VJK测光系统的基准恒星星族序列
Fiducial Stellar Population Sequences for the VJKs Photometric System
摘要：
我们利用加拿大-法国-夏威夷望远镜上的WIRCam宽视场成像仪获得了7个银河系星团（M92，M15，M13，M5，NGC 1851，M71和NGC 6791）的宽波段近红外测光，并辅以VLT上的HAWK-I拍摄的NGC 1851图像。此外，还将[Fe/H] ~ 0.0疏散星团M67的2 MASS观测数据加入到星团数据库中。从得到的（V-J）-V和（V-Ks）-V色星等图（CMD）中，已经定义了跨越金属丰度范围（-2.4 < [Fe/H] <+0.3）的基准序列，该序列从红巨星分支（RGB）的尖端延伸（对于大多数星团）到主序列关闭点以下约2.5个星等。这些基准点为解释2 MASS系统中的恒星星族数据提供了一套有价值的经验等时线。我们还比较了我们的新推导的CMD维多利亚等时线已被转换到观察到的平面，使用最近的经验和理论的颜色Teff关系。这些模型能够很好地再现富金属原子团簇的全部CMD，只要假设相同的红化和距离模量能很好地拟合Johnson-Reinins BV（RI）C光度计的等时线。然而，预测的巨型分支系统变得比观察到的RGBs的金属丰度降低。这些差异的可能解释进行了讨论。
英文摘要：
We have obtained broad-band near-infrared photometry for seven Galactic star clusters (M92, M15, M13, M5, NGC1851, M71 and NGC6791) using the WIRCam wide-field imager on the Canada-France-Hawaii Telescope, supplemented by images of NGC1851 taken with HAWK-I on the VLT. In addition, 2MASS observations of the [Fe/H] ~ 0.0 open cluster M67 were added to the cluster database. From the resultant (V-J)-V and (V-Ks)-V colour-magnitude diagrams (CMDs), fiducial sequences spanning the range in metallicity, -2.4 < [Fe/H] < +0.3, have been defined which extend (for most clusters) from the tip of the red-giant branch (RGB) to ~ 2.5 magnitudes below the main-sequence turnoff. These fiducials provide a valuable set of empirical isochrones for the interpretation of stellar population data in the 2MASS system. We also compare our newly derived CMDs to Victoria isochrones that have been transformed to the observed plane using recent empirical and theoretical colour-Teff relations. The models are able to reproduce the entire CMDs of clusters more metal rich than [Fe/H] ~ -1.4 quite well, on the assumption of the same reddenings and distance moduli that yield good fits of the same isochrones to Johnson-Cousins BV(RI)C photometry. However, the predicted giant branches become systematically redder than the observed RGBs as the cluster metallicity decreases. Possible explanations for these discrepancies are discussed.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
