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arXiv 1401.7669astro-ph.GAastro-ph.CO
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星暴星系M82的全色分析:探测尘埃性质

A panchromatic analysis of starburst galaxy M82: Probing the dust properties

S. Hutton, I. Ferreras, K. Wu, N. P. M. Kuin, A. Breeveld, V. Yershov, M. Cropper, M. J. Page

摘要:

我们结合近距离星暴星系M82的NUV、光学和红外成像,探讨了星系星际介质中尘埃和超风中尘埃的性质。Swift/UVOT的三个NUV滤波器使我们能够详细探测2175 A凸点周围区域的消光曲线特性。NUV的色-色图强烈地排除了卡尔泽蒂型定律,它既可以反映尘埃性质的内在变化,也可以反映恒星形成历史的内在变化,而恒星爆发则可以很好地用这种衰减定律来代表。我们强调,它主要是在NUV区域,一个标准的牛奶路型法律是首选的卡尔泽蒂法律。这些恒星星族的年龄和尘埃分布与最近4亿年来与M81相遇的情况是一致的。在超风区的NUV和光学颜色的径向梯度支持的假设,即在风锥中的排放是由喷出物中夹带的尘埃颗粒的散射驱动。观察到的波长依赖性揭示了一个晶粒尺寸分布$n(a)\propto a^{-2.5}$,其中$a$是晶粒的大小,或一个平坦的分布与最大尺寸截止,这表明只有小晶粒夹带在超新星驱动的风。

英文摘要:

(Abridged) We combine NUV, optical and IR imaging of the nearby starburst galaxy M82 to explore the properties of the dust both in the interstellar medium of the galaxy and the dust entrained in the superwind. The three NUV filters of Swift/UVOT enable us to probe in detail the properties of the extinction curve in the region around the 2175A bump. The NUV colour-colour diagram strongly rules out a Calzetti-type law, which can either reflect intrinsic changes in the dust properties or in the star formation history compared to starbursts well represented by such an attenuation law. We emphasize that it is mainly in the NUV region where a standard Milky-Way-type law is preferred over a Calzetti law. The age and dust distribution of the stellar populations is consistent with the scenario of an encounter with M81 in the recent 400 Myr. The radial gradients of the NUV and optical colours in the superwind region support the hypothesis that the emission in the wind cone is driven by scattering from dust grains entrained in the ejecta. The observed wavelength dependence reveals either a grain size distribution $n(a)\propto a^{-2.5}$, where $a$ is the size of the grain, or a flatter distribution with a maximum size cutoff, suggesting that only small grains are entrained in the supernovae-driven wind.

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