VLT SINFONI K 波段观测，我们探测了距源头 50 个天文单位的 H2 发射。结果。分子发射显示出复杂的结构，描绘出大的流出腔和不对称的分子射流。由于检测到了几个 H2 跃迁，我们能够估计 AV ∼ 28 mag、T ∼ 2000−3000 K 和 H2 柱密度 N(H2) ∼ 1.7 × 10 17 cm -2 的喷射状结构（从源位置到结 D）的平均值。这使我们能够估计热 H2 组分的质量损失率为 ∼2 × 10 -10 Myr -1 。此外，根据Br γ线的总通量，我们推断出吸积光度和质量吸积率分别为0.64L和∼3 × 10 -7 Myr -1 。流出结构与低质量 I 类和 CTTS 中发现的结构相似。然而，Lacc/Lbol 比率非常高（~80%），并且与质量大致相同的物体相比，质量吸积率大约高一个数量级，这表明所研究的源的年轻性质。
Context. Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs have been studied very little. So far, only a few CO outflows have been observed, allowing us to map the immediate circumstellar environment. Aims. We present the first spatially resolved H2 emission around IRS54 (YLW 52), a ∼0.1-0.2 MClass I source. Methods. By means of VLT SINFONI K-band observations, we probed the H2 emission down to the first ∼50 AU from the source. Results. The molecular emission shows a complex structure delineating a large outflow cavity and an asymmetric molecular jet. Thanks to the detection of several H2 transitions, we are able to estimate average values along the jet-like structure (from source position to knot D) of AV ∼ 28 mag, T ∼ 2000−3000 K, and H2 column density N(H2) ∼ 1.7 × 10 17 cm −2 . This allows us to estimate a mass loss rate of ∼2 × 10 −10 Myr −1 for the warm H2 component. In addition, from the total flux of the Br γ line, we infer an accretion luminosity and mass accretion rate of 0.64Land ∼3 × 10 −7 Myr −1 , respectively. The outflow structure is similar to those found in low-mass Class I and CTTS. However, the Lacc/Lbol ratio is very high (∼80%), and the mass accretion rate is about one order of magnitude higher when compared to objects of roughly the same mass, pointing to the young nature of the investigated source.