skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE

Abstract

A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons and Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this techniquemore » substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK{sup 2} near k {approx} 0.2 h Mpc{sup -1} with 132 dipoles in 7 months of observing.« less

Authors:
;  [1]; ;  [2];  [3];  [4]
  1. Astronomy Department, University of California, Berkeley, CA (United States)
  2. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA (United States)
  3. National Radio Astronomy Observatory, Socorro, NM (United States)
  4. School of Earth and Space Exploration, Arizona State University, Tucson, AZ (United States)
Publication Date:
OSTI Identifier:
22092353
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 756; Journal Issue: 2; 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; ACCURACY; AMPLITUDES; ANTENNAS; ASTRONOMY; ASTROPHYSICS; BRIGHTNESS; CALIBRATION; COSMOLOGY; DIPOLES; EMISSION SPECTRA; ENERGY SPECTRA; FREQUENCY DEPENDENCE; HYDROGEN; IMAGES; SENSITIVITY; TELESCOPES; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Parsons, Aaron R., Pober, Jonathan C., Aguirre, James E., Moore, David F., Carilli, Christopher L., and Jacobs, Daniel C. A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE. United States: N. p., 2012. Web. doi:10.1088/0004-637X/756/2/165.
Parsons, Aaron R., Pober, Jonathan C., Aguirre, James E., Moore, David F., Carilli, Christopher L., & Jacobs, Daniel C. A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE. United States. doi:10.1088/0004-637X/756/2/165.
Parsons, Aaron R., Pober, Jonathan C., Aguirre, James E., Moore, David F., Carilli, Christopher L., and Jacobs, Daniel C. Mon . "A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE". United States. doi:10.1088/0004-637X/756/2/165.
@article{osti_22092353,
title = {A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE},
author = {Parsons, Aaron R. and Pober, Jonathan C. and Aguirre, James E. and Moore, David F. and Carilli, Christopher L. and Jacobs, Daniel C.},
abstractNote = {A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons and Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this technique substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK{sup 2} near k {approx} 0.2 h Mpc{sup -1} with 132 dipoles in 7 months of observing.},
doi = {10.1088/0004-637X/756/2/165},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 756,
place = {United States},
year = {2012},
month = {9}
}