Subtracting Foregrounds from Interferometric Measurements of the Redshifted 21 cm Emission
arXiv:1109.5317 · doi:10.1088/0004-637X/744/1/29
Abstract
The ability to subtract foreground contamination from low-frequency observations is crucial to reveal the underlying 21 cm signal. The traditional line-of-sight methods can deal with the removal of diffuse emission and unresolved point sources, but not bright point sources. In this paper, we introduce a foreground cleaning technique in Fourier space, which allows us to handle all such foregrounds simultaneously and thus sidestep any special treatments to bright point sources. Its feasibility is tested with a simulated data cube for the 21 CentiMeter Array experiment. This data cube includes more realistic models for the 21 cm signal, continuum foregrounds, detector noise and frequency-dependent instrumental response. We find that a combination of two weighting schemes can be used to protect the frequency coherence of foregrounds: the uniform weighting in the uv plane and the inverse-variance weighting in the spectral fitting. The visibility spectrum is therefore well approximated by a quartic polynomial along the line of sight. With this method, we demonstrate that the huge foreground contamination can be cleaned out effectively with residuals on the order of \sim10 mK, while the spectrally smooth component of the cosmological signal is also removed, bringing about systematic underestimate in the extracted power spectrum primarily on large scales.
9 pages, 9 figures. Final published version
References in corpus (10)
- Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
- Efficient Simulations of Early Structure Formation and Reionization
- Foreground simulations for the LOFAR - Epoch of Reionization Experiment
- A Method for 21cm Power Spectrum Estimation in the Presence of Foregrounds
- On using visibility correlations to probe the HI distribution from the dark ages to the present epoch I: Formalism and the expected signal
- An Improved Method for 21cm Foreground Removal
- Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations
- Power spectrum extraction for redshifted 21-cm epoch of reionization experiments: the LOFAR case
- Will point sources spoil 21 cm tomography?
- De-contamination of cosmological 21-cm maps
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- Prospects of observing a quasar HII region during the Epoch of Reionization with redshifted 21cm
- Tapering the sky response for angular power spectrum estimation from low-frequency radio-interferometric data
- Contamination of the Epoch of Reionization power spectrum in the presence of foregrounds
- Prospects for detecting the 326.5 MHz redshifted 21 cm HI signal with the Ooty Radio Telescope (ORT)
- Probing reionization with the cross power spectrum of 21 cm and near-infrared radiation backgrounds
- Fisher matrix predictions for detecting the cosmological 21 cm signal with the Ooty Wide Field Array (OWFA)
- Fisher Matrix Based Predictions for Measuring the z = 3.35 Binned 21-cm Power Spectrum using the Ooty Wide Field Array (OWFA)
- Validating a novel angular power spectrum estimator using simulated low frequency radio-interferometric data