The Precision Array for Probing the Epoch of Re-Ionization: Eight Station Results

Parsons, Aaron; Backer, D. C.; Foster, Griffin; Wright, M. C. H.; Bradley, Richard F.; Gugliucci, Nicole E.; Parashare, Chaitali; Benoit, E.; Aguirre, James E.; Jacobs, Daniel; Carilli, C. L.; Herne, D.; Lynch, M. J.; Manley, Jason; Werthimer, D.

doi:10.1088/0004-6256/139/4/1468

Cited by 446 publications

(340 citation statements)

References 26 publications

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“…Besides LOFAR itself, these new instruments include the recently commissioned LWA (10−88 MHz) (see Kassim et al 2010;Lazio et al 2010;Taylor et al 2012, and examples therein) and MWA (80−300 MHz) (see Rightley et al 2009;Oberoi et al 2011;Bowman et al 2013;Tingay et al 2013b, and examples therein), both of which provide powerful solar observing capabilities. Although not specficially intended for solar observations, the PAPER (see Parsons et al 2010;Stefan et al 2013;Pober et al 2013, for descriptions of the PAPER instrument) operates in the 100−200 MHz range and also provides similar potential capablities. In the Ukraine, the radio telescopes UTR2 (Sidorchuk et al 2005) and URAN2 (Brazhenko et al 2005) also work at low frequencies.…”

Section: Solar Physics and Space Weathermentioning

confidence: 99%

LOFAR: The LOw-Frequency ARray

Haarlem

Wise

Gunst

et al. 2013

A&A

2,096

783

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LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory.

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Section: Solar Physics and Space Weathermentioning

confidence: 99%

LOFAR: The LOw-Frequency ARray

Haarlem

Wise

Gunst

et al. 2013

A&A

2,096

783

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“…To date, a number of experiments have sought to measure this high-redshift 21 cm emission, using LOFAR (van Haarlem et al 2013), the GMRT (Paciga et al 2011), the MWA Tingay et al 2013), PAPER (Parsons et al 2010), and the 21CMA (Zheng et al 2016). These experiments are designed to detect the cosmological 21 cm signal through a number of statistical measures of its brightness-temperature fluctuations, such as its variance (e.g., Patil et al 2014;Watkinson & Pritchard 2014) and its power spectrum as a function of redshift (e.g., Morales & Hewitt 2004;Barkana & Loeb 2005;Bharadwaj & Ali 2005;Bowman et al 2006;McQuinn et al 2006;Pritchard & Furlanetto 2007;Jelić et al 2008; Pritchard & Loeb 2008;Harker et al 2009Harker et al , 2010).…”

Section: Introductionmentioning

confidence: 99%

Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR

Patil

Yatawatta

Koopmans

et al. 2017

ApJ

291

374

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We present the first limits on the Epoch of Reionization 21 cm H I power spectra, in the redshift range z=7.9-10.6, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total, 13.0 hr of data were used from observations centered on the North Celestial Pole. After subtraction of the sky model and the noise bias, we detect a non-zero 56 13 mK D < ( ) at k=0.053 h cMpc −1 in the range z=9.6-10.6. The excess variance decreases when optimizing the smoothness of the direction-and frequency-dependent gain calibration, and with increasing the completeness of the sky model. It is likely caused by (i) residual side-lobe noise on calibration baselines, (ii) leverage due to nonlinear effects, (iii) noise and ionosphere-induced gain errors, or a combination thereof. Further analyses of the excess variance will be discussed in forthcoming publications.

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“…However, a statistical detection of the 21 cm reionization signal through power-spectrum analysis should be possible with ∼0.1% of a square kilometer of collecting area. Many first-generation experiments aiming to measure the 21 cm power spectrum are under construction or already observing, including the Giant Metre-wave Radio Telescope (GMRT; Pen et al 2009), 5 the Low Frequency Array (LOFAR; Rottgering et al 2006), 6 the Murchison Widefield Array (MWA; Lonsdale et al 2009), 7 5 http://gmrt.ncra.tifr.res.in/ 6 http://www.lofar.org/ 7 http://www.mwatelescope.org/ and the Precision Array for Probing the Epoch of Reionization (PAPER; Parsons et al 2010). 8 An interferometer accesses the three-dimensional power spectrum of 21 cm EoR emission by measuring variation perpendicular to the line of sight using samples provided by different baselines in the uv-plane, and variation parallel to the line of sight using the Fourier transform of frequency data (Morales 2005).…”

Section: Introductionmentioning

confidence: 99%

A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE

Parsons

Pober

Aguirre

et al. 2012

ApJ

Self Cite

303

458

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A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons & Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this technique substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK 2 near k ∼ 0.2 h Mpc −1 with 132 dipoles in 7 months of observing.

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The Precision Array for Probing the Epoch of Re-Ionization: Eight Station Results

Cited by 446 publications

References 26 publications

LOFAR: The LOw-Frequency ARray

LOFAR: The LOw-Frequency ARray

Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR

A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE

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