Explanipedia

Scalable and robust wide-field facet calibration with LOFAR’s longest baselines Open

J. M. G. H. J. de Jong, L. Veefkind, R. J. van Weeren, J. B. R. Oonk, R. J. Schlimbach , et al. · 2025

Recent work has successfully achieved subarcsecond wide-field imaging with high-band observations from the LOw Frequency ARray (LOFAR). However, the scalability of this work remains limited due to the need for manual intervention, poor cal…

Unlocking ultra-deep wide-field imaging with sidereal visibility averaging Open

J. M. G. H. J. de Jong, R. J. van Weeren, Tammo Jan Dijkema, J. B. R. Oonk, H. J. A. Röttgering , et al. · 2025

Producing ultra-deep high-angular-resolution images with current and next-generation radio interferometers introduces significant computational challenges. In particular, the imaging is so demanding that processing large datasets, accumula…

Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images Open

J. M. G. H. J. de Jong, R. J. van Weeren, Frits Sweijen, J. B. R. Oonk, T. W. Shimwell , et al. · 2024

We present the deepest wide-field 115–166 MHz image at sub-arcsecond resolution spanning an area of 2.5° × 2.5° centred at the ELAIS-N1 deep field. To achieve this, we improved the direction-independent (DI) and direction-dependent (DD) ca…

Into the depths: Unveiling ELAIS-N1 with LOFAR's deepest sub-arcsecond wide-field images Open

J. M. G. H. J. de Jong, R. J. van Weeren, Frits Sweijen, J. B. R. Oonk, T. W. Shimwell , et al. · 2024

We present the deepest wide-field 115-166 MHz image at sub-arcsecond resolution spanning an area of 2.5 by 2.5 degrees centred at the ELAIS-N1 deep field. To achieve this, we improved the calibration for the International LOFAR Telescope. …

The LOFAR Two-metre Sky Survey: I. Survey description and preliminary data release Open

T. W. Shimwell, H. J. A. Röttgering, P. N. Best, W. L. Williams, Tammo Jan Dijkema , et al. · 2024

The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120–168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ~5″ …

Cosmic evolution of FRI and FRII sources out to <i>z</i> = 2.5 Open

J. M. G. H. J. de Jong, H. J. A. Röttgering, R. Kondapally, B. Mingo, R. J. van Weeren , et al. · 2023

Context. Radio-loud active galactic nuclei (RLAGN) play an important role in the evolution of galaxies through the effects on their environment. The two major morphological classes are core-bright (FRI) and edge-bright (FRII) sources. With…

Cosmic evolution of FRI and FRII sources out to z=2.5 Open

J. M. G. H. J. de Jong, H. J. A. Röttgering, R. Kondapally, B. Mingo, R. J. van Weeren , et al. · 2023

Radio-loud active galactic nuclei (RLAGN) play an important role in the evolution of galaxies through the effects on their environment. The two major morphological classes are core-bright (FRI) and edge-bright (FRII) sources. With the LOw-…

An open compute and data federation as an alternative to monolithic infrastructures for big Earth data analytics Open

Björn Backeberg, Zdeněk Šustr, Enol Fernández, ‪Gennadii Donchyts, Arjen Haag , et al. · 2022

An adequate compute and storage infrastructure supporting the full exploitation of Copernicus and Earth Observation datasets is currently not available in Europe. This paper presents the cross-disciplinary open-source technologies being le…

Deep sub-arcsecond wide-field imaging of the Lockman Hole field at 144 MHz Open

Frits Sweijen, R. J. van Weeren, H. J. A. Röttgering, L. K. Morabito, N. Jackson , et al. · 2022

The LOFAR Two-metre Sky Survey Open

T. W. Shimwell, M. J. Hardcastle, C. Tasse, P. N. Best, H. J. A. Röttgering , et al. · 2022

In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120–168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44°30′ and 1h00m…

Deep study of A399-401: application of a wide-field facet calibration Open

J. M. G. H. J. de Jong, R. J. van Weeren, A. Botteon, J. B. R. Oonk, G. Brunetti , et al. · 2022

We examine the particle acceleration mechanism in the Mpc-scale bridge between Abell 399 and Abell 401 and assess in particular if the synchrotron emission originates from first-order or second-order Fermi re-acceleration. We use deep (~40…

Arecibo-Green Bank-LOFAR Carbon Radio Recombination Line Observations toward Cold H i Clouds Open

D. Anish Roshi, Wendy Peters, K. L. Emig, P. Salas, J. B. R. Oonk , et al. · 2022

We present results from a search for radio recombination lines in three H i self-absorbing (HISA) clouds at 750 MHz and 321 MHz with the Robert C. Byrd Green Bank Telescope, and in three Galactic plane positions at 327 MHz with the Arecibo…

Arecibo-Green Bank-LOFAR Carbon Radio Recombination Line observations toward cold HI Clouds Open

D. Anish Roshi, Wendy Peters, K. L. Emig, Philip W. Salas, J. B. R. Oonk , et al. · 2021

We present results from a search for radio recombination lines in three HI self-absorbing (HISA) clouds at 750 MHz and 321 MHz with the Robert C. Byrd Green Bank Telescope (GBT), and in three Galactic Plane positions at 327 MHz with the Ar…

Taking snapshots of the jet-ISM interplay: The case of PKS0023-26 Open

R. Morganti, Tom Oosterloo, C. N. Tadhunter, E. Bernhard, J. B. R. Oonk · 2021

We present high angular resolution ALMA CO(2-1) and 1.7 mm continuum observations of the far-infrared-bright galaxy PKS0023-26, which hosts a young radio source and a luminous optical AGN. Although young, the powerful radio source has grow…

Taking snapshots of the jet-ISM interplay: The case of PKS 0023–26 Open

R. Morganti, Tom Oosterloo, C. N. Tadhunter, E. Bernhard, J. B. R. Oonk · 2021

We present high angular resolution (0.13–0.4 arcsec) ALMA CO(2–1) and 1.7 mm continuum observations of the far-infrared-bright galaxy PKS 0023−26 ( z = 0.32), which hosts a young radio source as well as a luminous optical active galactic n…

Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline Open

L. K. Morabito, N. Jackson, S. Mooney, Frits Sweijen, Shruti Badole , et al. · 2021

[abridged] The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2,000 km, LOFAR has the unique capability of achieving sub-arcsecond resolution at frequencies below 200 MHz, al…

Sub-arcsecond imaging with the International LOFAR Telescope Open

L. K. Morabito, N. Jackson, S. Mooney, Frits Sweijen, Shruti Badole , et al. · 2021

The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2000 km, LOFAR has the unique capability of achieving sub-arcsecond resolution at frequencies below 200 MHz. However, it is…

A compact core-jet structure in the changing-look Seyfert NGC 2617 Open

Jun Yang, Z. Paragi, R. J. Beswick, Wen Chen, Ilse van Bemmel , et al. · 2021

The nearby face-on spiral galaxy NGC 2617 underwent an unambiguous ‘inside–out’ multiwavelength outburst in Spring 2013, and a dramatic Seyfert-type change probably between 2010 and 2012, with the emergence of broad optical emission lines.…

A parsec-scale faint jet in the nearby changing-look Seyfert galaxy Mrk 590 Open

Jun Yang, Ilse van Bemmel, Z. Paragi, S. Komossa, Ye‐Fei Yuan , et al. · 2021

Broad Balmer emission lines in active galactic nuclei (AGN) may display dramatic changes in amplitude, even disappearance and re-appearance in some sources. As a nearby galaxy at a redshift of z = 0.0264, Mrk 590 suffered such a cycle of S…

A molecular absorption line survey towards the AGN of Hydra-A Open

Tom Rose, A. C. Edge, F. Combes, S. Hamer, B. R. McNamara , et al. · 2020

We present Atacama Large Millimetre/submillimetre Array observations of the brightest cluster galaxy Hydra-A, a nearby (z = 0.054) giant elliptical galaxy with powerful and extended radio jets. The observations reveal CO(1−0), CO(2–1), 13C…

Pioneering the Exascale era with Astronomy Open

J. B. R. Oonk, C. Schrijvers, Y. van den Berg · 2020

SURF is the collaborative ICT organisation for Dutch education & research and coordinates the national e-infrastructure (surf.nl). To accelerate scientific discovery, SURF invests in, operates and explores high-end IT solutions for and wit…

LOFAR 144-MHz follow-up observations of GW170817 Open

J. W. Broderick, T. W. Shimwell, K. Gourdji, A. Rowlinson, S. Nissanke , et al. · 2020

We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO–Virgo. These data, with a central frequency of…

Building LOFAR as a Service Open

A. P. Mechev, J. B. R. Oonk, Aske Plaat, A. Danezi, T. W. Shimwell · 2019

The LOFAR radio telescope is a low-frequency aperture synthesis radio telescope with headquarters in the Netherlands and stations across Europe. As a general purpose telescope, LOFAR produces petabytes of data each year serving a wide rang…

Realising the LOFAR Two-Metre Sky Survey -- using the supercomputer JUWELS at the Forschungszentrum Jülich Open

A. Drabent, M. Hoeft, A. P. Mechev, J. B. R. Oonk, T. W. Shimwell , et al. · 2019

The new generation of high-resolution broad-band radio telescopes, like the Low Frequency Array (LOFAR), produces, depending on the level of compression, between 1 to 10 TB of data per hour after correlation. Such a large amount of scienti…

Searching for the largest bound atoms in space Open

K. L. Emig, P. Salas, F. de Gasperin, J. B. R. Oonk, M. C. Toribio , et al. · 2019

Context. Radio recombination lines (RRLs) at frequencies ν < 250 MHz trace the cold, diffuse phase of the interstellar medium, and yet, RRLs have been largely unexplored outside of our Galaxy. Next-generation low-frequency interferometers …

Constraining cold accretion on to supermassive black holes: molecular gas in the cores of eight brightest cluster galaxies revealed by joint CO and CN absorption Open

Tom Rose, A. C. Edge, F. Combes, M. Gaspari, S. Hamer , et al. · 2019

To advance our understanding of the fuelling and feedback processes which power the Universe’s most massive black holes, we require a significant increase in our knowledge of the molecular gas which exists in their immediate surroundings. …

Efficient Computation of Collisional ℓ-mixing Rate Coefficients in Astrophysical Plasmas Open

D. Vrinceanu, Roberto Onofrio, J. B. R. Oonk, P. Salas, H. R. Sadeghpour · 2019

We present analytical expressions for direct evaluation of ℓ -mixing rate coefficients in proton-excited hydrogen atom collisions and describe a software package for efficient numerical evaluation of the collisional rate coefficients. Comp…

Spectroscopy with the Engineering Development Array: cold H+ at 63 MHz towards the Galactic Centre Open

J. B. R. Oonk, E. Alexander, J. W. Broderick, M. Sokołowski, R. B. Wayth · 2019

The Engineering Development Array (EDA) is a single test station for Square Kilometre Array (SKA) precursor technology. We have used the EDA to detect low-frequency radio recombination lines (RRLs) from the Galactic Centre region. Low-freq…

Carbon radio recombination lines from gigahertz to megahertz frequencies towards Orion A Open

P. Salas, J. B. R. Oonk, K. L. Emig, C. H. M. Pabst, M. C. Toribio , et al. · 2019

Context. The combined use of carbon radio recombination lines (CRRLs) and the 158 μ m-[CII] line is a powerful tool for the study of the energetics and physical conditions (e.g., temperature and density) of photodissociation regions (PDRs)…

Deep and narrow CO absorption revealing molecular clouds in the Hydra-A brightest cluster galaxy Open

Tom Rose, A. C. Edge, F. Combes, M. Gaspari, S. Hamer , et al. · 2019

Active galactic nuclei play a crucial role in the accretion and ejection of gas in galaxies. Although their outflows are well studied, finding direct evidence of accretion has proved very difficult and has so far been done for very few sou…

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