307 citations · 5.5k across the 80 of their papers we have counts for
80 papers
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…
Upper limits on the 21-cm Epoch of Reionization power spectrum from one night with LOFAR
A. H. Patil, S. Yatawatta, L. V. E. Koopmans +25
We present the first limits on the Epoch of Reionization (EoR) 21-cm HI power spectra, in the redshift range , using the Low-Frequency Array (LOFAR) High-Band Antenna (…
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…
Wide-field LOFAR imaging of the field around the double-double radio galaxy B1834+620: A fresh view on a restarted AGN and doubeltjes
E. Orrú, S. van Velzen, R. F. Pizzo +8
The existence of double-double radio galaxies (DDRGs) is evidence for recurrent jet activity in AGN, as expected from standard accretion models. A detailed study of these rare sour…
Linear polarization structures in LOFAR observations of the interstellar medium in the 3C196 field
V. Jelić, A. G. de Bruyn, V. N. Pandey +21
This study aims to characterize linear polarization structures in LOFAR observations of the interstellar medium (ISM) in the 3C196 field, one of the primary fields of the LOFAR-Epo…
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…
Galactic interstellar filaments as probed by LOFAR and Planck
S. Zaroubi, V. Jelić, A. G. de Bruyn +13
Recent Low Frequency Array (LOFAR) observations at 115-175 MHz of a field at medium Galactic latitudes (centered at the bright quasar 3C196) have shown striking filamentary structu…
The Cosmic Dawn and Epoch of Reionization with the Square Kilometre Array
L. V. E. Koopmans, J. Pritchard, G. Mellema +42
Concerted effort is currently ongoing to open up the Epoch of Reionization (EoR) (15-6) for studies with IR and radio telescopes. Whereas IR detections have been made of sou…
Simulating the 21cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
B. Ciardi, S. Inoue, F. B. Abdalla +26
We investigate the feasibility of detecting 21cm absorption features in the afterglow spectra of high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations of c…
Polarization leakage in Epoch of Reionization windows: I. LOFAR observations of the 3C196 field
K. M. B. Asad, L. V. E. Koopmans, V. Jelić +25
Detection of the 21-cm signal coming from the epoch of reionization (EoR) is challenging especially because, even after removing the foregrounds, the residual Stokes maps conta…
The intra-hour variable quasar J18193845: 13-year evolution, jet polarization structure and interstellar scattering screen properties
A. G. de Bruyn, J. -P. Macquart
We examine the long-term evolution of the intra-hour variable quasar, J1819+3845, whose variations have been attributed to interstellar scintillation by extremely local turbulent p…
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…
Initial LOFAR observations of Epoch of Reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field
V. Jelic, A. G. de Bruyn, M. Mevius +106
This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal…
A Comprehensive Radio View of the Extremely Bright Gamma-Ray Burst 130427A
A. J. van der Horst, Z. Paragi, A. G. de Bruyn +11
GRB 130427A was extremely bright as a result of occurring at low redshift whilst the energetics were more typical of high-redshift gamma-ray bursts (GRBs). We collected well-sample…
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…
Constraining the epoch of reionization with the variance statistic: simulations of the LOFAR case
Ajinkya H. Patil, Saleem Zaroubi, Emma Chapman +27
Several experiments are underway to detect the cosmic redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise rati…
The spin temperature of high-redshift damped Lyman- systems
N. Kanekar, J. X. Prochaska, A. Smette +10
We report results from a programme aimed at investigating the temperature of neutral gas in high-redshift damped Lyman- absorbers (DLAs). This involved (1) HI 21cm absorption st…
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 (…
The brightness and spatial distributions of terrestrial radio sources
A. R. Offringa, A. G. de Bruyn, S. Zaroubi +75
Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obs…
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…
Probing reionization with LOFAR using 21-cm redshift space distortions
Hannes Jensen, Kanan K. Datta, Garrelt Mellema +24
One of the most promising ways to study the epoch of reionization (EoR) is through radio observations of the redshifted 21-cm line emission from neutral hydrogen. These observation…