We present a wide-field CCD photometric study of the Galactic globular cluster NGC 7492. The derived VR color-magnitude diagram (CMD) extends down to about 3.5 mag below the cluster main-sequence turnoff. The field covers 42' × 42', about 3 times larger than the known tidal radius of this cluster. The sample of cluster member candidates obtained by the CMD-mask process has been used to construct luminosity (LFs) and mass functions (MFs) and a surface density map. NGC 7492 has a very flat MF with very little variation in the slope with distance from the cluster center. However, there is a clear evidence for an increase of the MF slope from inner to outer regions, indicating mass segregation of the cluster. The surface density map of NGC 7492 shows extensions toward the Galactic anticenter (northeast) and northwest from the cluster center. A comparison of the LF for stars in the tails with that for stars within the tidal radius suggests that the extensions shown in the surface density map could be a real feature. The overall shape of NGC 7492 is significantly flattened. If the flattened shape of the NGC 7492 is caused by its rotation, the Galactic tidal field must have been an important influence, since the initial rotation would have been almost completely removed by dynamical relaxation.
展开▼
机译：我们介绍了银河系球状星团NGC 7492的宽视场CCD光度研究。派生的VR色度图（CMD）延伸到星团主序列截止以下约3.5 mag。磁场覆盖面积为42'×42'，约为该星团已知潮汐半径的3倍。通过CMD掩膜工艺获得的候选簇成员样本已用于构建亮度（LF）和质量函数（MF）以及表面密度图。 NGC 7492具有非常平坦的MF，其斜率随距群集中心的距离变化很小。但是，有明显的证据表明从内部到外部区域的MF斜率增加，表明该簇的质量偏析。 NGC 7492的表面密度图显示了从星团中心向银河系反中心（东北）和西北方向的扩展。将尾部恒星的LF与潮汐半径以内的恒星的LF进行比较，表明表面密度图中显示的扩展可能是真实的特征。 NGC 7492的整体形状明显变平。如果NGC 7492的扁平形状是由它的旋转引起的，那么银河的潮汐场一定是一个重要的影响因素，因为初始旋转几乎可以通过动力松弛完全消除。
展开▼
