21 cm Tomography with Foregrounds

By Xiaomin Wang, Max Tegmark, Mário G. Santos, Lloyd Knox. 2005

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Twenty-one centimeter tomography is emerging as a powerful tool to explore the reionization epoch and cosmological parameters, but it will only be as good as our ability to accurately model and remove astrophysical foreground contamination. Previous treatments of this problem have focused on the angular structure of the signal and foregrounds and what can be achieved with limited spectral resolution (channel widths in the 1 MHz range). In this paper we introduce and evaluate a "blind" method to extract the multifrequency 21 cm signal by taking advantage of the smooth frequency structure of the Galactic and extragalactic foregrounds. We find that 21 cm tomography is typically limited by foregrounds on scales of k ≪ 1 h Mpc-1 and is limited by noise on scales of k ≫ 1 h Mpc-1, provided that the experimental channel width can be made substantially smaller than 0.1 MHz. Our results show that this approach is quite promising even for scenarios with rather extreme contamination from point sources and diffuse Galactic emission, which bodes well for upcoming experiments such as LOFAR, MWA, PAST, and SKA.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2a245d59852b37d0d96f4fd38d7fc794de0c9832

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Citations in the corpus

Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, methodology): “…removal (e.g., Di Matteo et al. 2004; Pindor et al. 2011; Bernardi et al. 2011), spectral fitting (e.g., Shaver et al. 1999; Santos et al. 2005; Wang et al. 2006; McQuinn et al. 2006; Bowman et al. 2006; Jelić et al. 2008; Harker et al. 2009a, 2010; Petrovic & Oh 2011; Trott et al. 2012), and…”
21 cm cosmology in the 21st century (2011, background): “Studies [142, 172, 173] 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.”
Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization (2005, methodology): “Such preprocessing is common with CMB data sets, and Wang et al. (2006) showed that this procedure can also be used in handling 21 cm observations.”
Reionization and Cosmology with 21-cm Fluctuations (2009, unknown): “A number of techniques have been developed for fitting out the slowly varying foreground emission along each line of sight, including polynomials (McQuinn et al. 2007, Jelic et al. 2008), double log polynomials (Wang et al. 2006), and non-parametric techniques (Harker et al. 2009).”
LATE-TIME COSMOLOGY WITH 21 cm INTENSITY MAPPING EXPERIMENTS (2014, methodology): “…have been proposed for modeling and subtracting the foregrounds (Oh & Mack 2003; Barkana & Loeb 2005; Santos et al. 2005; Morales et al. 2006; Wang et al. 2006; Gleser et al. 2008; Jelić et al. 2008; Liu et al. 2009; Petrovic & Oh 2011), but in this paper we will simply assume that some sort…”
PAPER-64 CONSTRAINTS ON REIONIZATION: THE 21 cm POWER SPECTRUM AT z = 8.4 (2015, methodology): “Foreground removal techniques discussed in the literature include spectral polynomial fitting (Wang et al. 2006; Bowman et al. 2009a; Liu et al. 2009a), principal component analysis (Paciga et al. 2011; Liu & Tegmark 2011; Paciga et al. 2013; Masui et al. 2013), non-parametric subtractions (Harker…”
FOUR FUNDAMENTAL FOREGROUND POWER SPECTRUM SHAPES FOR 21 cm COSMOLOGY OBSERVATIONS (2012, background): “Conceptually, purely angular modes are dominated by the foregrounds, but the EoR signal can be observed in the line-of-sight (frequency) modes (Zaldarriaga et al. 2004; Morales & Hewitt 2004; Jelić et al. 2008; Wang et al. 2006; Harker et al. 2009).”
Foreground simulations for the LOFAR-epoch of reionization experiment (2008, methodology): “Most of the methods rely on the relative smoothness in the frequency of the foregrounds, with respect to the signal (Shaver et al. 1999; Di Matteo et al. 2002; Zaldarriaga, Furlanetto & Hernquist 2004; Morales, Bowman & Hewitt 2006; Wang et al. 2006; Gleser, Nusser & Benson 2007).”
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6 (2010, background): “Removing the foregrounds adequately is essential for detecting the EoR signal (see, e.g., Wang et al. 2006) and much work has been done on simulating foregrounds (e.g. Bowman et al. 2009; Jelić et al. 2010) and designing removal strategies (Morales et al. 2006; Harker et al. 2009; Liu et al. 2009,…”
A model of diffuse Galactic radio emission from 10 MHz to 100 GHz (2008, background): “…is only one to two orders of magnitude worse, the cosmological neutral hydrogen signal is perhaps four orders of magnitudes smaller than the relevant foregrounds (Morales & Hewitt 2004; Bowman, Morales & Hewitt 2006; Furlanetto, Oh & Briggs 2006; Morales, Bowman & Hewitt 2006; Wang et al. 2006).”
FOREGROUND CONTAMINATION IN INTERFEROMETRIC MEASUREMENTS OF THE REDSHIFTED 21 cm POWER SPECTRUM (2008, methodology): “Relating these expressions to the polynomial-based foreground subtraction investigations of Furlanetto & Briggs (2004), Wang et al. (2006), and Gleser et al. (2008), we find that these works treated simplified cases of this general approach by assuming complete coverage of the visibility…”