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arXiv 1109.6151astro-ph.SR
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银河系年轻星团Be 59的宽带光学偏振研究

Broad-band Optical Polarimetric Studies toward the Galactic young star cluster Be 59

C. Eswaraiah, A. K. Pandey, G. Maheswar, W. P. Chen, D. K. Ojha, H. C. Chandola

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22 pages, 14 figures and 7 tables, Accepted in MNRAS
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摘要：

我们提出了多波长光学线性偏振观测的69颗恒星对年轻的疏散星团Be 59。观测结果表明，在距离\sim 300、\sim 500和\sim 700 pc处存在三个尘埃层。尘埃层产生的总偏振Pv \sim为5.5%。由于尘埃层的偏振和偏振角的平均值被发现随距离系统地增加。我们表明，结合（U-B）-（B-V）的颜色-颜色图的旋光产生了更好的识别集群成员。偏振测量表明，由于团簇内介质的偏振度为\sim 2.2%，团簇区域存在反常的红化规律，表明其晶粒尺寸比扩散ISM中的晶粒尺寸相对较大。发现极化和E（B-V）的空间变化随着距团簇中心的径向距离的增加而增加，而θv和λmax随着距团簇中心的径向距离的增加而减小。大约40%的星团成员在偏振角上显示出内禀偏振或旋转的特征。有迹象表明，由于前景尘埃层和星团内部介质中尘埃颗粒的不均匀排列，星团成员的星光可能已经被消偏振。

英文摘要：

We present multiwavelength optical linear polarimetric observations of 69 stars toward the young open cluster Be 59. The observations reveal the presence of three dust layers located at the distances of \sim300, \sim500 and \sim700 pc. The dust layers produce a total polarization Pv \sim 5.5 per cent. The mean values of polarization and polarization angles due to the dust layers are found to increase systematically with distance. We show that polarimetry in combination with the (U - B) - (B - V) colour-colour diagram yields a better identification of cluster members. The polarization measurements suggest that the polarization due the intra-cluster medium is \sim 2.2 per cent. An anomalous reddening law exists for the cluster region, indicating a relatively larger grain size than that in the diffuse ISM. The spatial variation of the polarization and E(B - V) is found to increase with radial distance from the cluster center, whereas the θv and λmax are found to decrease with increasing radial distance from the cluster center. About 40 per cent of cluster members show the signatures of either intrinsic polarization or rotation in their polarization angles. There is an indication that the star light of the cluster members might have been depolarized because of non-uniform alignment of dust grains in the foreground dust layers and in the intra-cluster medium.

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