论文标题
EOR前景模型的蒙特卡洛实施无银河免费排放
A Monte Carlo Implementation of Galactic Free-Free Emission for the EoR Foreground Models
论文作者
论文摘要
在电离时期（EOR）期间，对21 cm信号的检测会导致严重的污染。在各种前景组件中，研究较少的无银河空发射，因此它对EOR观察的影响尚不清楚。为了更好地限制这种排放，我们对H $α$发射的蒙特卡洛模拟进行了模拟，该模拟包括直接和分散的H $α$辐射，来自HII区域和温暖的电离培养基（WIM）。 HII区域的位置和半径是从Wise HII目录中引用的，WIM用轴对称模型描述。散射是通过在HI4PI HI地图和指数磁盘模型上应用指数拟合来实现的灰尘和游离电子。使用模拟的H $α$强度，SIMFAST21软件和最新的SKA1-LOW布局配置，用于模拟银河免费发射和EOR信号的SKA“观察到”图像。通过分析一维功率谱，我们发现，无银河免费排放量可以约为$ 10^{5.4} $ - $ 10^{2.1} $，$ 10^{5.0} $ - $ 10^{1.7} $，$ 10^{4.3} $ 10^{4.3} $ 10^$ 10^$ 10^$ 0. Mpc^{ - 1}} <k <2〜 {\ rm mpc^{ - 1}} $在116-124、146-154和186-194 MHz频带中分别分别。我们进一步计算了EOR窗口内的二维功率谱，并表明由银河泄漏的无免费免费排放的功率仍然很重要，因为功率比率可能达到$ 110 \％$ - $ - $ 8000 \％$，$ 30 \％$ - $ - $ - $ 2400 \％\％\％$，$ 10 \％\％$ -250 \％$ 250 \％$ 0.5〜50.5〜 MPC^{ - 1}} \ Lessim K \ Lessim 1〜 {\ rm Mpc^{ - 1}} $在三个频段中。因此，我们指出，应在将来的EOR检测中仔细处理无银河的自由排放。
The overwhelming foreground causes severe contamination on the detection of 21-cm signal during the Epoch of Reionization (EoR). Among various foreground components, the Galactic free-free emission is less studied, so that its impact on the EoR observation remains unclear. To better constrain this emission, we perform the Monte Carlo simulation of H$α$ emission, which comprises direct and scattered H$α$ radiation from HII regions and warm ionized medium (WIM). The positions and radii of HII regions are quoted from the WISE HII catalog, and the WIM is described by an axisymmetric model. The scattering is off dust and free electrons that are realized by applying an exponential fitting to the HI4PI HI map and an exponential disk model, respectively. The simulated H$α$ intensity, the Simfast21 software, and the latest SKA1-Low layout configuration are employed to simulate the SKA "observed" images of Galactic free-free emission and the EoR signal. By analyzing the one-dimensional power spectra, we find that the Galactic free-free emission can be about $10^{5.4}$-$10^{2.1}$, $10^{5.0}$-$10^{1.7}$, and $10^{4.3}$-$10^{1.1}$ times more luminous than the EoR signal on scales of $0.1~{\rm Mpc^{-1}} < k < 2~{\rm Mpc^{-1}}$ in the 116-124, 146-154, and 186-194 MHz frequency bands, respectively. We further calculate the two-dimensional power spectra inside the EoR window and show that the power leaked by Galactic free-free emission can still be significant, as the power ratios can reach about $110\%$-$8000\%$, $30\%$-$2400\%$, and $10\%$-$250\%$ on scales of $0.5~{\rm Mpc^{-1}} \lesssim k \lesssim 1~{\rm Mpc^{-1}}$ in three frequency bands. Therefore, we indicate that the Galactic free-free emission should be carefully treated in future EoR detections.
