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Pushing sub-arcsecond resolution imaging down to 30 MHz with the trans-European International LOFAR Telescope

Groeneveld, C.; van Weeren, R.J.; Miley, G.K.; Morabito, L.K.; de Gasperin, F.; Callingham, J.R.; Sweijen, F.; Brüggen, M.; Botteon, A.; Offringa, A.; Brunetti, G.; Moldon, J.; Bondi, M.; Kappes, A.; Röttgering, H.J.A.

Pushing sub-arcsecond resolution imaging down to 30 MHz with the trans-European International LOFAR Telescope Thumbnail


Authors

C. Groeneveld

R.J. van Weeren

G.K. Miley

F. de Gasperin

J.R. Callingham

F. Sweijen

M. Brüggen

A. Botteon

A. Offringa

G. Brunetti

J. Moldon

M. Bondi

A. Kappes

H.J.A. Röttgering



Abstract

Relatively little information is available about the Universe at ultra-low radio frequencies (ULF; i.e., below 50 MHz), although the ULF spectral window contains a wealth of unique diagnostics for studying galactic and extragalactic phenomena. Subarcsecond resolution imaging at these frequencies is extremely difficult, due to the long baselines (>1000 km) required and large ionospheric perturbations. We have conducted a pilot project to investigate the ULF performance and potential of the International LOFAR Telescope (ILT), a trans-European interferometric array with baselines up to ~2000 km and observing frequencies down to 10 MHz. We have successfully produced images with subarcsecond resolution for six radio sources at frequencies down to 30 MHz. This resolution is more than an order of magnitude better than pre-ILT observations at similar frequencies. The six targets that we imaged (3C 196, 3C 225, 3C 273, 3C 295, 3C 298, and 3C 380) are bright radio sources with compact structures. By comparing our data of 3C 196 and 3C 273 with observations at higher frequencies, we investigate their spatially resolved radio spectral properties. Our success shows that at frequencies down to 30 MHz, subarcsecond imaging with the ILT is possible. Further analysis is needed to determine the feasibility of observations of fainter sources or sources with less compact emission.

Citation

Groeneveld, C., van Weeren, R., Miley, G., Morabito, L., de Gasperin, F., Callingham, J., …Röttgering, H. (2022). Pushing sub-arcsecond resolution imaging down to 30 MHz with the trans-European International LOFAR Telescope. Astronomy & Astrophysics, 658, Article A9. https://doi.org/10.1051/0004-6361/202141352

Journal Article Type Article
Acceptance Date Sep 28, 2021
Online Publication Date Jan 25, 2022
Publication Date 2022-02
Deposit Date May 19, 2022
Publicly Available Date May 19, 2022
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 658
Article Number A9
DOI https://doi.org/10.1051/0004-6361/202141352

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Copyright Statement
C. Groeneveld et al, A&A, vol.658, A9, 2022, reproduced with permission, © ESO.







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