RADIATIVE TRANSFER MODEL OF DUST ATTENUATION CURVES IN CLUMPY, GALACTIC ENVIRONMENTS
RADIATIVE TRANSFER MODEL OF DUST ATTENUATION CURVES IN CLUMPY, GALACTIC ENVIRONMENTS
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DOI：
10.3847/1538-4357/833/2/201
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发表时间：
2016-06
期刊：
影响因子：
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通讯作者：
K. Seon;B. Draine
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文献类型：
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作者：
K. Seon;B. Draine
通过球形块状星际介质（ISM）的辐射传输模型，研究了星系环境中尘埃对星光的衰减。我们发现衰减曲线主要由吸收的波长依赖性决定，而不是由底层消光（吸收+散射）曲线决定；除非指定吸收或散射效率，否则观测导出的衰减曲线不能约束唯一的消光曲线。通过假设银河系的硅酸盐-碳质尘埃模型（MW），发现了与“Calzetti曲线”一致的衰减曲线，但2175 Å碰撞被抑制或不存在。我们的结果与先前声称小麦哲伦星云尘埃是Calzetti曲线起源的工作之间的差异归因于采用反照率的差异；我们使用的是理论计算的反照率，而以前的工作采用的是由反射星云观测经验得出的反照率。结果表明，用该模型计算的衰减曲线可以很好地表示为斜率和UV凹凸强度变化的修正Calzetti曲线。当UV碰撞载体的丰度被假设为MW尘埃的30%-40%时，在恒星形成星系中发现的斜率与UV碰撞强度之间的强相关性得到了很好的重现；辐射传输效应导致衰减曲线较浅，紫外线凸起较弱，因为ISM更块状和粉尘较多。我们还认为，一些当地的星暴星系在它们的衰减曲线上有一个紫外线凸起，尽管非常微弱。
The attenuation of starlight by dust in galactic environments is investigated through models of radiative transfer in a spherical, clumpy interstellar medium (ISM). We show that the attenuation curves are primarily determined by the wavelength dependence of absorption rather than by the underlying extinction (absorption+scattering) curve; the observationally derived attenuation curves cannot constrain a unique extinction curve unless the absorption or scattering efficiency is specified. Attenuation curves consistent with the “Calzetti curve” are found by assuming the silicate-carbonaceous dust model for the Milky Way (MW), but with the 2175 Å bump suppressed or absent. The discrepancy between our results and previous work that claimed the Small Magellanic Cloud dust to be the origin of the Calzetti curve is ascribed to the difference in adopted albedos; we use the theoretically calculated albedos, whereas the previous works adopted albedos derived empirically from observations of reflection nebulae. It is found that the attenuation curves calculated with the MW dust model are well represented by a modified Calzetti curve with a varying slope and UV bump strength. The strong correlation between the slope and UV bump strength, as found in star-forming galaxies at , is well reproduced when the abundance of the UV bump carriers is assumed to be 30%–40% of that of the MW dust; radiative transfer effects lead to shallower attenuation curves with weaker UV bumps as the ISM is more clumpy and dustier. We also argue that some local starburst galaxies have a UV bump in their attenuation curves, albeit very weak.