A Theory for the Variation of Dust Attenuation Laws in Galaxies
A Theory for the Variation of Dust Attenuation Laws in Galaxies
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DOI：
10.3847/1538-4357/aaed25
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
D. Narayanan;C. Conroy;R. Davé;Benjamin D. Johnson;G. Popping
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文献类型：
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作者：
D. Narayanan;C. Conroy;R. Davé;Benjamin D. Johnson;G. Popping
在本文中，我们提供了一个物理模型的起源变化的形状和碰撞强度的尘埃衰减规律在星系中结合一个大的宇宙学的“放大”星系形成模拟与3D蒙特卡罗尘埃辐射传输计算。我们的模型星系超过三个数量级的恒星质量，从银河系的系统，以高红移的大规模星系。至关重要的是，对于这些计算，我们采用了一个恒定的基本尘埃消光定律在所有情况下，并研究几何形状和辐射传输效应的作用如何影响所得的衰减曲线。我们的主要结果如下。尽管我们使用了一个恒定的尘埃消光曲线，我们发现在派生的衰减规律的戏剧性的变化。归一化衰减定律的斜率主要取决于恒星到尘埃几何的复杂性。增加未被遮蔽的年轻恒星的比例使归一化曲线变平，而增加未被遮蔽的老恒星的比例使曲线变陡。与我们的模型衰减定律的斜率类似，我们发现2175光年紫外线撞击强度的巨大变化，包括一个几乎没有撞击的曲线子集。在我们的模型中，这些撞击强度主要受未被遮蔽的O星和B星的影响，散射光的影响只有次要的影响。总之，这些结果导致衰减曲线斜率和2175 μ m凸块强度之间的自然关系。最后，我们将这些结果应用于25 Mpc h−1箱宇宙流体动力学模拟，以模拟在z = 0到6的整数红移下衰减律的预期色散。一个显着的色散预计在低红移和减少向z = 6。我们提供了在所有红移的最佳拟合中值衰减曲线的列表结果。
In this paper, we provide a physical model for the origin of variations in the shapes and bump strengths of dust attenuation laws in galaxies by combining a large suite of cosmological “zoom-in” galaxy formation simulations with 3D Monte Carlo dust radiative transfer calculations. We model galaxies over three orders of magnitude in stellar mass, ranging from Milky Way–like systems to massive galaxies at high redshift. Critically, for these calculations, we employ a constant underlying dust extinction law in all cases and examine how the role of geometry and radiative transfer effects impacts the resultant attenuation curves. Our main results follow. Despite our usage of a constant dust extinction curve, we find dramatic variations in the derived attenuation laws. The slopes of normalized attenuation laws depend primarily on the complexities of star-to-dust geometry. Increasing fractions of unobscured young stars flatten normalized curves, while increasing fractions of unobscured old stars steepen curves. Similar to the slopes of our model attenuation laws, we find dramatic variation in the 2175 Å ultraviolet bump strength, including a subset of curves with little to no bump. These bump strengths are primarily influenced by the fraction of unobscured O and B stars in our model, with the impact of scattered light having only a secondary effect. Taken together, these results lead to a natural relationship between the attenuation curve slope and 2175 Å bump strength. Finally, we apply these results to a 25 Mpc h−1 box cosmological hydrodynamic simulation in order to model the expected dispersion in attenuation laws at integer redshifts from z = 0 to 6. A significant dispersion is expected at low redshifts and decreases toward z = 6. We provide tabulated results for the best-fit median attenuation curve at all redshifts.