The Long Wavelength Array

Ellingson, S.W.; Clarke, T. E.; Cohen, A. S.; Craig, John L.; Kassim, N. E.; Pihlström, Y. M.; Rickard, L. J.; Taylor, G. B.

doi:10.1109/jproc.2009.2015683

Cited by 180 publications

(157 citation statements)

References 27 publications

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“…The discovery of the giant and A&A 509, A68 (2010) ultra-steep spectrum radio halo in Abell 521 at low radio frequencies ) allows a first confirmation of this conjecture and provides a glimpse of what future low frequency radio telescopes, such as the Low Frequency Array (LOFAR) 1 and the Long Wavelength Array (LWA, e.g., Ellingson et al 2009), might find in upcoming years.…”

Section: Introductionmentioning

confidence: 91%

Unveiling radio halos in galaxy clusters in the LOFAR era

Cassano¹,

Brunetti²,

Röttgering

et al. 2009

A&A

132

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Aims. Giant radio halos are mega-parsec scale synchrotron sources detected in a fraction of massive and merging galaxy clusters. Radio halos provide one of the most important pieces of evidence of non-thermal components in large-scale structure. Statistics of their properties can be used to discriminate among various models for their origin. Therefore, theoretical predictions of the occurrence of radio halos are important as several new radio telescopes are about to begin to survey the sky at low frequencies with unprecedented sensitivity. Methods. We carry out Monte Carlo simulations to model the formation and evolution of radio halos in a cosmological framework. In the context of the turbulent re-acceleration model, we extend previous work on the statistical properties of radio halos. Results. We first compute the fraction of galaxy clusters that show radio halos and derive the luminosity function of the radio halos. We then derive differential and integrated number count distributions of radio halos at low radio frequencies to explore the potential of the upcoming LOFAR surveys. By restricting ourselves to clusters at redshifts <0.6, we find that the planned LOFAR all-sky survey at 120 MHz is expected to detect about 350 giant radio halos. About half of these halos have spectral indices greater than 1.9 and brighten substantially at lower frequencies. If detected they will enable us to confirm that turbulence accelerates the emitting particles. We also propose that commissioning surveys, such as MS 3 , have the potential to detect about 60 radio halos in clusters of the ROSAT brightest cluster sample and its extension (eBCS). These surveys will allow us to constrain how the rate of formation of radio halos in these clusters depends on cluster mass.

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Section: Introductionmentioning

confidence: 91%

Unveiling radio halos in galaxy clusters in the LOFAR era

Cassano¹,

Brunetti²,

Röttgering

et al. 2009

A&A

132

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“…LOFAR can have up to a total of 244 station beams which equals the number of subbands. The Long Wavelength Array (LWA) (Ellingson et al 2009) collecting area is quoted for a frequency of 20 MHz and decreases as λ 2 . We note that the LWA and MWA collecting areas are those projected for the final system and are not yet in place.…”

Section: Lofarmentioning

confidence: 99%

Observing pulsars and fast transients with LOFAR

Stappers

Hessels

Alexov

et al. 2011

A&A

215

160

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Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR.

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“…Due to funding constraints, the original collaboration split in 2004 resulting in three currently ongoing low-frequency array development projects: the European LOFAR project described here; the US-led, Long Wavelength Array (LWA; Ellingson et al 2009Ellingson et al , 2013; and the international Murchison Widefield Array (MWA) collaboration (Lonsdale et al 2009;Tingay et al 2013a).…”

Section: Introductionmentioning

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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The Long Wavelength Array

Cited by 180 publications

References 27 publications

Unveiling radio halos in galaxy clusters in the LOFAR era

Unveiling radio halos in galaxy clusters in the LOFAR era

Observing pulsars and fast transients with LOFAR

LOFAR: The LOw-Frequency ARray

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