解开朝向FRB 190608的宇宙网
Disentangling the Cosmic Web Towards FRB 190608
摘要：
FRB 190608被ASKAP探测到，并定位于SDSS足迹中位于$z_{host}=0.11778$的螺旋星系。与预期的宇宙平均值相比，该爆发具有很大的色散度量（$DM_{FRB}=339.8$ $pc/cm^3$）。它也有一个大的旋转测量（$RM_{FRB}=353$ $rad/m^2$）和散射时间尺度（$τ=3.3$ $ms$ at $1.28$ $GHz$）。Chittidi等人（2020）对宿主星系的紫外线和光学发射进行了详细分析，并估计宿主DM的贡献为$110\pm 37$ $pc/cm^3$。这项工作补充了他们的工作，并报告了对FRB 190608前景星系光学数据的分析，以探索它们对FRB信号的贡献。这两份手稿一起描绘了一个观测驱动的，沿着FRB视线的物质分布的端到端研究;这是同类研究中的第一个。结合KCWI观测和公开的SDSS数据，我们估计了FRB 190608视线上的预期宇宙色散测量值$DM_{cosmic}$。我们首先估计热电离气体在干预维里化晕（$DM_{halos} \approx 7-28$ $pc/cm^3$）的贡献。然后，使用蒙特卡罗绒泡菌机（MCPM）的方法，我们产生了一个三维地图的电离气体在宇宙网丝和计算DM的贡献外晕（$DM_{IGM} \approx 91-126$ $pc/cm^3$）。这意味着沿着这条视线的电离气体的更大部分存在于维里化晕之外。我们还调查了是否干预晕可以占大FRB旋转措施和脉冲宽度，并得出结论，这是难以置信的。脉冲展宽和大的法拉第旋转都可能来自祖先环境或宿主星系。
英文摘要：
FRB 190608 was detected by ASKAP and localized to a spiral galaxy at $z_{host}=0.11778$ in the SDSS footprint. The burst has a large dispersion measure ($DM_{FRB}=339.8$ $pc/cm^3$) compared to the expected cosmic average at its redshift. It also has a large rotation measure ($RM_{FRB}=353$ $rad/m^2$) and scattering timescale ($τ=3.3$ $ms$ at $1.28$ $GHz$). Chittidi et al (2020) perform a detailed analysis of the ultraviolet and optical emission of the host galaxy and estimate the host DM contribution to be $110\pm 37$ $pc/cm^3$. This work complements theirs and reports the analysis of the optical data of galaxies in the foreground of FRB 190608 to explore their contributions to the FRB signal. Together, the two manuscripts delineate an observationally driven, end-to-end study of matter distribution along an FRB sightline; the first study of its kind. Combining KCWI observations and public SDSS data, we estimate the expected cosmic dispersion measure $DM_{cosmic}$ along the sightline to FRB 190608. We first estimate the contribution of hot, ionized gas in intervening virialized halos ($DM_{halos} \approx 7-28$ $pc/cm^3$). Then, using the Monte Carlo Physarum Machine (MCPM) methodology, we produce a 3D map of ionized gas in cosmic web filaments and compute the DM contribution from matter outside halos ($DM_{IGM} \approx 91-126$ $pc/cm^3$). This implies a greater fraction of ionized gas along this sightline is extant outside virialized halos. We also investigate whether the intervening halos can account for the large FRB rotation measure and pulse width and conclude that it is implausible. Both the pulse broadening and the large Faraday rotation likely arise from the progenitor environment or the host galaxy.
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