The Dust Attenuation Law in Galaxies
The Dust Attenuation Law in Galaxies
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DOI：
10.1146/annurev-astro-032620-021933
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发表时间：
2020-01
影响因子：
33.3
通讯作者：
S. Salim;D. Narayanan
中科院分区：
文献类型：
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作者：
S. Salim;D. Narayanan
了解星系中尘埃衰减曲线的性质及其形成的物理机制是河外天体物理学的基本问题之一，对推导星系的物理性质具有重要的现实意义。衰减曲线是由尘埃颗粒的性质、尘埃含量、尘埃的空间排列和不同的恒星群体共同作用的结果。在这篇评论中，我们评估了该领域的状态，特别注意消光曲线作为衰减规律的基石。我们引入了一个定量的框架来描述消光和衰减曲线，提出了解释经验结果的理论基础，概述了一系列的观测方法，并回顾了在低和高红移的观测结果。我们的主要结论包括以下内容：▪衰减曲线表现出广泛的紫外透过光学斜率，从浅（银河系般）斜率的曲线到超过小麦哲伦云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，在这个意义上，具有较低尘柱密度（较低的视觉衰减）的星系往往具有较陡的斜率，而具有较高尘柱密度的星系具有较浅（灰色）的斜率。银河系中的星系呈现出一系列2175- 1000的紫外线强度，包括没有碰撞，但平均而言，与银河系的平均消光曲线相比，受到抑制。▪理论研究表明，坡度与尘柱之间的相关性以及撞击强度的变化都可能是几何和辐射传输效应造成的。
Understanding the properties of dust attenuation curves in galaxies and the physical mechanisms that shape them are among the fundamental questions of extragalactic astrophysics, with great practical significance for deriving the physical properties of galaxies. 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 state of the field, paying particular attention to extinction curves as the building blocks of attenuation laws. We introduce a quantitative framework to characterize extinction and attenuation curves, present a theoretical foundation for interpreting empirical results, overview an array of observational methods, and review observational results at low and high redshifts. Our main conclusions include the following: ▪ Attenuation curves exhibit a wide range of UV-through-optical slopes, from curves with shallow (Milky Way–like) slopes to those exceeding the slope of the Small Magellanic Cloud extinction curve. ▪ The slopes of the curves correlate strongly with the effective optical opacities, in the sense that galaxies with lower dust column density (lower visual attenuation) tend to have steeper slopes, whereas the galaxies with higher dust column density have shallower (grayer) slopes. ▪ Galaxies exhibit a range of 2175-Å UV bump strengths, including no bump, but, on average, are suppressed compared with the average Milky Way extinction curve. ▪ Theoretical studies indicate that both the correlation between the slope and the dust column as well as variations in bump strength may result from geometric and radiative transfer effects.