311 citations · 1.5k across the 29 of their papers we have counts for
27 papers
The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
S. Ghosh, L. V. E. Koopmans, C. Brinkerink +17
The Dark Ages (DA) provides a crucial window into the physics of the infant Universe, with the 21-cm signal offering the only direct probe for mapping out the three-dimensional dis…
Square Kilometre Array Science Data Challenge 3a: foreground removal for an EoR experiment
A. Bonaldi, P. Hartley, R. Braun +179
We present and analyse the results of the Science data challenge 3a (SDC3a, https://sdc3.skao.int/challenges/foregrounds), an EoR foreground-removal community-wide exercise organis…
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…
Mitigating calibration errors from mutual coupling with time-domain filtering of 21 cm cosmological radio observations
N. Charles, N. S. Kern, R. Pascua +80
The 21 cm transition from neutral Hydrogen promises to be the best observational probe of the Epoch of Reionisation (EoR). This has led to the construction of low-frequency radio i…
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…
A novel radio imaging method for physical spectral index modelling
E. Ceccotti, A. R. Offringa, L. V. E. Koopmans +9
We present a new method, called "forced-spectrum fitting", for physically-based spectral modelling of radio sources during deconvolution. This improves upon current common deconvol…
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…
Degree-Scale Galactic Radio Emission at 122 MHz around the North Celestial Pole with LOFAR-AARTFAAC
B. K. Gehlot, L. V. E. Koopmans, A. R. Offringa +11
Aims: Contamination from bright diffuse Galactic thermal and non-thermal radio emission poses crucial challenges in experiments aiming to measure the 21-cm signal of neutral hydrog…
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…
Characterization of the AARTFAAC-12 aperture array: radio source counts at 42 and 61 MHz
A. Shulevski, T. M. O. Franzen, W. L. Williams +4
Dense aperture arrays provide key benefits in modern astrophysical research. They are flexible, employing cheap receivers, while relying on the ever more sophisticated compute back…
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…
Precision requirements for interferometric gridding in 21-cm power spectrum analysis
A. R. Offringa, F. Mertens, S. van der Tol +4
We analyse the accuracy of radio interferometric gridding of visibilities with the aim to quantify the Epoch of Reionization (EoR) 21-cm power spectrum bias caused by gridding, ult…