arXiv 2208.045462022-08-09astro-ph.GA

高红移星系尘埃温度的解析模型

Analytic models of dust temperature in high-redshift galaxies

Hiroyuki Hirashita, I-Da Chiang

备注：: 12 pages, 5 figures, Accepted for publication in MNRAS
DOI：: 10.1093/mnras/stac2242

摘要：

利用解析模型研究了在某些高红移星系（$z>5$）中观测到的高尘埃温度（$T_\mathrm{dust}\gtrsim 40$ K）的物理原因。我们考虑两个模型，可以处理分析：辐射转移（RT）模型，{其中广泛分布的值为$T_\mathrm{dust}$被认为是}，和一个temperature（一个$T$）模型，它假设{均匀$T_\mathrm{dust}$ }。这两个极端{用来概括最现实的情况}。我们采用Kennicutt-Schmidt（KS）定律将恒星辐射场与气体表面密度联系起来，并改变尘气比。因此，我们的模型能够预测恒星形成率的表面密度（$Σ_\mathrm{SFR}$）或尘埃质量（$Σ_\mathrm{dust}$）和$T_\mathrm{dust}$之间的关系。我们发现，在$z\gtrsim 5$观察到的高$T_\mathrm{dust}$有利于低尘气比（$\lesssim 10^{-3}$）。与KS定律相比，增强的恒星形成给出了高$T_\mathrm{dust}$的另一种解释。只要我们使用ALMA波段6- 8，两个模型（RT和一个- $T$）之间的尘埃温度是相似的。在不假设KS定律的情况下，我们还检验了$Σ_\mathrm{SFR}$、$Σ_\mathrm{dust}$和$T_\mathrm{dust}$之间的关系，并证实了与$z>5$实际观测数据的一致性。在一个$T$模型中，我们还研究了一个星团尘埃分布，它预测了较低的$T_\mathrm{dust}$，因为恒星辐射泄漏。这增强了低尘埃丰度或高恒星形成效率的要求，以解释观察到的高$T_\mathrm{dust}$。

英文摘要：

We investigate physical reasons for high dust temperatures ($T_\mathrm{dust}\gtrsim 40$ K) observed in some high-redshift ($z>5$) galaxies using analytic models. We consider two models that can be treated analytically: the radiative transfer (RT) model, {where a broad distribution of values for $T_\mathrm{dust}$ is considered}, and the one-tempearture (one-$T$) model, which assumes {uniform $T_\mathrm{dust}$}. These two extremes {serve to bracket the most realistic scenario}. We adopt the Kennicutt--Schmidt (KS) law to relate stellar radiation field to gas surface density, and vary the dust-to-gas ratio. As a consequence, our model is capable of predicting the relation between the surface density of star formation rate ($Σ_\mathrm{SFR}$) or dust mass ($Σ_\mathrm{dust}$) and $T_\mathrm{dust}$. We show that the high $T_\mathrm{dust}$ observed at $z\gtrsim 5$ favour low dust-to-gas ratios ($\lesssim 10^{-3}$). An enhanced star formation compared with the KS law gives an alternative explanation for the high $T_\mathrm{dust}$. The dust temperatures are similar between the two (RT and one-$T$) models as long as we use ALMA Bands 6--8. We also examine the relation among $Σ_\mathrm{SFR}$, $Σ_\mathrm{dust}$ and $T_\mathrm{dust}$ without assuming the KS law, and confirm the consistency with the actual observational data at $z>5$. In the one-$T$ model, we also examine a clumpy dust distribution, which predicts lower $T_\mathrm{dust}$ because of the leakage of stellar radiation. This enhances the requirement of low dust abundance or high star formation efficiency to explain the observed high $T_\mathrm{dust}$.

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英文摘要：

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