基于IRSF/SIRIUS近红外观测的LMC H I脊区的消光和尘埃/气体比
Extinction and dust/gas ratio in the H I ridge region of the LMC based on the IRSF/SIRIUS near-infrared survey
摘要：
利用IRSF的近红外（IR）观测资料，给出了H1脊区大麦云云（LMC）的尘埃消光AV图，并将AV图与CO和H1观测的总氢柱密度N（H）图进行了比较。在大麦哲伦星云的H I脊区，我们发现了两个速度H I分量（外加一个中等速度分量），年轻的大质量星团可能是由它们碰撞形成的。此外，其中一种成分被认为是来自小麦哲伦云（SMC）的流入气体，预计其金属含量更低（Fukui et al. 2017，PASJ，69，L5）。为了详细评估H I脊区域的尘埃/气体比率，我们从最近校准更新的IRSF数据的近红外颜色过量导出AV图，并将所得AV图与不同速度分量的N（H）图的组合进行拟合，以成功地将其分解为3个分量。结果，我们发现组分之间的AV /N（H）相差2倍。此外，CO到H2的转换因子也表明组分之间的差异，暗示金属丰度的差异。我们的研究结果很可能支持的情况下，在LMC H I脊区域的气体被污染的流入气体从SMC的几何形状与正在进行的碰撞之间的两个速度分量。
英文摘要：
We present a dust extinction AV map of the Large Magellanic Cloud (LMC) in the H I ridge region using the IRSF near-infrared (IR) data, and compare the AV map with the total hydrogen column density N(H) maps derived from the CO and H I observations. In the LMC H I ridge region, the two-velocity H I components (plus an intermediate velocity component) are identified, and the young massive star cluster is possibly formed by collision between them. In addition, one of the components is suggested to be an inflow gas from the Small Magellanic Cloud (SMC) which is expected to have even lower metallicity gas (Fukui et al. 2017, PASJ, 69, L5). To evaluate dust/gas ratios in the H I ridge region in detail, we derive the AV map from the near-IR color excess of the IRSF data updated with the latest calibration, and fit the resultant AV map with a combination of the N(H) maps of the different velocity components to successfully decompose it into the 3 components. As a result, we find difference by a factor of 2 in AV /N(H) between the components. In additon, the CO-to-H2 conversion factor also indicates difference between the components, implying the difference in the metallicity. Our results are likely to support the scenario that the gas in the LMC H I ridge region is contaminated with an inflow gas from the SMC with a geometry consistent with the on-going collision between the two velocity components.
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