天炉座3D计划：评估天炉座星团内IMF和恒星星族图的多样性
Fornax 3D project: assessing the diversity of IMF and stellar population maps within the Fornax Cluster
摘要：
恒星初始质量函数（IMF）是我们解释天文观测和理解星系内大多数重子过程的核心。IMF的普遍性，在我们自己的银河系的观测建议，已经彻底重新审视，由于在大质量静止星系的中心区域明显过剩的低质量恒星。作为天炉座3D项目的一部分，我们的目标是表征天炉座星系团内23个静止星系样本的二维IMF变化。对于样本中的每个星系，我们测量了平均年龄，金属丰度，[Mg/Fe]，和IMF斜率图从空间分辨的综合光谱。IMF图显示了各种行为和内部子结构，大致遵循金属丰度的变化。然而，金属丰度本身并不能完全解释IMF地图所表现出的复杂性。特别是，对于相对贫金属的恒星星族，IMF的斜率似乎取决于恒星形成的（特定）恒星形成率。此外，金属丰度图有系统地比IMF斜率更高的椭圆度。与此同时，金属丰度和IMF斜率图同时具有比我们样本星系中恒星光分布更高的椭圆率。此外，我们发现，无论恒星的质量，在我们的样本中的每个星系显示出一个积极的径向[Mg/Fe]梯度。这导致了一个强的[Fe/H]-[Mg/Fe]关系，类似于在附近观察到的，解决星系。由于星系的形成历史和化学富集是因果驱动的IMF的变化，我们的研究结果要求一个物理动机的解释恒星星族测量的基础上，考虑到任何可能的时间演化的恒星星族的综合光谱。
英文摘要：
The stellar initial mass function (IMF) is central to our interpretation of astronomical observables and to our understanding of most baryonic processes within galaxies. The universality of the IMF, suggested by observations in our own Milky Way, has been thoroughly revisited due to the apparent excess of low-mass stars in the central regions of massive quiescent galaxies. As part of the efforts within the Fornax 3D project, we aim to characterize the two-dimensional IMF variations in a sample of 23 quiescent galaxies within the Fornax cluster. For each galaxy in the sample, we measured the mean age, metallicity, [Mg/Fe], and IMF slope maps from spatially resolved integrated spectra. The IMF maps show a variety of behaviors and internal substructures, roughly following metallicity variations. However, metallicity alone is not able to fully explain the complexity exhibited by the IMF maps. In particular, for relatively metal-poor stellar populations, the slope of the IMF seems to depend on the (specific) star formation rate at which stars were formed. Moreover, metallicity maps have systematically higher ellipticities than IMF slope ones. At the same time, both metallicity and IMF slope maps have at the same time higher ellipticities than the stellar light distribution in our sample of galaxies. In addition we find that, regardless of the stellar mass, every galaxy in our sample shows a positive radial [Mg/Fe] gradient. This results in a strong [Fe/H]-[Mg/Fe] relation, similar to what is observed in nearby, resolved galaxies. Since the formation history and chemical enrichment of galaxies are causally driven by changes in the IMF, our findings call for a physically motivated interpretation of stellar population measurements based on integrated spectra that take into account any possible time evolution of the stellar populations.
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