We have performed mid-IR photometry of the young open cluster NGC 2264 using the images obtained with the Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer instruments and presented a normalized classification scheme of young stellar objects in various color-color diagrams to make full use of the information from multicolor photometry. These results are compared with the classification scheme based on the slope of the spectral energy distribution (SED). From the spatial distributions of Class I and II stars, we have identified two subclusterings of Class I objects in the CONE region of Sung et?al. The disked stars in the other star-forming region S Mon are mostly Class II objects. These three regions show a distinct difference in the fractional distribution of SED slopes as well as the mean value of SED slopes. The fraction of stars with primordial disks is nearly flat between log m = 0.2 and –0.5 and that of transition disks is very high for solar mass stars. In addition, we have derived a somewhat higher value of the primordial disk fraction for NGC 2264 members located below the main pre-main-sequence locus (so-called BMS stars). This result supports the idea that BMS stars are young stars with nearly edge-on disks. We have also found that the fraction of primordial disks is very low near the most massive star S Mon and increases with distance from S Mon.
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机译：我们使用Spitzer空间望远镜红外阵列相机和Spitzer仪器的多波段成像光度计获得的图像，对年轻的开放星团NGC 2264进行了中红外测光，并在各种彩色-彩色图中提出了年轻恒星物体的归一化分类方案，以充分利用多色光度法的信息。将这些结果与基于谱能量分布（SED）斜率的分类方案进行比较。根据I类和II类恒星的空间分布，我们在Sung等人的CONE区域中确定了I类物体的两个子簇。在另一个形成恒星的区域S Mon中的盘状恒星大部分是II类天体。这三个区域在SED斜率的分数分布以及SED斜率的平均值方面显示出明显的差异。在太阳的质量恒星中，具有原始盘的恒星的分数在log m = 0.2和–0.5之间几乎持平，而过渡盘的分数非常高。此外，对于位于主要主序前位点（所谓的BMS星）之下的NGC 2264成员，我们得出了原始盘分数更高的值。这个结果支持了BMS恒星是具有近边缘盘的年轻恒星的想法。我们还发现，在最大质量的恒星S Mon附近，原始盘的比例非常低，并且随着距S Mon的增加而增加。
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