Publication

Non-parametric foreground subtraction for 21-cm epoch of reionization experiments

Harker, G., Zaroubi, S., Bernardi, G., Brentjens, M. A., de Bruyn, A. G., Ciardi, B., Jelic, V., Koopmans, L. V. E., Labropoulos, P., Offringa, A., Pandey, V. N., Schaye, J., Thomas, R. M., Yatawatta, S. & Mellema, G., 1-Aug-2009, In : Monthly Notices of the Royal Astronomical Society. 397, 2, p. 1138-1152 15 p.

Research output: Contribution to journalArticleAcademicpeer-review

APA

Harker, G., Zaroubi, S., Bernardi, G., Brentjens, M. A., de Bruyn, A. G., Ciardi, B., Jelic, V., Koopmans, L. V. E., Labropoulos, P., Offringa, A., Pandey, V. N., Schaye, J., Thomas, R. M., Yatawatta, S., & Mellema, G. (2009). Non-parametric foreground subtraction for 21-cm epoch of reionization experiments. Monthly Notices of the Royal Astronomical Society, 397(2), 1138-1152. https://doi.org/10.1111/j.1365-2966.2009.15081.x

Author

Harker, Geraint ; Zaroubi, Saleem ; Bernardi, Gianni ; Brentjens, Michiel A. ; de Bruyn, A. G. ; Ciardi, Benedetta ; Jelic, Vibor ; Koopmans, Leon V. E. ; Labropoulos, Panagiotis ; Offringa, Andre ; Pandey, V. N. ; Schaye, Joop ; Thomas, Rajat M. ; Yatawatta, Sarod ; Mellema, G. / Non-parametric foreground subtraction for 21-cm epoch of reionization experiments. In: Monthly Notices of the Royal Astronomical Society. 2009 ; Vol. 397, No. 2. pp. 1138-1152.

Harvard

Harker, G, Zaroubi, S, Bernardi, G, Brentjens, MA, de Bruyn, AG, Ciardi, B, Jelic, V, Koopmans, LVE, Labropoulos, P, Offringa, A, Pandey, VN, Schaye, J, Thomas, RM, Yatawatta, S & Mellema, G 2009, 'Non-parametric foreground subtraction for 21-cm epoch of reionization experiments', Monthly Notices of the Royal Astronomical Society, vol. 397, no. 2, pp. 1138-1152. https://doi.org/10.1111/j.1365-2966.2009.15081.x

Standard

Non-parametric foreground subtraction for 21-cm epoch of reionization experiments. / Harker, Geraint; Zaroubi, Saleem; Bernardi, Gianni; Brentjens, Michiel A.; de Bruyn, A. G.; Ciardi, Benedetta; Jelic, Vibor; Koopmans, Leon V. E.; Labropoulos, Panagiotis; Offringa, Andre; Pandey, V. N.; Schaye, Joop; Thomas, Rajat M.; Yatawatta, Sarod; Mellema, G.

In: Monthly Notices of the Royal Astronomical Society, Vol. 397, No. 2, 01.08.2009, p. 1138-1152.

Research output: Contribution to journalArticleAcademicpeer-review

Vancouver

Harker G, Zaroubi S, Bernardi G, Brentjens MA, de Bruyn AG, Ciardi B et al. Non-parametric foreground subtraction for 21-cm epoch of reionization experiments. Monthly Notices of the Royal Astronomical Society. 2009 Aug 1;397(2):1138-1152. https://doi.org/10.1111/j.1365-2966.2009.15081.x


BibTeX

@article{834c17b6c6e348b08b10e260bec63f52,
title = "Non-parametric foreground subtraction for 21-cm epoch of reionization experiments",
abstract = "One of the problems facing experiments designed to detect redshifted 21-cm emission from the epoch of reionization (EoR) is the presence of foregrounds which exceed the cosmological signal in intensity by orders of magnitude. While fitting them so that they can be removed, we must be careful to minimize 'overfitting', in which we fit away some of the cosmological signal, and 'underfitting', in which real features of the foregrounds cannot be captured by the fit, polluting the signal reconstruction. We argue that in principle it would be better to fit the foregrounds non-parametrically - allowing the data to determine their shape - rather than selecting some functional form in advance and then fitting its parameters. Non-parametric fits often suffer from other problems, however. We discuss these before suggesting a non-parametric method, Wp smoothing, which seems to avoid some of them.After outlining the principles of Wp smoothing, we describe an algorithm used to implement it. Some useful results for implementing an alternative algorithm are given in an appendix. We apply Wp smoothing to a synthetic data cube for the Low Frequency Array (LOFAR) EoR experiment. This cube includes realistic models for the signal, foregrounds, instrumental response and noise. The performance of Wp smoothing, measured by the extent to which it is able to recover the variance of the cosmological signal and to which it avoids the fitting residuals being polluted by leakage of power from the foregrounds, is compared to that of a parametric fit, and to another non-parametric method (smoothing splines). We find that Wp smoothing is superior to smoothing splines for our application, and is competitive with parametric methods even though in the latter case we may choose the functional form of the fit with advance knowledge of the simulated foregrounds. Finally, we discuss how the quality of the fit is affected by the frequency resolution and range, by the characteristics of the cosmological signal and by edge effects.",
keywords = "methods: statistical, cosmology: theory, diffuse radiation, radio lines: general, 21 CENTIMETER FLUCTUATIONS, COSMIC REIONIZATION, HIGH REDSHIFTS, TOMOGRAPHY, SIMULATIONS, CONSTRAINTS, EMISSION, SIGNALS, MODELS, MAPS",
author = "Geraint Harker and Saleem Zaroubi and Gianni Bernardi and Brentjens, {Michiel A.} and {de Bruyn}, {A. G.} and Benedetta Ciardi and Vibor Jelic and Koopmans, {Leon V. E.} and Panagiotis Labropoulos and Andre Offringa and Pandey, {V. N.} and Joop Schaye and Thomas, {Rajat M.} and Sarod Yatawatta and G. Mellema",
year = "2009",
month = aug,
day = "1",
doi = "10.1111/j.1365-2966.2009.15081.x",
language = "English",
volume = "397",
pages = "1138--1152",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "2",

}

RIS

TY - JOUR

T1 - Non-parametric foreground subtraction for 21-cm epoch of reionization experiments

AU - Harker, Geraint

AU - Zaroubi, Saleem

AU - Bernardi, Gianni

AU - Brentjens, Michiel A.

AU - de Bruyn, A. G.

AU - Ciardi, Benedetta

AU - Jelic, Vibor

AU - Koopmans, Leon V. E.

AU - Labropoulos, Panagiotis

AU - Offringa, Andre

AU - Pandey, V. N.

AU - Schaye, Joop

AU - Thomas, Rajat M.

AU - Yatawatta, Sarod

AU - Mellema, G.

PY - 2009/8/1

Y1 - 2009/8/1

N2 - One of the problems facing experiments designed to detect redshifted 21-cm emission from the epoch of reionization (EoR) is the presence of foregrounds which exceed the cosmological signal in intensity by orders of magnitude. While fitting them so that they can be removed, we must be careful to minimize 'overfitting', in which we fit away some of the cosmological signal, and 'underfitting', in which real features of the foregrounds cannot be captured by the fit, polluting the signal reconstruction. We argue that in principle it would be better to fit the foregrounds non-parametrically - allowing the data to determine their shape - rather than selecting some functional form in advance and then fitting its parameters. Non-parametric fits often suffer from other problems, however. We discuss these before suggesting a non-parametric method, Wp smoothing, which seems to avoid some of them.After outlining the principles of Wp smoothing, we describe an algorithm used to implement it. Some useful results for implementing an alternative algorithm are given in an appendix. We apply Wp smoothing to a synthetic data cube for the Low Frequency Array (LOFAR) EoR experiment. This cube includes realistic models for the signal, foregrounds, instrumental response and noise. The performance of Wp smoothing, measured by the extent to which it is able to recover the variance of the cosmological signal and to which it avoids the fitting residuals being polluted by leakage of power from the foregrounds, is compared to that of a parametric fit, and to another non-parametric method (smoothing splines). We find that Wp smoothing is superior to smoothing splines for our application, and is competitive with parametric methods even though in the latter case we may choose the functional form of the fit with advance knowledge of the simulated foregrounds. Finally, we discuss how the quality of the fit is affected by the frequency resolution and range, by the characteristics of the cosmological signal and by edge effects.

AB - One of the problems facing experiments designed to detect redshifted 21-cm emission from the epoch of reionization (EoR) is the presence of foregrounds which exceed the cosmological signal in intensity by orders of magnitude. While fitting them so that they can be removed, we must be careful to minimize 'overfitting', in which we fit away some of the cosmological signal, and 'underfitting', in which real features of the foregrounds cannot be captured by the fit, polluting the signal reconstruction. We argue that in principle it would be better to fit the foregrounds non-parametrically - allowing the data to determine their shape - rather than selecting some functional form in advance and then fitting its parameters. Non-parametric fits often suffer from other problems, however. We discuss these before suggesting a non-parametric method, Wp smoothing, which seems to avoid some of them.After outlining the principles of Wp smoothing, we describe an algorithm used to implement it. Some useful results for implementing an alternative algorithm are given in an appendix. We apply Wp smoothing to a synthetic data cube for the Low Frequency Array (LOFAR) EoR experiment. This cube includes realistic models for the signal, foregrounds, instrumental response and noise. The performance of Wp smoothing, measured by the extent to which it is able to recover the variance of the cosmological signal and to which it avoids the fitting residuals being polluted by leakage of power from the foregrounds, is compared to that of a parametric fit, and to another non-parametric method (smoothing splines). We find that Wp smoothing is superior to smoothing splines for our application, and is competitive with parametric methods even though in the latter case we may choose the functional form of the fit with advance knowledge of the simulated foregrounds. Finally, we discuss how the quality of the fit is affected by the frequency resolution and range, by the characteristics of the cosmological signal and by edge effects.

KW - methods: statistical

KW - cosmology: theory

KW - diffuse radiation

KW - radio lines: general

KW - 21 CENTIMETER FLUCTUATIONS

KW - COSMIC REIONIZATION

KW - HIGH REDSHIFTS

KW - TOMOGRAPHY

KW - SIMULATIONS

KW - CONSTRAINTS

KW - EMISSION

KW - SIGNALS

KW - MODELS

KW - MAPS

U2 - 10.1111/j.1365-2966.2009.15081.x

DO - 10.1111/j.1365-2966.2009.15081.x

M3 - Article

VL - 397

SP - 1138

EP - 1152

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -

ID: 4924441