星系盘弯曲、恒星年龄与光廓线无直接耦合
No direct coupling between bending of galaxy disc stellar age and light profiles
摘要：
我们通过全光谱拟合技术研究了卡拉阿尔托遗产积分场区域巡天中44个正面螺旋星系的恒星性质。我们比较的年龄分布与表面亮度分布，以突出配置文件类型之间的差异（I型，指数配置文件;和II，下弯配置文件）。我们观察到一个上翘（“U形”）的年龄分布，这44个星系中的17个可靠的恒星信息到他们的外部。这种“U形”并不是II型星系的独特特征，但也可以在I型星系中观察到。这些发现表明，形成表面亮度和恒星星族分布的机制不是直接耦合的。这种年龄上的上升只在轻重量的剖面中观察到，而在重重量的剖面中则是明显的。考虑到最近对邻近系统外部的研究结果和本信中提出的结果，对年龄上升的最合理解释之一是整个盘的早期形成（$\sim$ ~10~Gyr前），随后是恒星形成的内向外淬火。
英文摘要：
We study the stellar properties of 44 face-on spiral galaxies from the Calar Alto Legacy Integral Field Area survey via full spectrum fitting techniques. We compare the age profiles with the surface brightness distribution in order to highlight differences between profile types (type I, exponential profile; and II, down-bending profile). We observe an upturn ("U-shape") in the age profiles for 17 out of these 44 galaxies with reliable stellar information up to their outer parts. This "U-shape" is not a unique feature for type II galaxies but can be observed in type I as well. These findings suggest that the mechanisms shaping the surface brightness and stellar population distributions are not directly coupled. This upturn in age is only observable in the light-weighted profiles while it flattens out in the mass-weighted profiles. Given recent results on the outer parts of nearby systems and the results presented in this Letter, one of the most plausible explanations for the age upturn is an early formation of the entire disc ($\sim$~10~Gyr ago) followed by an inside-out quenching of the star formation.
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