Effects of the Surrounding Mountains on the Extraction of Signals from the Global 21 cm Signal Experiment postprint

Abstract: In this paper, we examine the influence of the surrounding mountains around the experimental antenna on the extraction of signals in the global 21 cm experiment. The change in antenna gains introduced by varying the height of the mountain, the angle of slope, the composition of the mountain, the consistency of the composition of the mountain, the distance from the mountain to the antenna, and other factors of the model is simulated using the moment hybrid numerical algorithm. We further analyze the impact of these factors on the antenna in obtaining neutral hydrogen signals. The results show that the characteristics of the mountain, including its height, distance from the observation point, inclination angle, composition material, and surface composition consistency, not only affect the antenna gain, but also further affect the polynomial fitting subtraction of the foreground in the experiment. Specifically, for antenna gain, when the mountain height remains unchanged, the farther the mountain is from the antenna, the smaller the effect on antenna gain.