arXiv 1711.024812017-11-07astro-ph.GAastro-ph.CO

宇宙恒星形成率与本地恒星形成的联系

Connecting the Cosmic Star Formation Rate with the Local Star Formation

Carolina Gribel, Oswaldo D. Miranda, Jose Williams Vilas-Boas

备注：: ApJ accepted
DOI：: 10.3847/1538-4357/aa921a

摘要：

我们提出了一个模型，统一的宇宙恒星形成率（CSFR），通过层次结构形成的情况下，与（银河系）本地恒星形成率（SFR）。通过密度概率分布函数（PDF），可以使用SFR来生成CSFR映射，这些密度概率分布函数通常用于研究银河系恒星形成区域中湍流的作用。我们得到了从红移$z\sim 20$到现在的一致映射（$z = 0$）。我们的研究结果表明，湍流呈现出双重特征，在红移间隔$z\sim 3.5-20$中提供高的恒星形成效率（$\langle\varepsilon\rangle \sim 0.32$）值，并在$z = 0$中将其值降低到$\langle\varepsilon\rangle = 0.021$。$\langle\varepsilon\rangle$从其迅速减小的马赫数（$\mathcal{M}_{\rm crit}$）的值取决于多变指数（$Γ$）和气体的最小密度对比度。我们还推导了与速度色散（$\langle V_{\rm rms}\rangle$）在本地恒星形成区的拉森第一定律。我们的模型在$\sim 10-50\,{\rm pc}$范围内与Larson定律吻合得很好，为与恒星形成相关的气体提供了典型的温度$T_{0} \sim 10-80\,{\rm K}$。因此，大质量的暗物质晕可以包含许多质量小得多的晕，并且能够形成类似于球状星团的结构。因此，拉尔森定律的出现是大尺度结构形成的结果，而大尺度结构反过来又允许银河系的形成，包括我们的银河系。

英文摘要：

We present a model that unifies the cosmic star formation rate (CSFR), obtained through the hierarchical structure formation scenario, with the (Galactic) local star formation rate (SFR). It is possible to use the SFR to generate a CSFR mapping through the density probability distribution functions (PDFs) commonly used to study the role of turbulence in the star-forming regions of the Galaxy. We obtain a consistent mapping from redshift $z\sim 20$ up to the present ($z = 0$). Our results show that the turbulence exhibits a dual character, providing high values for the star formation efficiency ($\langle\varepsilon\rangle \sim 0.32$) in the redshift interval $z\sim 3.5-20$ and reducing its value to $\langle\varepsilon\rangle = 0.021$ at $z = 0$. The value of the Mach number ($\mathcal{M}_{\rm crit}$), from which $\langle\varepsilon\rangle$ rapidly decreases, is dependent on both the polytropic index ($Γ$) and the minimum density contrast of the gas. We also derive Larson's first law associated with the velocity dispersion ($\langle V_{\rm rms}\rangle$) in the local star formation regions. Our model shows good agreement with Larson's law in the $\sim 10-50\,{\rm pc}$ range, providing typical temperatures $T_{0} \sim 10-80\,{\rm K}$ for the gas associated with star formation. As a consequence, dark matter halos of great mass could contain a number of halos of much smaller mass, and be able to form structures similar to globular clusters. Thus, Larson's law emerges as a result of the very formation of large-scale structures, which in turn would allow the formation of galactic systems, including our Galaxy.

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