Euclid: Quick Data Release (Q1) -- Optical hotspots in powerful radio galaxies
Year: 2026
Type: article
Abstract: The hotspots of powerful radio galaxies are the sites of high-energy particle acceleration, but radio observations give us limited information on the electron energy distributions that they generate, which affects our overall understanding of their physics and energetics. Optical synchrotron counterparts to radio galaxy hotspots, which probe high electron energies, have been known for many years, but have only been studied in a small number of objects selected as being very bright in the radio. By combining Low-Frequency Array (LOFAR) observations with the Euclid Q1 data release in the Euclid Deep Field North, we identify 77 powerful radio galaxies with hotspots and show that a small but significant fraction of them, 7--15%, may have detected infrared and optical counterparts to their hotspots. The hotspot spectral energy distributions in our clearest cases are consistent with particle acceleration up to (but not beyond) 1,TeV in energy on the assumption of field strengths close to equipartition, whereas non-detected hotspots either do not reach such high electron energies or would have to have very different electron energy spectra or significantly sub-equipartition magnetic field strengths. Two new candidate optical hotspots are clearly detected matching high-resolution LOFAR data; one is remarkable as both the highest-redshift optical hotspot known to date (z ≈ 1.6) and also the first optical detection of the hotspot of the inner lobe of a restarting source. We discuss approaches to performing a large-scale study of hotspots with the full wide-area Euclid surveys, particularly when combined with the international baselines of LOFAR, enabling for the first time a statistical analysis of high-energy particle acceleration in hotspots.
Source: Astronomy and Astrophysics
Authors: M. J. Hardcastle, L. Bisigello, M. Bondi, M. Magliocchetti, L. K. Morabito, J. Petley, F. Ricci, H. J. A. Rottgering, K. Rubinur, D. J. B. Smith, D. Stern, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, M. Cropper, J.-G. Cuby, A. Da Silva, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Ferriol, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, J. Hoar, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, J. Skottfelt, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, O. R. Williams, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, J. García-Bellido, V. Scottez, F. Tarsitano, J. H. Knapen
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, UK Research and Innovation, Heising-Simons Foundation, European Space Agency, European Commission, University of Hertfordshire, Science Foundation Ireland, Bundesministerium für Bildung und Forschung, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Magyar Tudományos Akadémia, Agenzia Spaziale Italiana, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Université d'Orléans, National Astronomical Observatory of Japan, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Agenția Spațială Română, Ministerium für Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen, Norsk Romsenter, Office of Science, Observatoire de Paris, Université de Recherche Paris Sciences et Lettres, Science and Technology Facilities Council, Fundação para a Ciência e a Tecnologia, European Regional Development Fund, Agencia Estatal de Investigación, Lawrence Berkeley National Laboratory
Awards: G1039773812, G1079818582, G1143651532, G121809054, G1286236842, G1458934781, G1622782223, G1632040200, G1863003419, G2156317396, G2309174360, Hertfordshire Astronomy 2021-24, G2660406951, G3083819904, G3148402578, G3480869486, G3518538256, G3562095311, G4099714421, G419881185, G42916606, G4501827968, G4526231891, G4893482805, G498139845, G5080475149, G526230902, G5622099616, G6116975293, G639391236, G6447494072, Unveiling the physics of radio AGN feedback with LOFAR, LOFAR-UK 2016-2019: LOFAR-UK Compute Facility, G6652958823, G6876926712, Excellence in Galaxies - Twinning the IAC, G7084143925, Management and Operations of the National Optical Astronomy Observatory, G7354628648, LOFAR-UK Request for Continued Funding, 2021-2024, and LOFAR2.0 Upgrade, G7870178575, G8103039852, G8206910003, G8330169115, G8805661079, G8884978077, G8920660035, G897484643, G969889393
OpenAlex ID: W7213527216
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