Abstract
Abstract
The absorption feature in the global spectrum is likely the first 21 cm observable from the cosmic dawn, which provides valuable insights into the earliest history of structure formation. We run a set of high-resolution hydrodynamic simulations of early structure formation to assess the effect of nonlinear structure formation on the maximum absorption level (i.e., assuming the spin temperature coupling is saturated) of the global 21 cm spectrum in the standard cosmological framework. We ignore the star formation and feedbacks, which also tend to reduce the absorption signal, but take into account the inevitable nonlinear density fluctuations in the intergalactic medium (IGM), shock-heating, and Compton-heating, which can reduce the absorption level. We found that the combination of these reduced the maximum absorption signal by ∼15% at redshift 17, as compared with the homogeneous or linearly-fluctuating IGM. These effects have to be carefully accounted for when interpreting the observational results, especially when considering the necessity of introducing new physics.
Funder
Ministry of Science and Technology of the People’s Republic of China
National Natural Science Foundation of China
Chinese Academy of Sciences
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
10 articles.
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