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Title: An Improved Statistical Point-source Foreground Model for the Epoch of Reionization

Abstract

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parametermore » choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.« less

Authors:
; ;  [1]
  1. ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia)
Publication Date:
OSTI Identifier:
22663295
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 845; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; DETECTION; EMISSION; FLUX DENSITY; HYDROGEN; REDUCTION; SPATIAL DISTRIBUTION; SPECTRA; UNIVERSE

Citation Formats

Murray, S. G., Trott, C. M., and Jordan, C. H. An Improved Statistical Point-source Foreground Model for the Epoch of Reionization. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7D0A.
Murray, S. G., Trott, C. M., & Jordan, C. H. An Improved Statistical Point-source Foreground Model for the Epoch of Reionization. United States. doi:10.3847/1538-4357/AA7D0A.
Murray, S. G., Trott, C. M., and Jordan, C. H. Thu . "An Improved Statistical Point-source Foreground Model for the Epoch of Reionization". United States. doi:10.3847/1538-4357/AA7D0A.
@article{osti_22663295,
title = {An Improved Statistical Point-source Foreground Model for the Epoch of Reionization},
author = {Murray, S. G. and Trott, C. M. and Jordan, C. H.},
abstractNote = {We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.},
doi = {10.3847/1538-4357/AA7D0A},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 845,
place = {United States},
year = {2017},
month = {8}
}