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arXiv 0906.3522astro-ph.CO
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模拟尘埃宇宙I:介绍人工神经网络和首次应用于光度和颜色分布

Modelling the dusty universe I: Introducing the artificial neural network and first applications to luminosity and colour distributions

C. Almeida, C. M. Baugh, C. G. Lacey, C. S. Frenk, G. L. Granato, L. Silva, A. Bressan

摘要:

我们介绍了一种基于人工神经网络的新技术,它使我们能够准确预测大样本星系的光谱能量分布(SED),波长范围从远紫外到亚毫米和无线电。神经网络的训练,以重现SED预测的混合代码组成的GALFORM半分析模型的星系形成,预测完整的恒星形成和星系合并的历史,和GRASIL分光光度代码,进行自洽计算的SED,包括吸收和辐射的尘埃。使用少量的星系性质预测的GALFORM,该方法再现的星系的光度在大多数情况下,直接使用GRASIL计算的10%以内。该方法在亚毫米波段表现最好,在中红外和远紫外波段表现相当好。该方法引入的光度误差对预测的统计分布,如星系的光度函数或颜色分布的影响可以忽略不计。我们使用神经网络来预测星系之间的重叠选择在休息帧UV和在Z=2的双帧子毫米。我们发现,在850 μ m通量大于5 mJy的星系中,约有一半的星系的光学星等应大于R_AB < 25 mag,而在R_AB < 25 mag的静止坐标系中,只有1%的星系的850 μ m通量应大于5 mJy。我们的技术将允许产生广角模拟目录的星系选择在静止帧紫外线或中红外和远红外波长。

英文摘要:

We introduce a new technique based on artificial neural networks which allows us to make accurate predictions for the spectral energy distributions (SEDs) of large samples of galaxies, at wavelengths ranging from the far-ultra-violet to the sub-millimetre and radio. The neural net is trained to reproduce the SEDs predicted by a hybrid code comprised of the GALFORM semi-analytical model of galaxy formation, which predicts the full star formation and galaxy merger histories, and the GRASIL spectro-photometric code, which carries out a self-consistent calculation of the SED, including absorption and emission of radiation by dust. Using a small number of galaxy properties predicted by GALFORM, the method reproduces the luminosities of galaxies in the majority of cases to within 10% of those computed directly using GRASIL. The method performs best in the sub-mm and reasonably well in the mid-infrared and the far-ultra-violet. The luminosity error introduced by the method has negligible impact on predicted statistical distributions, such as luminosity functions or colour distributions of galaxies. We use the neural net to predict the overlap between galaxies selected in the rest-frame UV and in the observer-frame sub-mm at z=2. We find that around half of the galaxies with a 850um flux above 5 mJy should have optical magnitudes brighter than R_AB < 25 mag. However, only 1% of the galaxies selected in the rest-frame UV down to R_AB < 25 mag should have 850um fluxes brighter than 5 mJy. Our technique will allow the generation of wide-angle mock catalogues of galaxies selected at rest-frame UV or mid- and far-infrared wavelengths.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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