اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدContribution of Galactic free-free emission to the foreground for EoR signal in SKA experiments
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The overwhelming foreground contamination hinders the accurate detection of the 21-cm signal of neutral hydrogen 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 observations remains unclear. In this work, we employ the observed $rm Halpha$ intensity map with the correction of dust absorption and scattering, the Simfast21 software, and the latest SKA1-Low layout configuration to simulate the SKA observed images of Galactic free-free emission and the EoR signal. By calculating the one-dimensional power spectra from the simulated image cubes, we find that the Galactic free-free emission is about $10^{3.5}$-$10^{2.0}$, $10^{3.0}$-$10^{1.3}$, and $10^{2.5}$-$10^{1.0}$ 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 $186$-$194$ ${rm MHz}$ frequency bands. We further analyse the two-dimensional power spectra inside the properly defined EoR window and find that the leaked Galactic free-free emission can still cause non-negligible contamination, as the ratios of its power (amplitude squared) to the EoR signal power can reach about $200%$, $60%$, and $15%$ on scales of $1.2~rm Mpc^{-1}$ in three frequency bands, respectively. Therefore, we conclude that the Galactic free-free emission, as a severe contaminating foreground component, needs to be carefully treated in the forthcoming deep EoR observations.
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