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arXiv 1209.2118astro-ph.COastro-ph.GA
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移动网格宇宙学：中性氢在吸收中的性质

Moving mesh cosmology: properties of neutral hydrogen in absorption

Simeon Bird, Mark Vogelsberger, Debora Sijacki, Matias Zaldarriaga, Volker Springel, Lars Hernquist

备注：
13 pages, 11 figures, minor changes to version accepted by MNRAS. Images can be found at http://www.cfa.harvard.edu/itc/research/movingmeshcosmology
发表信息：
Monthly Notices of the Royal Astronomical Society 2013 429 (4): 3341-3352
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摘要：

我们研究中性氢的分布在宇宙学模拟进行了新的移动网格代码AREPO和比较它与相应的GADGET模拟的基础上平滑粒子流体动力学（SPH）技术。这两个代码使用相同的重力求解器和重子物理实现，但求解欧拉方程的方法非常不同，使我们能够评估与流体求解器相关的数值效应如何影响模拟结果。在这里，我们专注于中性气体的分析，在类星体的吸收线检测。我们发现，高列密度政权探测阻尼莱曼α（DLA）和莱曼极限系统（LLS）的代码之间表现出显着的差异。GADGET以气体团块的形式在大晕中产生虚假的伪影，从而增加了LLS横截面。此外，它形成的晕具有比AREPO更密集的中心重子核，这导致了更大的DLA横截面从较小的晕。因此，AREPO产生了一个显着较低的累积丰度的DLAs，这是有趣的，在更接近的协议与观察。然而，柱密度函数的改变不足以显著减少与观察值的差异。对于莱曼-α森林探测的低柱密度气体，代码仅在百分之几的水平上有所不同，这表明这两种方法都很好地描述了这种状态，这一事实令人放心，迄今为止，许多莱曼-α研究都是用SPH进行的。虽然残差小于当前Lyman-alpha森林数据的误差，但我们注意到，这可能会在未来的精度实验中发生变化。

英文摘要：

We examine the distribution of neutral hydrogen in cosmological simulations carried out with the new moving-mesh code AREPO and compare it with the corresponding GADGET simulations based on the smoothed particle hydrodynamics (SPH) technique. The two codes use identical gravity solvers and baryonic physics implementations, but very different methods for solving the Euler equations, allowing us to assess how numerical effects associated with the hydro-solver impact the results of simulations. Here we focus on an analysis of the neutral gas, as detected in quasar absorption lines. We find that the high column density regime probed by Damped Lyman-alpha (DLA) and Lyman Limit Systems (LLS) exhibits significant differences between the codes. GADGET produces spurious artefacts in large halos in the form of gaseous clumps, boosting the LLS cross-section. Furthermore, it forms halos with denser central baryonic cores than AREPO, which leads to a substantially greater DLA cross-section from smaller halos. AREPO thus produces a significantly lower cumulative abundance of DLAs, which is intriguingly in much closer agreement with observations. The column density function, however, is not altered enough to significantly reduce the discrepancy with the observed value. For the low column density gas probed by the Lyman-alpha forest, the codes differ only at the level of a few percent, suggesting that this regime is quite well described by both methods, a fact that is reassuring for the many Lyman-alpha studies carried out with SPH thus far. While the residual differences are smaller than the errors on current Lyman-alpha forest data, we note that this will likely change for future precision experiments.

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