1-4 Micron Spectrophotometry of Dust in the Taurus Dark Cloud: Water Ice Distribution in Heiles Cloud 2
1-4 Micron Spectrophotometry of Dust in the Taurus Dark Cloud: Water Ice Distribution in Heiles Cloud 2
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金牛座暗云中尘埃的1-4微米分光光度测量：海尔斯云2中的水冰分布
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发表时间：
2000
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通讯作者：
T. Nagata
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作者：
K. Murakawa;M. Tamura;T. Nagata
我们对金牛座分子云复合体中的61颗海尔斯云2的背景恒星进行了近红外光谱分析。我们使用低色散光谱仪PASP 2，它可以同时获得波长覆盖范围在1.3和4.2 μm之间的光谱。对61个天体中的56个，估算了λ = 3.1 μm处的视消光（AV）和水冰光学厚度（τICE）：对56个天体中的50个，仅根据我们的数据进行了系统估算。为了研究Heiles云2中的水冰分布，我们构造了一张“水冰图”，在图中每个物体的位置都标绘了τICE。然后将水冰图与由Sunada & Kitamura进行的毫米观测获得的C18 O（J = 1-0）图进行比较。我们发现水冰的分布与C_（18）O的分布密切相关。强的水冰吸收被认为是只有向密集的C18 O团块，而较少的水冰吸收被检测到向云的外部区域。正如先前的观测所建议的那样，有一个用于正冰探测的AV阈值（AV 0），但具有显著的分散性; AV 0 = 2-5 mag.分散性可能是由云的内部含水部分沿视线沿着的不同贡献引起的。τICE值随AV的增加而增加，ΔτICE/ΔAV的斜率为0.067，与Taurus分子云的观测值一致。
We have conducted near infrared spectroscopy of 61 background stars toward Heiles Cloud 2 in the Taurus molecular cloud complex. We used a low-dispersion spectrometer, PASP2, which can simultaneously obtain the spectrum with a wavelength coverage between 1.3 and 4.2 μm. For 56 of 61 objects, the visual extinction (AV) and the optical depth of water ice at λ = 3.1 μm (τICE) have been estimated: for 50 of 56 objects, these were systematically estimated from our data only. In order to investigate the water ice distribution in Heiles Cloud 2, we have constructed a "water ice map" in which τICE is plotted at the position of each object. The water ice map is then compared with the C18O (J = 1-0) map obtained by millimeter observations performed by Sunada & Kitamura. We find that the distribution of water ice is closely correlated with that of C18O. Strong water ice absorption is seen only toward the dense C18O clumps, while less water ice absorption is detected toward the outer region of the cloud. There is an AV threshold for the positive ice detection (AV0), as suggested by previous observations, but with a significant scatter; AV0 = 2-5 mag. The scatter might be caused by the different contribution of the inner water-containing portion of the cloud along the line of sight. The value of τICE increases with increasing of AV and the slope of ΔτICE/ΔAV is 0.067, consistent with the previously observed values for the Taurus molecular cloud.