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

By Aaron Parsons, Jonathan C. Pober, J. Aguirre, C. Carilli, Daniel C. Jacobs, David F. Moore. 2012

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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 & 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 mK2 near k ∼ 0.2 h Mpc−1 with 132 dipoles in 7 months of observing.

Subfields: Aerospace Engineering, Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/79b5336e81457659e5178c0210b17f0b19c8580a

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Citations in the corpus

PAPER-64 CONSTRAINTS ON REIONIZATION: THE 21 cm POWER SPECTRUM AT z = 8.4 (2015, background): “This approach focuses on spectral smoothness as the primary discriminant between foreground emission and the 21cm reionization signal and applies an understanding of interferometric responses in the delay domain to identify bounds on instrumental chromaticity (Parsons et al. 2012b, hereafter P12b).”
New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, methodology): “These noise simulations agree with Equation 27 of Parsons et al. (2012a), which is the basis of the dashed cyan curve in Figure 6.”
FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7 (2016, background): “We do this by forming a delay spectrum (Parsons et al. 2012) from the raw, uncalibrated visibilities.”
OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER (2013, methodology): “We 14 Derivations of equation 1 in Morales (2005), McQuinn et al. (2006), and Parsons et al. (2012a), relate ΩB to an effective cosmological volume, using a top-hat primary beam or effective area as a pedagogical tool to simplify the result.”
LATE-TIME COSMOLOGY WITH 21 cm INTENSITY MAPPING EXPERIMENTS (2014, background): “…a level that the cosmological signal can be extracted in an unbiased way (Oh & Mack 2003; Barkana & Loeb 2005; Santos et al. 2005; Morales et al. 2006, 2012; Wang et al. 2006; Gleser et al. 2008; Jelić et al. 2008; Liu et al. 2009, 2014; Liu & Tegmark 2011; Petrovic & Oh 2011; Parsons et al. 2012).”
WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION (2013, methodology): “Although the frequency dependence of the primary beam enters into our sensitivity calculations in several places (including the pixel size in the uv plane), the dominant effect is to change the normalization of the noise level in Equation 1.”
An improved source-subtracted and destriped 408 MHz all-sky map (2014, background): “I M ] 1 7 O redshift from the Epoch of Reionization (Jelić et al. 2008; Parsons et al. 2012; Moore et al. 2013; Shaw et al. 2014).”
A simulation-calibrated limit on the H i power spectrum from the GMRT Epoch of Reionization experiment (2013, background): “These foregrounds are currently one of the largest obstacles to detecting the 21 cm signal and several schemes have been developed to address the problem (e.g. Petrovic & Oh 2011; Liu & Tegmark 2011; Chapman et al. 2012; Parsons et al. 2012b; Dillon, Liu & Tegmark 2013).”
Calibration requirements for detecting the 21 cm epoch of reionization power spectrum and implications for the SKA (2016, background): “While this work focuses on sky-based calibration, redundant calibration techniques explicitly depend on the antenna responses being identical (Wieringa 1992; Liu et al. 2010; Parsons et al. 2012a; Noorishad et al. 2012; Zheng et al. 2014).”
21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, methodology): “In this section, we outline only the specifics and assumptions we make in producing our realistic telescope noise profiles, summarizing the key telescope parameters in Table 1, and defer the reader to the more detailed discussions within Parsons et al. (2012a) and Pober et al. (2013, 2014).”
Hydrogen Epoch of Reionization Array (HERA) (2016, methodology): “…and improved, spanning calibration (e.g., Zheng et al. 2014; Jacobs et al. 2016; Barry et al. 2016), handling foreground contamination (e.g., Moore et al. 2013; Thyagarajan et al. 2015b,a; Pober et al. 2016), and the interferometer design itself (e.g., Parsons et al. 2012a; Dillon & Parsons 2016).”