Direct Optimal Mapping Image Power Spectrum and its Window Functions

Kavli Affiliate: Jacqueline N. Hewitt

| First 5 Authors: Zhilei Xu, Honggeun Kim, Jacqueline N. Hewitt, Kai-Feng Chen, Nicholas S. Kern

| Summary:

The key to detecting neutral hydrogen during the epoch of reionization (EoR)
is to separate the cosmological signal from the dominating foreground
radiation. We developed direct optimal mapping (Xu et al. 2022) to map
interferometric visibilities; it contains only linear operations, with full
knowledge of point spread functions from visibilities to images. Here we
present an FFT-based image power spectrum and its window functions based on
direct optimal mapping. We use noiseless simulation, based on the Hydrogen
Epoch of Reionization Array (HERA) Phase I configuration, to study the image
power spectrum properties. The window functions show $<10^{-11}$ power leakage
from the foreground-dominated region into the EoR window; the 2D and 1D power
spectra also verify the separation between the foregrounds and the EoR.
Furthermore, we simulated visibilities from a $uv$-complete array and
calculated its image power spectrum. The result shows that the foreground–EoR
leakage is further suppressed below $10^{-12}$, dominated by the tapering
function sidelobes; the 2D power spectrum does not show signs of the horizon
wedge. The $uv$-complete result provides a reference case for future 21cm
cosmology array designs.

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