Global survey of star clusters in the Milky Way - I. The pipeline and fundamental parameters in the second quadrant
Global survey of star clusters in the Milky Way - I. The pipeline and fundamental parameters in the second quadrant
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DOI：
10.1051/0004-6361/201118708
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发表时间：
2012-07
影响因子：
6.5
通讯作者：
N. Kharchenko;A. Piskunov;A. Piskunov;E. Schilbach;S. Röser;Ralf-Dieter Scholz
中科院分区：
文献类型：
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作者：
N. Kharchenko;A. Piskunov;A. Piskunov;E. Schilbach;S. Röser;Ralf-Dieter Scholz
目标。在PPMXL星表的基础上，我们对银河系第二象限的星团进行了调查。方法。从PPMXL的位置和固有运动目录中，我们从2MASS中提取了近红外光度测量的恒星子集，并添加了剩余的2MASS无固有运动的恒星（称为2MAst，即具有天体测量的2MASS）。我们开发了一个数据处理管道，包括对一组标准化多维图的交互式人工控制，以确定星团区域内恒星的运动学和光度隶属概率。该管道同时产生了一个星团的天体物理参数。从文献中，我们编制了目前已知的开放星团和球状星团、候选星团、关联星团和移动星团的目标列表。从已确定的成员星中，我们得到了空间参数（星团主要形态部分的中心坐标和半径）和星团运动学（平均固有运动，有时径向速度）。对于距离、变红和年龄的确定，我们使用了特定的理论等时线。潮汐参数通过三参数King剖面与观测到的成员密度分布的拟合得到。结果。我们研究了银河系第二象限的所有871个天体，其中我们成功地研究了642个疏散星团，2个球状星团和8个恒星协会。剩下的219个天体（24%）被我们识别为不存在的星团，重复的条目，或者对2MAst来说太暗的星团。我们发现我们的样本在第二象限的距离为2 kpc的地方是完整的，其中平均表面密度为每kpc 2 94个簇。与文献值比较，我们发现在空间和运动学数据，以及光学距离和变红方面有很好的一致性。在年龄测定中发现了小但系统的偏移。
Aims. On the basis of the PPMXL star catalogue we performed a survey of star clusters in the second quadrant of the Milky Way. Methods. From the PPMXL catalogue of positions and proper motions we took the subset of stars with near-infrared photometry from 2MASS and added the remaining 2MASS stars without proper motions (called 2MAst, i.e. 2MASS with astrometry). We developed a data-processing pipeline including interactive human control of a standardised set of multi-dimensional diagrams to determine kinematic and photometric membership probabilities for stars in a cluster region. The pipeline simultaneously produced the astrophysical parameters of a cluster. From literature we compiled a target list of presently known open and globular clusters, cluster candidates, associations, and moving groups. From established member stars we derived spatial parameters (coordinates of centres and radii of the main morphological parts of clusters) and cluster kinematics (average proper motions and sometimes radial velocities). For distance, reddening, and age determination we used specific sets of theoretical isochrones. Tidal parameters were obtained by a fit of three-parameter King profiles to the observed density distributions of members. Results. We investigated all 871 objects in the 2nd Galactic quadrant, of which we successfully treated 642 open clusters, 2 globular clusters, and 8 stellar associations. The remaining 219 objects (24%) were recognised by us to be nonexistent clusters, duplicate entries, or clusters too faint for 2MAst. We found that our sample is complete in the 2nd quadrant up to a distance of 2 kpc, where the average surface density is 94 clusters per kpc 2 . Compared with literature values we found good agreement in spatial and kinematic data, as well as for optical distances and reddening. Small, but systematic offsets were detected in the age determination.