arXiv 1802.077722018-02-21astro-ph.GA

再电离时期的尘埃星系：模拟

Dusty galaxies in the Epoch of Reionization: simulations

C. Behrens, A. Pallottini, A. Ferrara, S. Gallerani, L. Vallini

备注：: 15 pages, accepted for publication in MNRAS
DOI：: 10.1093/mnras/sty552

摘要：

最近发现的尘埃星系进入了再电离时代（红移$z>6$），这对这些原始系统中星际介质的性质提出了挑战性的问题。通过结合最先进的流体动力学和尘埃辐射传输模拟，我们解决了这些问题，重点关注最近发现的尘埃星系A2744_YD4（$z=8.38$，Laporte et al. 2017}）。我们表明，我们可以只使用与Laporte等人（2017）推断的不同的物理值来重现观测到的光谱能量分布（SED），即恒星形成率为$\mathrm{SFR} = 78\;\rm M_\odot \rm yr^{-1}$，比简单的光谱能量分布拟合推导出的高$\approx 4$。在这种情况下，我们发现：（a）粉尘衰减（对应于$τ_V=1.4$）与银河系消光曲线一致;（b）尘埃-金属比低，$f_\mathrm{d} \sim 0.08$，意味着早期尘埃形成效率相当低;（c）亮度加权尘埃温度高，$T_d=91\pm 23\, \rm K$，这是强烈的（d）由于高$\approx 100\times$，ALMA波段7的探测可以用有限的尘埃质量$M_d=1.6\times 10^6 $ M $_\odot$来解释。最后，高尘埃温度可能解决了最近从IRX- $β$关系推导出的高$z$星系令人困惑的低红外过量。

英文摘要：

The recent discovery of dusty galaxies well into the Epoch of Reionization (redshift $z>6$) poses challenging questions about the properties of the interstellar medium in these pristine systems. By combining state-of-the-art hydrodynamic and dust radiative transfer simulations, we address these questions focusing on the recently discovered dusty galaxy A2744_YD4 ($z=8.38$, Laporte et al. 2017}). We show that we can reproduce the observed spectral energy distribution (SED) only using different physical values with respect to the inferred ones by Laporte et al(2017), i.e. a star formation rate of $\mathrm{SFR} = 78\;\rm M_\odot \rm yr^{-1}$, a factor $\approx 4$ higher than deduced from simple Spectral Energy Distribution fitting. In this case we find: (a) dust attenuation (corresponding to $τ_V=1.4$) is consistent with a Milky Way extinction curve; (b) the dust-to-metal ratio is low, $f_\mathrm{d} \sim 0.08$, implying that early dust formation is rather inefficient; (c) the luminosity-weighted dust temperature is high, $T_d=91\pm 23\, \rm K$, as a result of the intense ($\approx 100\times$ MW) interstellar radiation field; (d) due to the high $T_d$, the ALMA Band 7 detection can be explained by a limited dust mass, $M_d=1.6\times 10^6 $M$_\odot$. Finally, the high dust temperatures might solve the puzzling low infrared excess recently deduced for high-$z$ galaxies from the IRX-$β$ relation.

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