论文标题
高红色星系的IRX- $β$关系
The IRX-$β$ relation of high-redshift galaxies
论文作者
论文摘要
红外过量（IRX）和紫外光谱斜率（$β_ {\ rm UV} $）之间的关系是星系灰尘特性的经验探针。然而，这种关系的形状，散射和红移演变尚不清楚，导致在高红移处估计星系的灰尘含量和恒星形成速率（SFR）时不确定性。在这项研究中，我们探讨了IRX- $β_ {\ rm UV} $的关系的性质和特性，其样本为$ z = 2-6 $ galaxies（$ m _*\ of 10^9-10^{12}}} \，m_ \ odot $，从高分辨率的fire（Massive Fire）（Massive Fire）（Massive Fire）（Massive Fire（Massive Fire）（FAIR）（FAIR）（FAIR）（FAIR）（FAIR）（FAIRE）（FAIR）（FAIR）（FARMISE FRIET）（FARE）的环境）我们样本中的星系显示IRX- $β_ {\ rm UV} $关系与附近星系中观察到的关系非常吻合。 IRX紧密耦合到UV光学深度，主要由尘埃形式的几何形状而不是总灰尘质量确定，而$β_ {\ rm UV} $既由恒星属性，UV光学上的凹陷和尘埃灭绝定律设置。总体而言，我们样品的IRX- $β_ {\ rm UV} $的大部分散射被发现是由固有的UV光谱斜率的变化驱动的。我们进一步评估IRX- $β_ {\ rm UV} $关系如何取决于观察方向，尘埃金属比，出生云结构和灰尘灭绝定律，我们提出了一个简单的模型，该模型封装了大多数发现的依赖性。因此，我们认为，$ z> 5 $的红外/亚毫米光对象报告的“赤字”并不一定意味着这些时代的非标准尘埃灭绝法。
The relation between infrared excess (IRX) and UV spectral slope ($β_{\rm UV}$) is an empirical probe of dust properties of galaxies. The shape, scatter, and redshift evolution of this relation are not well understood, however, leading to uncertainties in estimating the dust content and star formation rates (SFRs) of galaxies at high redshift. In this study, we explore the nature and properties of the IRX-$β_{\rm UV}$ relation with a sample of $z=2-6$ galaxies ($M_*\approx 10^9-10^{12}\,M_\odot$) extracted from high-resolution cosmological simulations (MassiveFIRE) of the Feedback in Realistic Environments (FIRE) project. The galaxies in our sample show an IRX-$β_{\rm UV}$ relation that is in good agreement with the observed relation in nearby galaxies. IRX is tightly coupled to the UV optical depth, and is mainly determined by the dust-to-star geometry instead of total dust mass, while $β_{\rm UV}$ is set both by stellar properties, UV optical depth, and the dust extinction law. Overall, much of the scatter in the IRX-$β_{\rm UV}$ relation of our sample is found to be driven by variations of the intrinsic UV spectral slope. We further assess how the IRX-$β_{\rm UV}$ relation depends on viewing direction, dust-to-metal ratio, birth-cloud structures, and the dust extinction law and we present a simple model that encapsulates most of the found dependencies. Consequently, we argue that the reported `deficit' of the infrared/sub-millimetre bright objects at $z>5$ does not necessarily imply a non-standard dust extinction law at those epochs.
