尘埃宇宙的起源：模拟亚毫米源计数
Genesis of the dusty Universe: modeling submillimetre source counts
摘要：
我们使用唯象方法模拟红外星系的演化，以匹配在不同的红外波长观测到的源计数。我们介绍了一种新的算法，再现源计数的基础上直接集成的概率分布，而不是蒙特卡洛采样。我们构造了一个简单的模型，利用最少的自由参数的光度函数和红外星系的颜色分布的演变。此外，我们还分析了这些参数是如何受到观测数据的约束。该模型基于纯光度演化，采用Dale & Helou SED模板。我们发现，850 μ m源计数和它们的红移分布强烈地依赖于光度演化函数的形状，但对SED的细节只有微弱的依赖。我们推导出最适合的演化模型使用850微米计数和红移分布作为约束条件。此外，我们的最佳拟合显示了一个平坦的亮度函数的暗端向高红移，并需要一个颜色的演变，这意味着具有相同的亮度，以减少红移的对象的典型的尘埃温度。我们比较了我们的最佳拟合模型在较短和较长波长下观察到的源计数，这表明我们的模型非常好地再现了70 um和1100 um源计数，但在中间波长下产生的计数不足。分析表明，出现的差异在低红移，表明修订所采用的SED库对较低的尘埃温度（在一个固定的红外光度）是必要的。这种修改相当于存在于低红移的冷星系群，最近的赫歇尔结果也表明了这一点，这在IRAS样本中表现不足。我们表明，修改后的模型成功地再现了源计数在很宽的范围内的IR和submm波长。
英文摘要：
We model the evolution of IR galaxies using a phenomenological approach to match the observed source counts at different IR wavelengths. We introduce a new algorithm for reproducing source counts based on direct integration of probability distributions rather than Monte-Carlo sampling. We construct a simple model for the evolution of the luminosity function and the colour distribution of IR galaxies which utilizes a minimum number of free parameters. Moreover we analyze how each of these parameters is constrained by observational data. The model is based on pure luminosity evolution and adopts the Dale & Helou SED templates. We find that the 850um source counts and their redshift distribution depend strongly on the shape of the luminosity evolution function, but only weakly on the details of the SEDs. We derive the best-fit evolutionary model using the 850um counts and redshift distribution as constraints. Moreover our best-fit shows a flattening of the faint end of the luminosity function towards high redshifts and requires a colour evolution which implies the typical dust temperatures of objects with the same luminosities to decrease with redshift. We compare our best-fit model to observed source counts at shorter and longer wavelengths which indicates our model reproduces the 70um and 1100um source counts remarkably well, but under-produces the counts at intermediate wavelengths. Analysis reveals that the discrepancy arises at low redshifts, indicating that revision of the adopted SED library towards lower dust temperatures (at a fixed infrared luminosity) is required. This modification is equivalent to a population of cold galaxies existing at low redshifts, as also indicated by recent Herschel results, which are underrepresented in IRAS sample. We show that the modified model successfully reproduces the source counts in a wide range of IR and submm wavelengths.
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