311 citations · 1.5k across the 29 of their papers we have counts for
18 papers · 1 filter
Spectral modelling of Cygnus A between 110 and 250 MHz. Impact on the LOFAR 21-cm signal power spectrum
E. Ceccotti, A. R. Offringa, L. V. E. Koopmans +15
Studying the redshifted 21-cm signal from the the neutral hydrogen during the Epoch of Reionization and Cosmic Dawn is fundamental for understanding the physics of the early univer…
Ionospheric contributions to the excess power in high-redshift 21-cm power-spectrum observations with LOFAR
S. A. Brackenhoff, M. Mevius, L. V. E. Koopmans +9
The turbulent ionosphere causes phase shifts to incoming radio waves on a broad range of temporal and spatial scales. When an interferometer is not sufficiently calibrated for the…
The impact of lossy data compression on the power spectrum of the high redshift 21-cm signal with LOFAR
J. K. Chege, L. V. E. Koopmans, A. R. Offringa +8
Current radio interferometers output multi-petabyte-scale volumes of data per year making the storage, transfer, and processing of this data a sizeable challenge. This challenge is…
Beyond the horizon: Quantifying the full sky foreground wedge in the cylindrical power spectrum
S. Munshi, F. G. Mertens, L. V. E. Koopmans +8
One of the main obstacles preventing the detection of the redshifted 21-cm signal from neutral hydrogen in the early Universe is the astrophysical foreground emission, which is sev…
Investigating Mutual Coupling in the Hydrogen Epoch of Reionization Array and Mitigating its Effects on the 21-cm Power Spectrum
E. Rath, R. Pascua, A. T. Josaitis +78
Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on the 21-cm power spectrum…
Transient RFI environment of LOFAR-LBA at 72-75 MHz: Impact on ultra-widefield AARTFAAC Cosmic Explorer observations of the redshifted 21-cm signal
B. K. Gehlot, L. V. E. Koopmans, S. A. Brackenhoff +13
Measurement of the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn (CD) and Epoch of Reionisation (EoR) promises to unveil a wealth of information about the astrop…
First upper limits on the 21 cm signal power spectrum from cosmic dawn from one night of observations with NenuFAR
S. Munshi, F. G. Mertens, L. V. E. Koopmans +24
The redshifted 21 cm signal from neutral hydrogen is a direct probe of the physics of the early universe and has been an important science driver of many present and upcoming radio…
Diffuse Sources, Clustering and the Excess Anisotropy of the Radio Synchrotron Background
F. J. Cowie, A. R. Offringa, B. K. Gehlot +4
We present the largest low frequency (120~MHz) arcminute resolution image of the radio synchrotron background (RSB) to date, and its corresponding angular power spectrum of anisotr…
Assessing the impact of two independent direction-dependent calibration algorithms on the LOFAR 21-cm signal power spectrum
H. Gan, F. G. Mertens, L. V. E. Koopmans +11
Detecting the 21-cm signal from the Epoch of Reionisation (EoR) is challenging due to the strong astrophysical foregrounds, ionospheric effects, radio frequency interference and in…
Statistical analysis of the causes of excess variance in the 21 cm signal power spectra obtained with the Low-Frequency Array
H. Gan, L. V. E Koopmans, F. G. Mertens +11
The detection of the 21 cm signal of neutral hydrogen from the Epoch of Reionization (EoR) is challenging due to bright foreground sources, radio frequency interference (RFI), the…
Precision Calibration of Radio Interferometers for 21 cm Cosmology with No Redundancy and Little Knowledge of Antenna Beams and the Radio Sky
Aaron Ewall-Wice, Joshua S. Dillon, Bharat Gehlot +3
We introduce CALAMITY, a precision bandpass calibration method for radio interferometry. CALAMITY can solve for direction independent gains with arbitrary frequency structure to th…
A numerical study of 21-cm signal suppression and noise increase in direction-dependent calibration of LOFAR data
M. Mevius, F. Mertens, L. V. E. Koopmans +14
We investigate systematic effects in direction dependent gain calibration in the context of the Low-Frequency Array (LOFAR) 21-cm Epoch of Reionization (EoR) experiment. The LOFAR…
Comparing Foreground Removal Techniques for Recovery of the LOFAR-EoR 21cm Power Spectrum
Ian Hothi, Emma Chapman, Jonathan R. Pritchard +10
We compare various foreground removal techniques that are being utilised to remove bright foregrounds in various experiments aiming to detect the redshifted 21cm signal of neutral…
The AARTFAAC Cosmic Explorer: observations of the 21-cm power spectrum in the EDGES absorption trough
B. K. Gehlot, F. G. Mertens, L. V. E. Koopmans +12
The 21-cm absorption feature reported by the EDGES collaboration is several times stronger than that predicted by traditional astrophysical models. If genuine, a deeper absorption…
Tight Constraints on the Excess Radio Background at from LOFAR
R. Mondal, A. Fialkov, C. Fling +13
The ARCADE2 and LWA1 experiments have claimed an excess over the Cosmic Microwave Background (CMB) at low radio frequencies. If the cosmological high-redshift contribution to this…
Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at from LOFAR
F. G. Mertens, M. Mevius, L. V. E Koopmans +23
A new upper limit on the 21-cm signal power spectrum at a redshift of is presented, based on 141 hours of data obtained with the Low-Frequency Array (LOFAR). The an…
Constraining the intergalactic medium at 9.1 using LOFAR Epoch of Reionization observations
R. Ghara, S. K. Giri, G. Mellema +19
We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift 9.1 using new upper limits on the 21-cm power spectrum measured b…
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 (…