A simple model for the absorption of starlight by dust in galaxies
A simple model for the absorption of starlight by dust in galaxies
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DOI：
10.1086/309250
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发表时间：
2000-08-20
影响因子：
4.9
通讯作者：
Fall, SM
中科院分区：
文献类型：
--
作者：
Charlot, S;Fall, SM
我们提出了一个新的模型，用于计算尘埃对星系的综合光谱特性的影响，基于星际介质（ISM）的主要特征的理想化描述。该模型包括电离的H II区域的内部致密的云，其中恒星的形式和影响的有限寿命的这些云的辐射吸收。我们计算的生产的发射线和连续辐射的吸收在H II区域和随后的转移线和连续辐射在周围的H I区域和周围的ISM。这使我们能够同时解释所有的观测结果的紫外线选择的样本附近的星暴星系，包括远红外线的比紫外线光度，H α的比H β光度，H α的等效宽度，和紫外光谱斜率。我们表明，恒星诞生云的有限寿命是解决星暴星系中的线和连续光子的衰减之间的明显差异的关键因素。此外，我们发现，一个有效的吸收曲线成比例的λ（-0.7）再现了观察到的远红外到紫外光的光度比和紫外光谱斜率之间的关系。我们解释这种关系最简单的是作为一个序列中的总尘埃含量的星系。浅波长的有效吸收曲线的依赖性是兼容与已知的消光曲线的陡峭性，如果灰尘有一个斑片状分布。特别是，我们发现，一个随机分布的离散云的光学深度类似于那些在银河系提供了一个一致的解释所有的观测。我们详细分析的一个值得注意的结果是，观测到的星暴星系的平均关系可以通过以下简单的公式近似：使用与λ成比例的有效吸收曲线（-0.7）衰减来自每一代恒星的线辐射和连续辐射，并降低曲线的归一化，通常在10（7）年后降低3倍，来解释出生云的消散这个配方或我们的完整吸收模型可以很容易地纳入任何人口合成模型。
We present a new model for computing the effects of dust on the integrated spectral properties of galaxies, based on an idealized description of the main features of the interstellar medium (ISM). The model includes the ionization of H II regions in the interiors of the dense clouds in which stars form and the influence of the finite lifetime of these clouds on the absorption of radiation. We compute the production of emission lines and the absorption of continuum radiation in the H II regions and the subsequent transfer of line and continuum radiation in the surrounding H I regions and the ambient ISM. This enables us to interpret simultaneously all the observations of an ultraviolet-selected sample of nearby starburst galaxies, including the ratio of far-infrared to ultraviolet luminosities, the ratio of H alpha to H beta luminosities, the H alpha equivalent width, and the ultraviolet spectral slope. We show that the finite lifetime of stellar birth clouds is a key ingredient for resolving an apparent discrepancy between the attenuation of line and continuum photons in starburst galaxies. In addition, we find that an effective absorption curve proportional to lambda(-0.7) reproduces the observed relation between the ratio of far-infrared to ultraviolet luminosities and the ultraviolet spectral slope. We interpret this relation most simply as a sequence in the overall dust content of the galaxies. The shallow wavelength dependence of the effective absorption curve is compatible with the steepness of known extinction curves if the dust has a patchy distribution. In particular, we find that a random distribution of discrete clouds with optical depths similar to those in the Milky Way provides a consistent interpretation of all the observations. A noteworthy outcome of our detailed analysis is that the observed mean relations for starburst galaxies can be closely approximated by the following simple recipe: use an effective absorption curve proportional to lambda(-0.7) to attenuate the line and continuum radiation from each stellar generation, and lower the normalization of the curve, typically by a factor of 3 after 10(7) yr, to account for the dispersal of the birth clouds. This recipe or our full model for absorption can be incorporated easily into any population synthesis model.