Foreground simulations for the LOFAR-epoch of reionization experiment

Jelić, Vibor; Zaroubi, Saleem; Labropoulos, P.; Thomas, Rajat Mani; Bernardi, G.; Brentjens, M. A.; Bruyn, de Antonius; Ciardi, B.; Harker, G.; Koopmans, L. V. E.; Pandey, V. N.; Schaye, Joop; Yatawatta, S.

doi:10.1111/j.1365-2966.2008.13634.x

Cited by 280 publications

(399 citation statements)

References 63 publications

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“…The EoR power spectrum can be observed over about two orders of magnitude in wave numbers and other higher-order statistical measures can be obtained as well (Jelić et al 2008;Harker et al 2009Harker et al , 2010Labropoulos et al 2009). It might even be possible to image the EoR as it unfolds on very large scales after several thousand hours of integration time on a single field (Zaroubi et al 2012).…”

Section: Epoch Of Reionizationmentioning

confidence: 94%

LOFAR: The LOw-Frequency ARray

Haarlem

Wise

Gunst

et al. 2013

A&A

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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: Epoch Of Reionizationmentioning

confidence: 94%

LOFAR: The LOw-Frequency ARray

Haarlem

Wise

Gunst

et al. 2013

A&A

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2,096

783

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“…At low frequencies, thermal absorption adds to depolarization effects and must be properly taken into account. LOFAR will make a major attempt to trace the very weak signal from the Epoch of reionization, where the selection of a highlatitude Galactic area with very low foreground signal is important for the success of these ambitious low-frequency observations as well as the subtraction of all kinds of extragalactic foregrounds as discussed by Jelić et al (2008 …”

Section: Discussionmentioning

confidence: 99%

Simulated square kilometre array maps from Galactic 3D-emission models

Sun¹,

Reich²

2009

A&A

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Context. Planning of the Square Kilometre Array (SKA) requires simulations of the expected sky emission at arcsec angular resolution to evaluate its scientific potential, to constrain its technical realization in the best possible way, and to guide the observing strategy. Aims. We simulate high-resolution total intensity, polarization, and rotation measure (RM) maps of selected fields based on our recent global 3D-model of Galactic emission.Methods. Simulations of diffuse Galactic emission were conducted using the hammurabi code modified for arcsec angular resolution patches towards various Galactic directions. The random magnetic field components are set to follow a Kolmogorov-like power-law spectrum. We analysed the simulated maps in terms of their probability density functions (PDFs) and structure functions.Results. We present maps for various Galactic longitudes and latitudes at 1.4 GHz, which is the frequency where deep SKA surveys are proposed. The maps are about 1.• 5 in size and have an angular resolution of about 1. 6. Total intensity emission is smoother in the plane than at high latitudes because of the different contributions from the regular and random magnetic field. The high-latitude fields show more extended polarized emission and RM structures than those in the plane, where patchy emission structures dominate on very small scales. The RM PDFs in the plane are close to Gaussians, but clearly deviate from that at high latitudes. The RM structure functions show smaller amplitudes and steeper slopes towards high latitudes. These results emerge from much more turbulent cells being passed through by the line-of-sights in the plane. Although the simulated random magnetic field components distribute in 3D, the magnetic field spectrum extracted from the structure functions of RMs conforms to 2D in the plane and approaches 3D at high latitudes. This is partly related to the outer scale of the turbulent magnetic field, but mainly to the different lengths of the lines-ofsight. Conclusions. The significant scatter of the simulated RM distributions agrees with the large scatter of observed RMs of pulsars and extragalactic sources in the Galactic plane and also at high Galactic latitudes. A very dense grid of RMs from extragalactic sources is required to trace and separate Galactic RM foreground fluctuations. Even at high latitudes, total intensity and polarized emission is highly structured, which will contaminate sensitive high-resolution extragalactic observations with the SKA and have to be separated in an appropriate way.

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“…is expected that if the foregrounds are smooth enough along the frequency direction, they can be simply removed by fitting out a smooth function (Jelić et al 2008;Morales et al 2006;Santos et al 2005). In this analysis we assume that foreground cleaning was applied on a region of 32 MHz (so as to avoid edge effects on our 4 MHz interval) and was successful on scales smaller than this 32 MHz, e.g.…”

Section: Methodsmentioning

confidence: 99%

Probing the first galaxies with the Square Kilometer Array

Santos

Silva

Pritchard

et al. 2011

A&A

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Observations of anisotropies in the brightness temperature of the 21 cm line of neutral hydrogen from the period before reionization would shed light on the dawn of the first stars and galaxies. In this paper, we use large-scale semi-numerical simulations to analyse the imprint on the 21 cm signal of spatial fluctuations in the Lyman-α flux arising from the clustering of the first galaxies. We show that an experiment such as the Square Kilometer Array (SKA) can probe this signal at the onset of reionization, giving us important information about the UV emission spectra of the first stars and characterizing their host galaxies. SKA-pathfinders with ∼10% of the full collecting area should be capable of making a statistical detection of the 21 cm power spectrum at redshifts z < ∼ 20 (corresponding to frequencies ν > ∼ 67 MHz). We then show that the SKA should be able to measure the three dimensional power spectrum as a function of the angle with the line of sight and discuss the use of the redshift space distortions as a way to separate out the different components of the 21 cm power spectrum. We demonstrate that, at least on large scales where the Lyα fluctuations are linear, they can be used as a model independent way to extract the power spectra due to these Lyα fluctuations.

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Foreground simulations for the LOFAR-epoch of reionization experiment

Cited by 280 publications

References 63 publications

LOFAR: The LOw-Frequency ARray

LOFAR: The LOw-Frequency ARray

Simulated square kilometre array maps from Galactic 3D-emission models

Probing the first galaxies with the Square Kilometer Array

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