约束内部钢筋的形成。NGC 357的光度学、运动学和恒星星族
Constraining the formation of inner bars. Photometry, kinematics and stellar populations in NGC 357
摘要：
双棒星系在本地宇宙中很常见，大约三分之一的棒旋星系拥有一个较小的内部棒。嵌套的棒被认为是一种将气体输送到星系中心区域的机制，触发了恒星的形成，并有助于凸起的增长。为了验证这一观点，我们首次对一个双棒星系NGC 357的光度学、运动学和恒星星族进行了详细的分析。我们发现，这个星系要么是主办一个pseudoclull或经典的鼓与一个内盘。我们比较了（假）隆凸、内坝和外坝的相对平均亮度加权年龄、金属丰度和α增强，发现这三个结构几乎是同时代的和古老的。此外，凸起和内部酒吧呈现相同的金属丰度和过剩，而外部酒吧往往是少金属丰富和更多的α增强。这些结果指出，与气体和恒星形成起主要作用的经典长期情景不同，现有恒星的重新分布正在推动内部结构的形成。
英文摘要：
Double-barred galaxies are common in the local Universe, with approximately one third of barred spirals hosting an smaller, inner bar. Nested bars have been proposed as a mechanism for transporting gas to the very central regions of the galaxy, trigger star formation and contribute to the growth of the bulge. To test this idea, we perform for the first time a detailed analysis of the photometry, kinematics and stellar populations of a double-barred galaxy: NGC 357. We find that this galaxy is either hosting a pseudobulge or a classical bulge together with an inner disc. We compare the relative mean luminosity-weighted age, metallicity and alpha-enhancement between the (pseudo)bulge, inner bar and outer bar, finding that the three structures are nearly coeval and old. Moreover, the bulge and inner bar present the same metallicity and overabundance, whereas the outer bar tends to be less metal-rich and more alpha-enhanced. These results point out that, rather than the classical secular scenario in which gas and star formation play a major role, the redistribution of the existing stars is driving the formation of the inner structures.
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