The Galactic Halo Contribution to the Dispersion Measure of Extragalactic Fast Radio Bursts
The Galactic Halo Contribution to the Dispersion Measure of Extragalactic Fast Radio Bursts
复制标题
DOI：
10.3847/1538-4357/ab58c4
复制
发表时间：
2019-09
期刊：
影响因子：
--
通讯作者：
S. Yamasaki;T. Totani
中科院分区：
文献类型：
--
作者：
S. Yamasaki;T. Totani
根据最近的漫射X射线观测结果，提出了一个新的银河系晕模型，该模型是对河外源（如快速射电爆发）的色散测度（DM）的一个新的模型。除了与银河系引力势流体静力平衡的等温气体（kT <$0.3 keV）的球形分量外，我们的模型还包括一个盘状非球形热气体分量，以再现所观察到的X射线发射测量（EM）的方向依赖性。总气体质量（1.2 × 1011 M）主要是由球状分量所决定，并且与根据暗物质质量和宇宙重子与暗物质比率所预期的MW的总重子质量一致。我们的模型预测的平均晕DM，与一个完整的范围为30-在整个天空。在X射线EM数据中看到的大散射意味着MW晕DM的dex（rms）波动为1.02。我们提供了一个解析公式来估计MW晕DM我们的模型沿着任何视线，它可以很容易地用来计算总MW组件DM对河外源，结合现有的DM模型的温暖电离介质与银河系盘。
A new model of the Milky Way (MW) halo component of the dispersion measure (DM) for extragalactic sources, such as fast radio bursts, is presented in light of recent diffuse X-ray observations. In addition to the spherical component of isothermal gas (kT ∼ 0.3 keV) in hydrostatic equilibrium with the Galactic gravitational potential, our model includes a disk-like nonspherical hot gas component to reproduce the directional dependence of the observed X-ray emission measure (EM). The total gas mass (1.2 × 1011 M⊙) is dominated by the spherical component, and is consistent with the total baryon mass of the MW expected from the dark matter mass and the cosmic baryon-to-dark-matter ratio. Our model predicts a mean halo DM of , with a full range of 30– over the whole sky. The large scatter seen in the X-ray EM data implies a ∼0.2 dex (rms) fluctuation of the MW halo DM. We provide an analytic formula to estimate the MW halo DM of our model along any line of sight, which can be easily used to compute the total MW component of DM toward extragalactic sources, in combination with existing DM models of the warm ionized medium associated with the Galactic disk.