Radio Astrophysics from the Moon: Constraining Galactic Foreground Maps with Low-Frequency Spectra; General Methods with EDGES Data as a Case Study
Abstract
Upcoming space missions will place the first radio telescopes and lunar observatories on the Moon in order to conduct precision cosmology and astrophysics experiments in a stable environment free from many of the contaminants and systematics inherent to facilities on Earth. The first of these experiments, called ROLSES, will help to characterize this lunar environment, as well as produce low-frequency maps of the galactic foreground. Such maps will be utterly invaluable for 21-cm cosmology, including constraining the Dark Ages and Cosmic Dawn. Many models of the low-frequency radio sky currently rely upon either extrapolating published temperature maps to lower frequencies or upon using principal component analysis to extract the most relevant modes from several maps. Complementary to these analyses, data from the large beam antennas employed in 21-cm global signal experiments also provide information about the spatial and spectral features of the foreground (modulated by the beam) within their band of interest, and these ought to supplement, or in the least be consistent with, the aforementioned models. Using simulations from the Global Sky Model as our mock data, we present a method for generating eigen-spectra of a particular experiment, given numerical simulations of its beam, observation strategy, and location; the first part of this analysis is linear, and can be used to efficiently generate numerous galactic sky maps with various experimental and sky model parameter changes. With the eigen-spectra as a starting point, we then use nonlinear sampling and models to reconstruct the underlying foreground and compare the accuracy of the reconstruction. We run this analysis for various noise levels, numbers of LST bins, and galactic sky parametrizations to understand the effects upon the foreground parameters. Lastly, we apply this method using low-band EDGES data as the mock to constrain the low-frequency galactic sky.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- January 2023
- Bibcode:
- 2023AAS...24110427H