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Title: All-sky interferometry with spherical harmonic transit telescopes

In this paper, we describe the spherical harmonic transit telescope through the use of a novel formalism for the analysis of transit radio telescopes. This all-sky approach bypasses the curved-sky complications of traditional interferometry and so is particularly well-suited to the analysis of wide-field radio interferometers. It enables compact and computationally efficient representations of the data and its statistics, which allow new ways of approaching important problems like map-making and foreground removal. In particular, we show how it enables the use of the Karhunen-Loève transform as a highly effective foreground filter, suppressing realistic foreground residuals for our fiducial example by at least a factor 20 below the 21 cm signal, even in highly contaminated regions of the sky. This is despite the presence of the mode-mixing inherent in real-world instruments with frequency-dependent beams. We show, using Fisher forecasting, that foreground cleaning has little effect on power spectrum constraints compared to hypothetical foreground-free measurements. Beyond providing a natural real-world data analysis framework for 21 cm telescopes now under construction and future experiments, this formalism allows accurate power spectrum forecasts to be made that include the interplay of design constraints and realistic experimental systematics with 21st century 21 cm science.
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
  2. Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
  3. Theoretical Astrophysics Group, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)
Publication Date:
OSTI Identifier:
22348140
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BEAMS; COSMOLOGY; DATA ANALYSIS; EARTH PLANET; FILTERS; FORECASTING; FREQUENCY DEPENDENCE; GLOBAL ASPECTS; INTERFEROMETERS; INTERFEROMETRY; LIMITING VALUES; MIXING; NONLUMINOUS MATTER; RADIO TELESCOPES; SKY; SPECTRA; SPHERICAL CONFIGURATION; UNIVERSE