局域宇宙中非均匀初始质量函数的证据
Evidence for a Non-Uniform Initial Mass Function in the Local Universe
摘要：
现代天体物理学中的许多结果都建立在初始质量函数（IMF）是普适的这一概念上。我们在H-α和远紫外（FUV）光下对HI选定星系的观测挑战了这一概念。这两个恒星形成示踪剂的流量比H-α/FUV显示出与H-α和R波段的表面亮度的强相关性：低表面亮度（LSB）星系与高表面亮度星系相比具有较低的比值，并且与使用普遍青睐的IMF参数的平衡恒星形成模型的预期相比。较弱，但显着的相关性的H-α/FUV与光度，自转速度和动力学质量的发现，以及系统的趋势与形态。因此，H-alpha/FUV与其他全局参数的相关变化是更大的星系标度关系家族的一部分。H-alpha/FUV关联不能归因于尘埃校正误差，而恒星形成历史的系统变化不能解释H-alpha和R表面亮度的趋势。LSB星系不太可能有更高的电离光子逃逸分数，考虑到它们的高气体分数和色星等图。最合理的解释的相关性是系统的变化的上限质量和/或斜率的IMF在上端。我们概述了一个场景的压力驱动的相关性，通过设置的效率形成的密集的星团，最大质量的恒星形成。我们的研究结果意味着在星系中测量的恒星形成率对测量中使用的示踪剂非常敏感。一个非普遍的货币基金组织也提出了质疑的解释金属丰度模式的矮星系和恒星形成的历史，来自颜色星等图。节录。
英文摘要：
Many results in modern astrophysics rest on the notion that the Initial Mass Function (IMF) is universal. Our observations of HI selected galaxies in the light of H-alpha and the far-ultraviolet (FUV) challenge this notion. The flux ratio H-alpha/FUV from these two star formation tracers shows strong correlations with the surface-brightness in H-alpha and the R band: Low Surface Brightness (LSB) galaxies have lower ratios compared to High Surface Brightness galaxies and to expectations from equilibrium star formation models using commonly favored IMF parameters. Weaker but significant correlations of H-alpha/FUV with luminosity, rotational velocity and dynamical mass are found as well as a systematic trend with morphology. The correlated variations of H-alpha/FUV with other global parameters are thus part of the larger family of galaxy scaling relations. The H-alpha/FUV correlations can not be due to dust correction errors, while systematic variations in the star formation history can not explain the trends with both H-alpha and R surface brightness. LSB galaxies are unlikely to have a higher escape fraction of ionizing photons considering their high gas fraction, and color-magnitude diagrams. The most plausible explanation for the correlations are systematic variations of the upper mass limit and/or slope of the IMF at the upper end. We outline a scenario of pressure driving the correlations by setting the efficiency of the formation of the dense star clusters where the highest mass stars form. Our results imply that the star formation rate measured in a galaxy is highly sensitive to the tracer used in the measurement. A non-universal IMF also calls into question the interpretation of metal abundance patterns in dwarf galaxies and star formation histories derived from color magnitude diagrams. Abridged.
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