Star count analysis of the interstellar matter in the region of L1251
Star count analysis of the interstellar matter in the region of L1251
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DOI：
10.1051/0004-6361:20047059
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发表时间：
2004-08
影响因子：
6.5
通讯作者：
L. G. Bal'azs;P. 'Abrah'am;M. Kun;J. Kelemen;L. Observatory;M. Astronomie;Eotvos Univ.
中科院分区：
文献类型：
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作者：
L. G. Bal'azs;P. 'Abrah'am;M. Kun;J. Kelemen;L. Observatory;M. Astronomie;Eotvos Univ.
利用光学星星计数研究了形成云L1251的星星内部和周围的ISM分布。用基于最大似然的统计方法进行了仔细的计算，从星星计数图中得到了B、V、R、I消光分布。得出的距离为330 ± 30 pc。灭绝图显示了一个细长的密集云，在其东侧有弓形激波。我们估计弓形激波的马赫数为M/2。探测到了一个明显的尘埃性质的变化，即RV = AV /EB−V总消光比与选择消光比在3到5.5之间变化，峰值出现在L1251的非对称部分。L1251头部的空间结构用Schuster球（即n = 5多变球）很好地建模。观测到的质量径向分布与模型的拟合精度很高，距离假定中心2.5 pc。出乎意料的是，NH3 1.3厘米线宽的分布也很好地匹配舒斯特解决方案，即使在云的尾部。由于L1251的细长头尾结构远离球对称，尾部线宽的良好拟合使得可以合理地假设目前的云结构是由等温收缩形成的。
We studied the ISM distribution in and around the star forming cloud L1251 with optical star counts. A careful calculation with a maximum likelihood based statistical approach resulted in B, V, R, I extinction distributions from the star count maps. A distance of 330 ± 30 pc was derived. The extinction maps revealed an elongated dense cloud with a bow shock at its eastern side. We estimated a Mach number of M ≈ 2 for the bow shock. A variation of the apparent dust properties is detected, i.e. the RV = AV /EB−V total to selective extinction ratio varies from 3 to 5.5, peaking at the densest part of L1251. The spatial structure of the head of L1251 is well modelled with a Schuster-sphere (i.e. n = 5 polytropic sphere). The observed radial distribution of mass fits the model with high accuracy out to 2.5 pc distance from the assumed center. Unexpectedly, the distribution of NH3 1.3 cm line widths is also well matched by the Schuster solution even in the tail of the cloud. Since the elongated head-tail structure of L1251 is far from the spherical symmetry the good fit of the linewidths in the tail makes it reasonable to assume that the present cloud structure has been formed by isothermal contraction.