一种利用ENGAWA模拟的银河系晕色散量新模型：低色散量与大各向异性
A New Model for the Milky Way Halo Dispersion Measure with the ENGAWA Simulations: Low DMs and Large Anisotropy
AI总结：
研究利用ENGAWA模拟套件约束银河系晕的色散量贡献，发现其平均晕DM值更低且各向异性更大，通过改变太阳位置估计了DM不确定性，提供相关Python包，为FRB观测解释和宇宙气体分布理解提供关键基线。
AI中文摘要：
快速射电暴（FRB）色散量（DM）是低密度宇宙的有力追踪器，但DM的积分性质使其解释困难。本文分析新的ENGAWA宇宙学放大模拟套件以约束银河系（MW）晕的DM贡献。ENGAWA模拟由四个类似银河系的星系组成，在星系际介质中分辨率增强，是探测气态晕性质的优秀工具。ENGAWA中星系晕的全天空DM中位数在19 - 39 pc cm⁻³之间，即使在固定反馈强度、晕质量和f_CGM时也有变化。这些模拟表明，随着星系际分辨率增强，平均晕DM值总体更低，且全天空各向异性更大，两极处小于10 pc cm⁻³。通过改变模拟星系内太阳位置，得到了因我们在MW中的位置导致的DM不确定性估计。提供了一个Python包，可通过银河经度和纬度的API函数获取模拟中的MW晕DM值。这些基于模拟的新MW晕DM估计将为未来FRB观测解释及我们对宇宙中全球气体分布的理解提供关键基线。
英文摘要：
Fast radio burst (FRB) dispersion measures (DMs) are powerful tracers of the low density universe, but interpretation is made difficult by the integrated nature of DM. In this paper, we analyze the new ENGAWA cosmological zoom-in simulation suite to constrain the DM contribution from the Milky Way (MW) halo. The ENGAWA simulations consist of four Milky Way-like galaxies with enhanced resolution in the circumgalactic medium, making them an excellent tool to probe the properties of the gaseous halo. The median all-sky DM from the galactic halos in ENGAWA span 19-39 pc cm$^{-3}$, varying even at fixed feedback strength, halo mass, and $f_\mathrm{CGM}$. These simulations show that, with enhanced circumgalactic resolution, the mean halo DM values are in general lower with more anisotropy across the sky than previous models, reaching < 10 pc cm$^{-3}$ towards the poles. Furthermore, by varying the solar position within the simulated galaxies, we have obtained an estimate of the uncertainty in DM given our location in the MW. We provide a Python package with MW halo DM values from the simulation accessible via API functions of Galactic longitude and latitude. These new, simulation-based MW halo DM estimates will provide a critical baseline for interpretations of future FRB observations and our understanding of the global gas distribution in the Universe.
