A method for 21 cm power spectrum estimation in the presence of foregrounds

By Adrian Liu, Max Tegmark. Physical Review D, 2011

138 citations recorded by the source corpus.

The technique of 21 cm tomography promises to be a powerful tool for estimating cosmological parameters, constraining the epoch of reionization, and probing the so-called dark ages. However, realizing this promise will require the extraction of a cosmological power spectrum from beneath overwhelmingly large sources of foreground contamination. In this paper, we develop a unified matrix-based framework for foreground subtraction and power spectrum estimation, which allows us to quantify the errors and biases that arise in the power spectrum as a result of foreground subtraction. We find that existing line-of-sight foreground subtraction proposals can lead to substantial mode mixing as well as residual noise and foreground biases, whereas our proposed inverse-variance foreground subtraction eliminates noise and foreground biases, gives smaller error bars, and produces less correlated measurements of the power spectrum. We also numerically confirm the intuitive belief in the literature that 21 cm foreground subtraction is best done using frequency rather than angular information.

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

View Paper: https://www.semanticscholar.org/paper/c8c064295a08d49979c1b3ef21a1904f06963bf3

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Citations in the corpus

INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, background): “In fact, modes on smaller scales will have suppressed power due to aliasing effects, though if correctly handled one can still obtain unbiased estimates of the power spectrum at these scales, albeit with somewhat larger variance (Petrovic & Oh 2011, Liu & Tegmark 2011).”
Hydrogen Epoch of Reionization Array (HERA) (2016, background): “…is to first make an image cube of the sky as a function of angular position and frequency, take the spatial Fourier transform, square and bin the cube, then subtract the dominant foreground power and take the transform to determine the EOR power spectrum (Liu & Tegmark 2011; Dillon et al. 2013).”
Determination of z ∼ 0.8 neutral hydrogen fluctuations using the 21 cm intensity mapping autocorrelation (2013, background): “In the absence of instrumental effects, these degrees of freedom are thought to be separable from the signal (Liu & Tegmark 2011, 2012; Shaw et al. 2013).”
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).”
THE IMPACT OF POINT-SOURCE SUBTRACTION RESIDUALS ON 21 cm EPOCH OF REIONIZATION ESTIMATION (2012, methodology): “…to explore methods for removing unresolved sources and diffuse structure, and the effects of these techniques on the signal, but it is typically assumed that the bright source subtraction has been performed perfectly (Bowman et al. 2009; Liu et al. 2009; Liu & Tegmark 2011, and references therein).”
MEASUREMENT OF 21 cm BRIGHTNESS FLUCTUATIONS AT z ∼ 0.8 IN CROSS-CORRELATION (2012, background): “This is motivated by the eigenvectors of smooth synchrotron foregrounds (Liu and Tegmark 2011, 2012).”
H i intensity mapping: a single dish approach (2012, methodology): “(Liu & Tegmark 2011)) can be employed that will allow a detection of BAO.”
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).”
A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE (2012, methodology): “The technique we have presented bears broad similarities to other approaches described in the literature (Morales & Hewitt 2004; Bowman et al. 2009; Liu & Tegmark 2011) in that it seeks to exploit spectral smoothness in foreground removal, and in that it contends with the inherent frequency…”
FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7 (2016, background): “In principle covariance weighting along the frequency dimension may be able to mitigate this leakage (e.g. Liu & Tegmark 2011), and an εppsilon implementation is under development.”
21 cm cosmology in the 21st century (2011, background): “Studies [146, 176, 177] show that, provided the continuum foreground is spectrally smooth in individual sky pixels, it can be removed leaving very little residuals in the cleaned signal.”