Small-Scale Interstellar Na I Structure toward M92
Small-Scale Interstellar Na I Structure toward M92
复制标题
朝向 M92 的小型星际 Na I 结构
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Lauroesch
中科院分区：
文献类型：
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作者：
S. Andrews;D. Meyer;J. Lauroesch
我们利用KPNO WIYN望远镜上的DensePak光纤阵列的积分场梯形光谱，以4‘的空间分辨率观测了球状星团M92在Na-I-D波长区的中心27“×43”。在LSR速度为0公里的S-1(云1)和-19公里的S-1(云2)的光谱中有两个明显的星际Na-I吸收成分。这两个组件的强度差异很明显，小到受到纤维到纤维分离的限制。得到的NaI柱密度在云1吸收图上相差4倍，在云2图上相差7倍。对于云1和云2，分别使用400pC和800pC的距离上限，吸收图显示了星际介质(ISM)的结构，分辨率分别为1600AU和3200AU。向M92的纤维对纤维的Na I柱密度差异与对球状星团M15的ISM的类似研究中发现的结果相当。总体而言，朝向M92的星际成分中的结构比朝向M15的结构具有明显更低的柱密度。我们将这些低柱密度结构解释为气体中的小尺度湍流变化，并将它们与M15的更大尺度、更高的柱密度变化进行比较，这可能是实际的HI结构的特征。
We have used integral field echelle spectroscopy with the DensePak fiber-optic array on the KPNO WIYN telescope to observe the central 27′′ × 43′′ of the globular cluster M92 in the Na I D wavelength region at a spatial resolution of 4'. Two interstellar Na I absorption components are evident in the spectra at LSR velocities of 0 km s-1 (cloud 1) and -19 km s-1 (cloud 2). Substantial strength variations in both components are apparent down to scales limited by the fiber-to-fiber separations. The derived Na I column densities differ by a factor of 4 across the cloud 1 absorption map and by a factor of 7 across the cloud 2 map. Using distance upper limits of 400 and 800 pc for cloud 1 and cloud 2, respectively, the absorption maps indicate structure in the interstellar medium (ISM) down to scales of 1600 and 3200 AU. The fiber-to-fiber Na I column density differences toward M92 are comparable to those found in a similar study of the ISM toward the globular cluster M15. Overall, the structures in the interstellar components toward M92 have significantly lower column densities than those toward M15. We interpret these low column density structures as small-scale turbulent variations in the gas and compare them with the larger scale, higher column density variations toward M15, which may be the hallmarks of actual H I structures.