THE IMPACT OF POINT-SOURCE SUBTRACTION RESIDUALS ON 21 cm EPOCH OF REIONIZATION ESTIMATION

By Cathryn M. Trott, Randall B. Wayth, Steven J. Tingay. 2012

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Precise subtraction of foreground sources is crucial for detecting and estimating 21 cm H i signals from the Epoch of Reionization (EoR). We quantify how imperfect point-source subtraction due to limitations of the measurement data set yields structured residual signal in the data set. We use the Cramer–Rao lower bound, as a metric for quantifying the precision with which a parameter may be measured, to estimate the residual signal in a visibility data set due to imperfect point-source subtraction. We then propagate these residuals into two metrics of interest for 21 cm EoR experiments—the angular power spectrum and two-dimensional power spectrum—using a combination of full analytic covariant derivation, analytic variant derivation, and covariant Monte Carlo simulations. This methodology differs from previous work in two ways: (1) it uses information theory to set the point-source position error, rather than assuming a global rms error, and (2) it describes a method for propagating the errors analytically, thereby obtaining the full correlation structure of the power spectra. The methods are applied to two upcoming low-frequency instruments that are proposing to perform statistical EoR experiments: the Murchison Widefield Array and the Precision Array for Probing the Epoch of Reionization. In addition to the actual antenna configurations, we apply the methods to minimally redundant and maximally redundant configurations. We find that for peeling sources above 1 Jy, the amplitude of the residual signal, and its variance, will be smaller than the contribution from thermal noise for the observing parameters proposed for upcoming EoR experiments, and that optimal subtraction of bright point sources will not be a limiting factor for EoR parameter estimation. We then use the formalism to provide an ab initio analytic derivation motivating the “wedge” feature in the two-dimensional power spectrum, complementing previous discussion in the literature.

Subfields: Aerospace Engineering, Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a4bf262b74cf0fb371ad7fec943ff982f9bebf0c

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Citations in the corpus

PAPER-64 CONSTRAINTS ON REIONIZATION: THE 21 cm POWER SPECTRUM AT z = 8.4 (2015, methodology): “Review of OQEs We use the OQE method to estimate our power spectrum as done in Liu & Tegmark (2011), Dillon et al. (2013), Liu et al. (2014a), Liu et al. (2014b), and Trott et al. (2012).”
Calibration requirements for detecting the 21 cm epoch of reionization power spectrum and implications for the SKA (2016, background): “…wedge” due to the mode-mixing of power from small k‖ values into larger k‖ values as demonstrated in Figure 1 (Datta et al. 2010; Morales et al. 2012; Vedantham et al. 2012; Parsons et al. 2012b; Trott et al. 2012; Hazelton et al. 2013; Thyagarajan et al. 2013; Pober et al. 2013; Liu et al. 2014).”
21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, background): “…across all frequencies, but instead localize the majority of the foreground noise into a foreground ‘wedge’ within cylindrical 2D k-space (Datta et al. 2010; Morales et al. 2012; Parsons et al. 2012b; Trott et al. 2012; Vedantham et al. 2012; Thyagarajan et al. 2013; Liu et al. 2014a,b).”
Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “– Subtraction of bright sources (down to the noise level; see e.g. Trott et al. 2012) requires construction of accurate source models.”
FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7 (2016, background): “…the result of instrumental mode mixing, throwing power from spectrally smooth foregrounds to higher Fourier modes (Thyagarajan et al. 2015a,b; Trott et al. 2012; Liu et al. 2014a,b; Hazelton et al. 2013; Pober et al. 2013; Thyagarajan et al. 2013; Vedantham et al. 2012; Morales et al.…”
Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR (2020, methodology): “…instrument (in both the PSF and the primary beam), and chromatic calibration errors create additional ‘modemixing’ foreground contaminants which introduce spectral structure to the otherwise smooth foregrounds (Datta et al. 2010; Morales et al. 2012; Trott et al. 2012; Vedantham et al. 2012).”
WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION (2013, background): “…that has arisen in the last few years, i.e., the division of 2D cylindrical k-space into the foreground-contaminated “wedge” and the relatively clean “EoR window” (Datta et al. 2010; Vedantham et al. 2012; Morales et al. 2012; Parsons et al. 2012b; Trott et al. 2012; Thyagarajan et al. 2013).”
OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER (2013, methodology): “…this resolution is set by the 25 MHz bandwidth used in the analysis.15 The most prominent feature is the “wedge”-like shape of the foreground emissison as predicted in a number of studies, including Datta et al. (2010), Vedantham et al. (2012), Morales et al. (2012), Trott et al. (2012), and P12b.”