Understanding the properties and physical mechanisms that shape dust attenuation curves in galaxies is one of the fundamental questions of extragalactic astrophysics, with a great practical significance for deriving the physical properties of galaxies, such as the star formation rate and stellar mass. Attenuation curves result from a combination of dust grain properties, dust content, and the spatial arrangement of dust and different populations of stars. In this review we assess the current state of the field, paying particular attention to the importance of extinction curves as the building blocks of attenuation laws. We introduce a quantitative framework to characterize and compare extinction and attenuation curves, present a theoretical foundation for interpreting empirical results, overview an array of observational methods, and review the observational state of the field at both low and high redshift. Our main conclusions are: Attenuation curves exhibit a large range of slopes, from curves with shallow (Milky Way-like) slopes to those exceeding the slope of the SMC extinction curve. The slopes of the curves correlate strongly with the effective optical opacities, in the sense that galaxies with low dust column density (lower visual attenuation) tend to have steeper slopes, whereas the galaxies with high dust column density have shallower (grey) slopes. Galaxies appear to exhibit a diverse range of 2175A UV bump strengths, but on average have suppressed bumps compared to the average Milky Way extinction curve. Theoretical studies indicate that variations in bump strength may result from similar geometric and radiative transfer effects that drive the correlation between the slope and the dust column.

中文翻译：

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星系中的尘埃衰减定律

了解形成星系尘埃衰减曲线的特性和物理机制是河外天体物理学的基本问题之一，对于推导星系的恒星形成率和恒星质量等物理特性具有重要的现实意义。衰减曲线是由尘埃颗粒特性、尘埃含量以及尘埃和不同恒星群的空间排列组合而成的。在这篇综述中，我们评估了该领域的当前状态，特别关注消光曲线作为衰减定律构建块的重要性。我们引入了一个定量框架来表征和比较消光和衰减曲线，提出解释经验结果的理论基础，概述一系列观察方法，并回顾低红移和高红移时场的观测状态。我们的主要结论是： 衰减曲线表现出很大范围的斜率，从具有浅（类似银河系）斜率的曲线到超过 SMC 消光曲线斜率的曲线。曲线的斜率与有效光学不透明度密切相关，从某种意义上说，尘埃柱密度低（视觉衰减较低）的星系往往具有更陡峭的斜率，而尘埃柱密度高的星系则具有更浅的（灰色）斜率。星系似乎表现出不同范围的 2175A 紫外线撞击强度，但与平均银河系消光曲线相比，平均而言，撞击受到抑制。