307 citations · 5.5k across the 80 of their papers we have counts for
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Wide-field LOFAR-LBA power-spectra analyses: Impact of calibration, polarization leakage and ionosphere
B. K. Gehlot, L. V. E. Koopmans, A. G. de Bruyn +9
Contamination due to foregrounds (Galactic and Extra-galactic), calibration errors and ionospheric effects pose major challenges in detection of the cosmic 21 cm signal in various…
Polarization leakage in epoch of reionization windows: III. Wide-field effects of narrow-field arrays
K. M. B. Asad, L. V. E. Koopmans, V. Jelić +3
Leakage of polarized Galactic diffuse emission into total intensity can potentially mimic the 21-cm signal coming from the epoch of reionization (EoR), as both of them might have f…
Probing Ionospheric Structures using the LOFAR radio telescope
M. Mevius, S. van der Tol, V. N. Pandey +24
LOFAR is the LOw Frequency Radio interferometer ARray located at mid-latitude (). Here, we present results on ionospheric structures derived from 29 LOFAR nighttim…
Systematic biases in low frequency radio interferometric data due to calibration: the LOFAR EoR case
Ajinkya H. Patil, Sarod Yatawatta, Saleem Zaroubi +8
The redshifted 21 cm line of neutral hydrogen is a promising probe of the Epoch of Reionization (EoR). However, its detection requires a thorough understanding and control of the s…
Polarization leakage in epoch of reionization windows: II. Primary beam model and direction dependent calibration
K. M. B. Asad, L. V. E. Koopmans, V. Jelić +11
Leakage of diffuse polarized emission into Stokes I caused by the polarized primary beam of the instrument might mimic the spectral structure of the 21-cm signal coming from the ep…
The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results
G. H. Heald, R. F. Pizzo, E. Orrú +147
We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and de…
Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz
H. K. Vedantham, L. V. E. Koopmans, A. G. de Bruyn +91
We present radio observations of the Moon between and MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far bey…
Calibration artefacts in radio interferometry. I. Ghost sources in WSRT data
T. G. Grobler, C. D. Nunhokee, O. M. Smirnov +2
This work investigates a particular class of artefacts, or ghost sources, in radio interferometric images. Earlier observations with (and simulations of) the Westerbork Synthesis R…
LOFAR imaging capabilities and system sensitivity
R. J. Nijboer, M. Pandey-Pommier, A. G. de Bruyn
This document describes the general astronomical capabilities of the LOw Frequency ARray (LOFAR). The frequency range covered by LOFAR is split into two bands denoted as low band (…
Chromatic effects in the 21 cm global signal from the cosmic dawn
H. K. Vedantham, L. V. E. Koopmans, A. G. de Bruyn +3
The redshifted 21 cm brightness distribution from neutral hydrogen is a promising probe into the cosmic dark ages, cosmic dawn, and re-ionization. LOFAR's Low Band Antennas (LBA) m…
Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole
S. Yatawatta, A. G. de Bruyn, M. A. Brentjens +86
The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitu…
Post-correlation filtering techniques for off-axis source and RFI removal
A. R. Offringa, A. G. de Bruyn, S. Zaroubi
Techniques to improve the data quality of interferometric radio observations are considered. Fundaments of fringe frequencies in the uv-plane are discussed and filters are used to…
MeqTrees and direction-dependent effects
O. M. Smirnov, A. G. de Bruyn
Direction-dependent effects (DDEs) represent a major challenge both for calibration of new radio telescopes, and for advancing the state of the art of existing ones. Various approa…
Observing pulsars and fast transients with LOFAR
B. W. Stappers, J. W. T. Hessels, A. Alexov +91
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…
Radio Interferometric Calibration Using The SAGE Algorithm
S. Kazemi, S. Yatawatta, S. Zaroubi +3
The aim of the new generation of radio synthesis arrays such as LOFAR and SKA is to achieve much higher sensitivity, resolution and frequency coverage than what is available now, e…