We investigate the attenuation law in z ∼ 6 quasars by combining cosmological zoom-in hydrodynamical simulations of quasar host galaxies, with multifrequency radiative transfer calculations. We consider several dust models differing in terms of grain-size distributions, dust mass, and chemical composition, and compare the resulting synthetic spectral energy distributions with data from bright, early quasars. We show that only dust models with grain-size distributions in which small grains ($a\lesssim 0.1~\mu {\rm m}$, corresponding to $\approx 60{{\ \rm per\ cent}}$ of the total dust mass) are selectively removed from the dusty medium provide a good fit to the data. Removal can occur if small grains are efficiently destroyed in quasar environments and/or early dust production preferentially results in large grains. Attenuation curves for these models are close to flat, and consistent with recent data; they correspond to an effective dust-to-metal ratio fd ≃ 0.38, i.e. close to the Milky Way value.

中文翻译：

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z ∼ 6 类星体的尘埃衰减规律

我们通过将类星体宿主星系的宇宙放大流体动力学模拟与多频辐射传输计算相结合，研究 z ∼ 6 类星体的衰减规律。我们考虑了几个在粒度分布、尘埃质量和化学成分方面不同的尘埃模型，并将由此产生的合成光谱能量分布与来自明亮的早期类星体的数据进行比较。我们展示了只有具有粒度分布的尘埃模型，其中小颗粒（$a\lesssim 0.1~\mu {\rm m}$，对应于 $\approx 60{{\ \rm per\ cent}}$ of the总尘埃质量）有选择地从多尘介质中去除，从而很好地拟合数据。如果小颗粒在类星体环境中被有效破坏和/或早期粉尘产生优先导致大颗粒，则可能会发生去除。这些模型的衰减曲线接近平坦，并且与最近的数据一致；它们对应于有效的尘埃金属比 fd ≃ 0.38，即接近银河系的值。