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1,086 results on '"Shimwell, T."'

251. Nearby galaxies in the LOFAR Two-metre Sky Survey

Author

Heesen, V., primary, Staffehl, M., additional, Basu, A., additional, Beck, R., additional, Stein, M., additional, Tabatabaei, F. S., additional, Hardcastle, M. J., additional, Chyży, K. T., additional, Shimwell, T. W., additional, Adebahr, B., additional, Beswick, R., additional, Bomans, D. J., additional, Botteon, A., additional, Brinks, E., additional, Brüggen, M., additional, Dettmar, R.-J., additional, Drabent, A., additional, de Gasperin, F., additional, Gürkan, G., additional, Heald, G. H., additional, Horellou, C., additional, Nikiel-Wroczynski, B., additional, Paladino, R., additional, Piotrowska, J., additional, Röttgering, H. J. A., additional, Smith, D. J. B., additional, and Tasse, C., additional

Published
2022
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252. Identifying active galactic nuclei via brightness temperature with sub-arcsecond international LOFAR telescope observations

Author

Morabito, Leah K, primary, Sweijen, F, additional, Radcliffe, J F, additional, Best, P N, additional, Kondapally, Rohit, additional, Bondi, Marco, additional, Bonato, Matteo, additional, Duncan, K J, additional, Prandoni, Isabella, additional, Shimwell, T W, additional, Williams, W L, additional, van Weeren, R J, additional, Conway, J E, additional, and Calistro Rivera, G, additional

Published
2022
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254. The redshift evolution of extragalactic magnetic fields

Author

Pomakov, V P, primary, O’Sullivan, S P, additional, Brüggen, M, additional, Vazza, F, additional, Carretti, E, additional, Heald, G H, additional, Horellou, C, additional, Shimwell, T, additional, Shulevski, A, additional, and Vernstrom, T, additional

Published
2022
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255. The Coma Cluster at LOFAR Frequencies. II. The Halo, Relic, and a New Accretion Relic

Author

Bonafede, A., primary, Brunetti, G., additional, Rudnick, L., additional, Vazza, F., additional, Bourdin, H., additional, Giovannini, G., additional, Shimwell, T. W., additional, Zhang, X., additional, Mazzotta, P., additional, Simionescu, A., additional, Biava, N., additional, Bonnassieux, E., additional, Brienza, M., additional, Brüggen, M., additional, Rajpurohit, K., additional, Riseley, C. J., additional, Stuardi, C., additional, Feretti, L., additional, Tasse, C., additional, Botteon, A., additional, Carretti, E., additional, Cassano, R., additional, Cuciti, V., additional, Gasperin, F. de, additional, Gastaldello, F., additional, Rossetti, M., additional, Rottgering, H. J. A., additional, Venturi, T., additional, and Weeren, R. J. van, additional

Published
2022
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256. CHANG-ES XXIII: Influence of a galactic wind in NGC 5775

Author

Heald, G.H., Heesen, V., Sridhar, S.S., Beck, R., Bomans, D.J., Brüggen, M., Chyży, K.T., Damas-Segovia, A., Dettmar, R.-J., English, J., Henriksen, R., Ideguchi, S., Irwin, J., Vortmeyer-Krause, M., Li, J.-T., Murphy, E.J., Nikiel-Wroczyński, B., Piotrowska, J., Rand, R.J., Shimwell, T., Stein, Y., Vargas, C.J., Wang, Q.D., Weeren, R.J. van, Wiegert, T., Heald, G.H., Heesen, V., Sridhar, S.S., Beck, R., Bomans, D.J., Brüggen, M., Chyży, K.T., Damas-Segovia, A., Dettmar, R.-J., English, J., Henriksen, R., Ideguchi, S., Irwin, J., Vortmeyer-Krause, M., Li, J.-T., Murphy, E.J., Nikiel-Wroczyński, B., Piotrowska, J., Rand, R.J., Shimwell, T., Stein, Y., Vargas, C.J., Wang, Q.D., Weeren, R.J. van, and Wiegert, T.

Abstract

Contains fulltext : 240247.pdf (Publisher’s version ) (Open Access)

Published
2022

257. Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project

Author

Sobey, C, Bassa, C.G., O’Sullivan, S.P., Callingham, J.R., Tan, C.M., Hessels, J.W.T., Kondratiev, V.I., Stappers, B.W., Tiburzi, C., Heald, G., Shimwell, T., Breton, R.P., Kirwan, M., Vedantham, H.K., Carretti, E., Grießmeier, J.-M., Haverkorn, M., Karastergiou, A., Sobey, C, Bassa, C.G., O’Sullivan, S.P., Callingham, J.R., Tan, C.M., Hessels, J.W.T., Kondratiev, V.I., Stappers, B.W., Tiburzi, C., Heald, G., Shimwell, T., Breton, R.P., Kirwan, M., Vedantham, H.K., Carretti, E., Grießmeier, J.-M., Haverkorn, M., and Karastergiou, A.

Abstract

Contains fulltext : 249740.pdf (Publisher’s version ) (Open Access)

Published
2022

258. Radio detection of chemically peculiar stars with LOFAR

Author

Hajduk, Ma., Leto, Paolo, Vedantham, H.K., Trigilio, Corrado, Haverkorn, Marijke, Shimwell, T., Callingham, J.R., White, G.J., Hajduk, Ma., Leto, Paolo, Vedantham, H.K., Trigilio, Corrado, Haverkorn, Marijke, Shimwell, T., Callingham, J.R., and White, G.J.

Abstract

Contains fulltext : 282478.pdf (Publisher’s version ) (Open Access)

Published
2022

259. Seeing the forest and the trees: A radio investigation of the ULIRG Mrk 273

Author

Ministerio de Ciencia e Innovación (España), European Research Council, European Commission, Kukreti, P., Morganti, R., Bondi, M., Oosterloo, T., Tadhunter, C., Morabito, L. K., Adams, E. A. K., Adebahr, B., de Blok, W. J. G., de Gasperin, F., Drabent, A., Hess, Kelley M., Ivashina, M. V., Kutkin, A., Mika, Á. M., Oostrum, L. C., Shimwell, T. W., van der Hulst, J. M., van Leeuwen, J., van Weeren, R. J., Vohl, D., Ziemke, J., Ministerio de Ciencia e Innovación (España), European Research Council, European Commission, Kukreti, P., Morganti, R., Bondi, M., Oosterloo, T., Tadhunter, C., Morabito, L. K., Adams, E. A. K., Adebahr, B., de Blok, W. J. G., de Gasperin, F., Drabent, A., Hess, Kelley M., Ivashina, M. V., Kutkin, A., Mika, Á. M., Oostrum, L. C., Shimwell, T. W., van der Hulst, J. M., van Leeuwen, J., van Weeren, R. J., Vohl, D., and Ziemke, J.

Abstract

Galaxy mergers have been observed to trigger nuclear activity by feeding gas to the central supermassive black hole. One such class of objects are Ultra Luminous InfraRed Galaxies (ULIRGs), which are mostly late stage major mergers of gas-rich galaxies. Recently, large-scale (∼100 kpc) radio continuum emission has been detected in a select number of ULIRGs, all of which also harbour powerful Active Galactic Nuclei (AGN). This hints at the presence of large-scale radio emission being evidence for nuclear activity. Exploring the origin of this radio emission and its link to nuclear activity requires high sensitivity multi-frequency data. We present such an analysis of the ULIRG Mrk 273. Using the International LOFAR telescope (ILT), we detected spectacular large-scale arcs in this system. This detection includes, for the first time, a giant ∼190 kpc arc in the north. We propose these arcs are fuelled by a low power radio AGN triggered by the merger. We also identified a bright ∼45 kpc radio ridge, which is likely related to the ionised gas nebula in that region. We combined this with high sensitivity data from APERture Tile In Focus (Apertif) and archival data from the Very Large Array (VLA) to explore the spectral properties. The ILT simultaneously allowed us to probe the nucleus at a resolution of ∼0.3″, where we detected three components, and, for the first time, diffuse emission around these components. Combining this with archival high frequency VLA images of the nucleus allowed us to detect absorption in one component, and a steep spectrum radio AGN in another. We then extrapolate from this case study to the importance of investigating the presence of radio emission in more ULIRGs and what it can tell us about the link between mergers and the presence of radio activity. © P. Kukreti et al. 2022.

Published
2022

260. Origin of the ring structures in Hercules A: Sub-arcsecond 144 MHz to 7 GHz observations

Author

European Commission, European Research Council, Ministerio de Ciencia e Innovación (España), Timmerman, R., van Weeren, R. J., Callingham, J. R., Cotton, W. D., Perley, R., Morabito, L. K., Gizani, N. A. B., Bridle, A. H., O'Dea, C.P., Baum, S. A., Tremblay, G. R., Kharb, P., Kassim, N. E., Röttgering, H. J. A., Botteon, A., Sweijen, F., Tasse, C., Brüggen, M., Moldón, Javier, Shimwell, T., Brunetti, G., European Commission, European Research Council, Ministerio de Ciencia e Innovación (España), Timmerman, R., van Weeren, R. J., Callingham, J. R., Cotton, W. D., Perley, R., Morabito, L. K., Gizani, N. A. B., Bridle, A. H., O'Dea, C.P., Baum, S. A., Tremblay, G. R., Kharb, P., Kassim, N. E., Röttgering, H. J. A., Botteon, A., Sweijen, F., Tasse, C., Brüggen, M., Moldón, Javier, Shimwell, T., and Brunetti, G.

Abstract

The prominent radio source Hercules A features complex structures in its radio lobes. Although it is one of the most comprehensively studied sources in the radio sky, the origin of the ring structures in the Hercules A radio lobes remains an open question. We present the first sub-arcsecond angular resolution images at low frequencies (<300 MHz) of Hercules A, made with the International LOFAR Telescope. With the addition of data from the Karl G. Jansky Very Large Array, we mapped the structure of the lobes from 144 MHz to 7 GHz. We explore the origin of the rings within the lobes of Hercules A, and test whether their properties are best described by a shock model, where shock waves are produced by the jet propagating in the radio lobe, or by an inner-lobe model, where the rings are formed by decelerated jetted plasma. From spectral index mapping our large frequency coverage reveals that the curvature of the different ring spectra increases with distance away from the central active galactic nucleus. We demonstrate that the spectral shape of the rings is consistent with synchrotron aging, which speaks in favor of an inner-lobe model where the rings are formed from the deposition of material from past periods of intermittent core activity. © R. Timmerman et al. 2022.

Published
2022

261. The galaxy group NGC 507: Newly detected AGN remnant plasma transported by sloshing

Author

Brienza, M., primary, Lovisari, L., additional, Rajpurohit, K., additional, Bonafede, A., additional, Gastaldello, F., additional, Murgia, M., additional, Vazza, F., additional, Bonnassieux, E., additional, Botteon, A., additional, Brunetti, G., additional, Drabent, A., additional, Hardcastle, M. J., additional, Pasini, T., additional, Riseley, C. J., additional, Röttgering, H. J. A., additional, Shimwell, T., additional, Simionescu, A., additional, and van Weeren, R. J., additional

Published
2022
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262. Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project

Author

Sobey, C., primary, Bassa, C. G., additional, O’Sullivan, S. P., additional, Callingham, J. R., additional, Tan, C. M., additional, Hessels, J. W. T., additional, Kondratiev, V. I., additional, Stappers, B. W., additional, Tiburzi, C., additional, Heald, G., additional, Shimwell, T., additional, Breton, R. P., additional, Kirwan, M., additional, Vedantham, H. K., additional, Carretti, E., additional, Grießmeier, J.-M., additional, Haverkorn, M., additional, and Karastergiou, A., additional

Published
2022
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263. The eROSITA Final Equatorial-Depth Survey (eFEDS)

Author

Pasini, T., primary, Brüggen, M., additional, Hoang, D. N., additional, Ghirardini, V., additional, Bulbul, E., additional, Klein, M., additional, Liu, A., additional, Shimwell, T. W., additional, Hardcastle, M. J., additional, Williams, W. L., additional, Botteon, A., additional, Gastaldello, F., additional, van Weeren, R. J., additional, Merloni, A., additional, de Gasperin, F., additional, Bahar, Y. E., additional, Pacaud, F., additional, and Ramos-Ceja, M., additional

Published
2022
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264. The Planck clusters in the LOFAR sky

Author

Botteon, A., primary, Shimwell, T. W., additional, Cassano, R., additional, Cuciti, V., additional, Zhang, X., additional, Bruno, L., additional, Camillini, L., additional, Natale, R., additional, Jones, A., additional, Gastaldello, F., additional, Simionescu, A., additional, Rossetti, M., additional, Akamatsu, H., additional, van Weeren, R. J., additional, Brunetti, G., additional, Brüggen, M., additional, Groeneveld, C., additional, Hoang, D. N., additional, Hardcastle, M. J., additional, Ignesti, A., additional, Di Gennaro, G., additional, Bonafede, A., additional, Drabent, A., additional, Röttgering, H. J. A., additional, Hoeft, M., additional, and de Gasperin, F., additional

Published
2022
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265. Sub-arcsecond imaging with the International LOFAR Telescope

Author

Morabito, L. K., Jackson, N. J., Mooney, S., Sweijen, F., Badole, S., Kukreti, P., Venkattu, D., Groeneveld, C., Kappes, A., Bonnassieux, E., Drabent, A., Iacobelli, M., Croston, J. H., Best, P. N., Bondi, M., Callingham, J. R., Conway, J. E., Deller, A. T., Hardcastle, M. J., McKean, J. P., Miley, G. K., Moldon, J., Röttgering, H. J. A., Tasse, C., Shimwell, T. W., van Weeren, R. J., Anderson, J. M., Asgekar, A., Avruch, I. M., van Bemmel, I. M., Bentum, M. J., Bonafede, A., Brouw, W. N., Butcher, H. R., Ciardi, B., Corstanje, A., Coolen, A., Damstra, S., de Gasperin, F., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Garrett, M. A., Griessmeier, J., Gunst, A. W., van Haarlem, M. P., Hoeft, M., van der Horst, A. J., Jütte, E., Kadler, M., Koopmans, L. V. E., Krankowski, A., Mann, G., Nelles, A., Oonk, J. B. R., Orru, E., Paas, H., Pandey, V. N., Pizzo, R. F., Pandey-Pommier, M., Reich, W., Rothkaehl, H., Ruiter, M., Schwarz, D. J., Shulevski, A., Soida, M., Tagger, M., Vocks, C., Wijers, R. A. M. J., Wijnholds, S. J., Wucknitz, O., Zarka, P., and Zucca, P.

Subjects
ddc:520
Abstract

Astronomy and astrophysics 658, A1 (2022). doi:10.1051/0004-6361/202140649, [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, although this is technically and logistically challenging. Here we present a calibration strategy that builds on previous high-resolution work with LOFAR. We give an overview of the calibration strategy and discuss the special challenges inherent to enacting high-resolution imaging with LOFAR, and describe the pipeline, which is publicly available, in detail. We demonstrate the calibration strategy by using the pipeline on P205+55, a typical LOFAR Two-metre Sky Survey (LoTSS) pointing. We perform in-field delay calibration, solution referencing to other calibrators, self-calibration, and imaging of example directions of interest in the field. For this specific field and these ionospheric conditions, dispersive delay solutions can be transferred between calibrators up to ~1.5 degrees away, while phase solution transferral works well over 1 degree. We demonstrate a check of the astrometry and flux density scale. Imaging in 17 directions, the restoring beam is typically 0.3' x 0.2' although this varies slightly over the entire 5 square degree field of view. We achieve ~80 to 300 $\mu$Jy/bm image rms noise, which is dependent on the distance from the phase centre; typical values are ~90 $\mu$Jy/bm for the 8 hour observation with 48 MHz of bandwidth. Seventy percent of processed sources are detected, and from this we estimate that we should be able to image ~900 sources per LoTSS pointing. This equates to ~3 million sources in the northern sky, which LoTSS will entirely cover in the next several years. Future optimisation of the calibration strategy for efficient post-processing of LoTSS at high resolution (LoTSS-HR) makes this estimate a lower limit., Published by EDP Sciences, Les Ulis

Published
2022
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266. A MeerKAT-meets-LOFAR study of MS 1455.0 + 2232: a 590 kiloparsec ‘mini’-halo in a sloshing cool-core cluster

Author

Riseley, C J, primary, Rajpurohit, K, additional, Loi, F, additional, Botteon, A, additional, Timmerman, R, additional, Biava, N, additional, Bonafede, A, additional, Bonnassieux, E, additional, Brunetti, G, additional, Enßlin, T, additional, Di Gennaro, G, additional, Ignesti, A, additional, Shimwell, T, additional, Stuardi, C, additional, Vernstrom, T, additional, and van Weeren, R J, additional

Published
2022
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267. Deep Low-frequency Radio Observations of A2256. I. The Filamentary Radio Relic

Author

Rajpurohit, K., primary, van Weeren, R. J., additional, Hoeft, M., additional, Vazza, F., additional, Brienza, M., additional, Forman, W., additional, Wittor, D., additional, Domínguez-Fernández, P., additional, Rajpurohit, S., additional, Riseley, C. J., additional, Botteon, A., additional, Osinga, E., additional, Brunetti, G., additional, Bonnassieux, E., additional, Bonafede, A., additional, Rajpurohit, A. S., additional, Stuardi, C., additional, Drabent, A., additional, Brüggen, M., additional, Dallacasa, D., additional, Shimwell, T. W., additional, Röttgering, H. J. A., additional, Gasperin, F. de, additional, Miley, G. K., additional, and Rossetti, M., additional

Published
2022
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268. A LOFAR view into the stormy environment of the galaxy cluster 2A0335+096

Author

Ignesti, A., primary, Brunetti, G., additional, Shimwell, T., additional, Gitti, M., additional, Birzan, L., additional, Botteon, A., additional, Brüggen, M., additional, de Gasperin, F., additional, Di Gennaro, G., additional, Edge, A. C., additional, Riseley, C. J., additional, Röttgering, H. J. A., additional, and van Weeren, R. J., additional

Published
2022
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269. The LOFAR Two-metre Sky Survey

Author

Shimwell, T. W., primary, Hardcastle, M. J., additional, Tasse, C., additional, Best, P. N., additional, Röttgering, H. J. A., additional, Williams, W. L., additional, Botteon, A., additional, Drabent, A., additional, Mechev, A., additional, Shulevski, A., additional, van Weeren, R. J., additional, Bester, L., additional, Brüggen, M., additional, Brunetti, G., additional, Callingham, J. R., additional, Chyży, K. T., additional, Conway, J. E., additional, Dijkema, T. J., additional, Duncan, K., additional, de Gasperin, F., additional, Hale, C. L., additional, Haverkorn, M., additional, Hugo, B., additional, Jackson, N., additional, Mevius, M., additional, Miley, G. K., additional, Morabito, L. K., additional, Morganti, R., additional, Offringa, A., additional, Oonk, J. B. R., additional, Rafferty, D., additional, Sabater, J., additional, Smith, D. J. B., additional, Schwarz, D. J., additional, Smirnov, O., additional, O’Sullivan, S. P., additional, Vedantham, H., additional, White, G. J., additional, Albert, J. G., additional, Alegre, L., additional, Asabere, B., additional, Bacon, D. J., additional, Bonafede, A., additional, Bonnassieux, E., additional, Brienza, M., additional, Bilicki, M., additional, Bonato, M., additional, Calistro Rivera, G., additional, Cassano, R., additional, Cochrane, R., additional, Croston, J. H., additional, Cuciti, V., additional, Dallacasa, D., additional, Danezi, A., additional, Dettmar, R. J., additional, Di Gennaro, G., additional, Edler, H. W., additional, Enßlin, T. A., additional, Emig, K. L., additional, Franzen, T. M. O., additional, García-Vergara, C., additional, Grange, Y. G., additional, Gürkan, G., additional, Hajduk, M., additional, Heald, G., additional, Heesen, V., additional, Hoang, D. N., additional, Hoeft, M., additional, Horellou, C., additional, Iacobelli, M., additional, Jamrozy, M., additional, Jelić, V., additional, Kondapally, R., additional, Kukreti, P., additional, Kunert-Bajraszewska, M., additional, Magliocchetti, M., additional, Mahatma, V., additional, Małek, K., additional, Mandal, S., additional, Massaro, F., additional, Meyer-Zhao, Z., additional, Mingo, B., additional, Mostert, R. I. J., additional, Nair, D. G., additional, Nakoneczny, S. J., additional, Nikiel-Wroczyński, B., additional, Orrú, E., additional, Pajdosz-Śmierciak, U., additional, Pasini, T., additional, Prandoni, I., additional, van Piggelen, H. E., additional, Rajpurohit, K., additional, Retana-Montenegro, E., additional, Riseley, C. J., additional, Rowlinson, A., additional, Saxena, A., additional, Schrijvers, C., additional, Sweijen, F., additional, Siewert, T. M., additional, Timmerman, R., additional, Vaccari, M., additional, Vink, J., additional, West, J. L., additional, Wołowska, A., additional, Zhang, X., additional, and Zheng, J., additional

Published
2022
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270. Accretion mode versus radio morphology in the LOFAR Deep Fields

Author

Mingo, B, primary, Croston, J H, additional, Best, P N, additional, Duncan, K J, additional, Hardcastle, M J, additional, Kondapally, R, additional, Prandoni, I, additional, Sabater, J, additional, Shimwell, T W, additional, Williams, W L, additional, Baldi, R D, additional, Bonato, M, additional, Bondi, M, additional, Dabhade, P, additional, Gürkan, G, additional, Ineson, J, additional, Magliocchetti, M, additional, Miley, G, additional, Pierce, J C S, additional, and Röttgering, H J A, additional

Published
2022
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271. Magnetic field strength in cosmic web filaments

Author

Carretti, Ettore, primary, Vacca, V, additional, O’Sullivan, S P, additional, Heald, G H, additional, Horellou, C, additional, Röttgering, H J A, additional, Scaife, A M M, additional, Shimwell, T W, additional, Shulevski, A, additional, Stuardi, C, additional, and Vernstrom, T, additional

Published
2022
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273. Deep sub-arcsecond wide-field imaging of the Lockman Hole field at 144 MHz

Author

Sweijen, F., primary, van Weeren, R. J., additional, Röttgering, H. J. A., additional, Morabito, L. K., additional, Jackson, N., additional, Offringa, A. R., additional, van der Tol, S., additional, Veenboer, B., additional, Oonk, J. B. R., additional, Best, P. N., additional, Bondi, M., additional, Shimwell, T. W., additional, Tasse, C., additional, and Thomson, A. P., additional

Published
2022
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274. Origin of the ring structures in Hercules A

Author

Timmerman, R., primary, van Weeren, R. J., additional, Callingham, J. R., additional, Cotton, W. D., additional, Perley, R., additional, Morabito, L. K., additional, Gizani, N. A. B., additional, Bridle, A. H., additional, O’Dea, C. P., additional, Baum, S. A., additional, Tremblay, G. R., additional, Kharb, P., additional, Kassim, N. E., additional, Röttgering, H. J. A., additional, Botteon, A., additional, Sweijen, F., additional, Tasse, C., additional, Brüggen, M., additional, Moldon, J., additional, Shimwell, T., additional, and Brunetti, G., additional

Published
2022
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275. Late-time Evolution and Modeling of the Off-axis Gamma-Ray Burst Candidate FIRST J141918.9+394036

Author

Mooley, K. P., primary, Margalit, B., additional, Law, C. J., additional, Perley, D. A., additional, Deller, A. T., additional, Lazio, T. J. W., additional, Bietenholz, M. F., additional, Shimwell, T., additional, Intema, H. T., additional, Gaensler, B. M., additional, Metzger, B. D., additional, Dong, D. Z., additional, Hallinan, G., additional, Ofek, E. O., additional, and Sironi, L., additional

Published
2022
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276. The Galactic Faraday rotation sky 2020

Author

Hutschenreuter, S., primary, Anderson, C. S., additional, Betti, S., additional, Bower, G. C., additional, Brown, J.-A., additional, Brüggen, M., additional, Carretti, E., additional, Clarke, T., additional, Clegg, A., additional, Costa, A., additional, Croft, S., additional, Van Eck, C., additional, Gaensler, B. M., additional, de Gasperin, F., additional, Haverkorn, M., additional, Heald, G., additional, Hull, C. L. H., additional, Inoue, M., additional, Johnston-Hollitt, M., additional, Kaczmarek, J., additional, Law, C., additional, Ma, Y. K., additional, MacMahon, D., additional, Mao, S. A., additional, Riseley, C., additional, Roy, S., additional, Shanahan, R., additional, Shimwell, T., additional, Stil, J., additional, Sobey, C., additional, O’Sullivan, S. P., additional, Tasse, C., additional, Vacca, V., additional, Vernstrom, T., additional, Williams, P. K. G., additional, Wright, M., additional, and Enßlin, T. A., additional

Published
2022
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277. The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2.

Author

O'Sullivan, S P, Shimwell, T W, Hardcastle, M J, Tasse, C, Heald, G, Carretti, E, Brüggen, M, Vacca, V, Sobey, C, Van Eck, C L, Horellou, C, Beck, R, Bilicki, M, Bourke, S, Botteon, A, Croston, J H, Drabent, A, Duncan, K, Heesen, V, and Ideguchi, S

Subjects
FARADAY effect, ASTRONOMICAL surveys, DATA release, COSMIC magnetic fields, LINEAR polarization
Abstract

A Faraday rotation measure (RM) catalogue, or RM Grid, is a valuable resource for the study of cosmic magnetism. Using the second data release (DR2) from the LOFAR Two-metre Sky Survey (LoTSS), we have produced a catalogue of 2461 extragalactic high-precision RM values across 5720 deg2 of sky (corresponding to a polarized source areal number density of ∼0.43 deg−2). The linear polarization and RM properties were derived using RM synthesis from the Stokes Q and U channel images at an angular resolution of 20 arcsec across a frequency range of 120 to 168 MHz with a channel bandwidth of 97.6 kHz. The fraction of total intensity sources (>1 mJy beam−1) found to be polarized was ∼0.2 per cent. The median detection threshold was 0.6 mJy beam−1 (8σ QU ), with a median RM uncertainty of 0.06 rad m−2 (although a systematic uncertainty of up to 0.3 rad m−2 is possible, after the ionosphere RM correction). The median degree of polarization of the detected sources is 1.8 per cent, with a range of 0.05 per cent to 31 per cent. Comparisons with cm-wavelength RMs indicate minimal amounts of Faraday complexity in the LoTSS detections, making them ideal sources for RM Grid studies. Host galaxy identifications were obtained for 88 per cent of the sources, along with redshifts for 79 per cent (both photometric and spectroscopic), with the median redshift being 0.6. The focus of the current catalogue was on reliability rather than completeness, and we expect future versions of the LoTSS RM Grid to have a higher areal number density. In addition, 25 pulsars were identified, mainly through their high degrees of linear polarization. [ABSTRACT FROM AUTHOR]

Published
2023
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278. A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70

Author

Hoang, D. N., primary, Zhang, X., additional, Stuardi, C., additional, Shimwell, T. W., additional, Bonafede, A., additional, Brüggen, M., additional, Brunetti, G., additional, Botteon, A., additional, Cassano, R., additional, de Gasperin, F., additional, Di Gennaro, G., additional, Hoeft, M., additional, Intema, H., additional, Rajpurohit, K., additional, Röttgering, H. J. A., additional, Simionescu, A., additional, and van Weeren, R. J., additional

Published
2021
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279. Low frequency radio properties of the z > ​5 quasar population

Author

Gloudemans, A. J., primary, Duncan, K. J., additional, Röttgering, H. J. A., additional, Shimwell, T. W., additional, Venemans, B. P., additional, Best, P. N., additional, Brüggen, M., additional, Calistro Rivera, G., additional, Drabent, A., additional, Hardcastle, M. J., additional, Miley, G. K., additional, Schwarz, D. J., additional, Saxena, A., additional, Smith, D. J. B., additional, and Williams, W. L., additional

Published
2021
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280. LoTSS jellyfish galaxies

Author

Roberts, I. D., primary, van Weeren, R. J., additional, McGee, S. L., additional, Botteon, A., additional, Drabent, A., additional, Ignesti, A., additional, Rottgering, H. J. A., additional, Shimwell, T. W., additional, and Tasse, C., additional

Published
2021
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281. The LOFAR LBA Sky Survey: Deep Fields

Author

Williams, W. L., primary, de Gasperin, F., additional, Hardcastle, M. J. H., additional, van Weeren, R., additional, Tasse, C., additional, Shimwell, T. W., additional, Best, P. N., additional, Bonato, M., additional, Bondi, M., additional, Brüggen, M., additional, Röttgering, H. J. A., additional, and Smith, D. J. B., additional

Published
2021
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282. A snapshot of the oldest active galactic nuclei feedback phases

Author

Brienza, M., primary, Shimwell, T. W., additional, de Gasperin, F., additional, Bikmaev, I., additional, Bonafede, A., additional, Botteon, A., additional, Brüggen, M., additional, Brunetti, G., additional, Burenin, R., additional, Capetti, A., additional, Churazov, E., additional, Hardcastle, M. J., additional, Khabibullin, I., additional, Lyskova, N., additional, Röttgering, H. J. A., additional, Sunyaev, R., additional, van Weeren, R. J., additional, Gastaldello, F., additional, Mandal, S., additional, Purser, S. J. D., additional, Simionescu, A., additional, and Tasse, C., additional

Published
2021
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283. The population of M dwarfs observed at low radio frequencies

Author

Callingham, J. R., primary, Vedantham, H. K., additional, Shimwell, T. W., additional, Pope, B. J. S., additional, Davis, I. E., additional, Best, P. N., additional, Hardcastle, M. J., additional, Röttgering, H. J. A., additional, Sabater, J., additional, Tasse, C., additional, van Weeren, R. J., additional, Williams, W. L., additional, Zarka, P., additional, de Gasperin, F., additional, and Drabent, A., additional

Published
2021
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284. CHANG-ES XXIII: influence of a galactic wind in NGC 5775

Author

Heald, G H, primary, Heesen, V, additional, Sridhar, S S, additional, Beck, R, additional, Bomans, D J, additional, Brüggen, M, additional, Chyży, K T, additional, Damas-Segovia, A, additional, Dettmar, R-J, additional, English, J, additional, Henriksen, R, additional, Ideguchi, S, additional, Irwin, J, additional, Krause, M, additional, Li, J-T, additional, Murphy, E J, additional, Nikiel-Wroczyński, B, additional, Piotrowska, J, additional, Rand, R J, additional, Shimwell, T, additional, Stein, Y, additional, Vargas, C J, additional, Wang, Q D, additional, van Weeren, R J, additional, and Wiegert, T, additional

Published
2021
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285. The ultra-steep diffuse radio emission observed in the cool-core cluster RX J1720.1+2638 with LOFAR at 54 MHz

Author

Biava, N, primary, de Gasperin, F, additional, Bonafede, A, additional, Edler, H W, additional, Giacintucci, S, additional, Mazzotta, P, additional, Brunetti, G, additional, Botteon, A, additional, Brüggen, M, additional, Cassano, R, additional, Drabent, A, additional, Edge, A C, additional, Enßlin, T, additional, Gastaldello, F, additional, Riseley, C J, additional, Rossetti, M, additional, Rottgering, H J A, additional, Shimwell, T W, additional, Tasse, C, additional, and van Weeren, R J, additional

Published
2021
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287. Abell 1430: A merging cluster with exceptional diffuse radio emission

Author

Hoeft, M., primary, Dumba, C., additional, Drabent, A., additional, Rajpurohit, K., additional, Rossetti, M., additional, Nuza, S. E., additional, van Weeren, R. J., additional, Meusinger, H., additional, Botteon, A., additional, Brunetti, G., additional, Shimwell, T. W., additional, Cassano, R., additional, Brüggen, M., additional, Röttgering, H. J. A., additional, Gastaldello, F., additional, Lovisari, L., additional, Yepes, G., additional, Andrade-Santos, F., additional, and Eckert, D., additional

Published
2021
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288. Discovery of a radio halo (and relic) in a $M_{500} < 2 \times 10^{14}$ M$_\odot$ cluster

Author

Botteon, A., Cassano, R., van Weeren, R. J., Shimwell, T. W., Bonafede, A., Brüggen, M., Brunetti, G., Cuciti, V., Dallacasa, D., de Gasperin, F., Di Gennaro, G., Gastaldello, F., Hoang, D. N., Rossetti, M., and Röttgering, H. J. A.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Radio halos are diffuse synchrotron sources observed in dynamically unrelaxed galaxy clusters. Current observations and models suggest that halos trace turbulent regions in the intra-cluster medium where mildly relativistic particles are re-accelerated during cluster mergers. Due to the higher luminosities and detection rates with increasing cluster mass, radio halos have been mainly observed in massive systems ($M_{500} \gtrsim 5 \times10^{14}$ M$_\odot$). Here, we report the discovery of a radio halo with a largest linear scale of $\simeq$750 kpc in PSZ2G145.92-12.53 ($z=0.03$) using LOFAR observations at 120$-$168 MHz. With a mass of $M_{500} = (1.9\pm0.2) \times 10^{14}$ M$_\odot$ and a radio power at 150 MHz of $P_{150} = (3.5 \pm 0.7) \times 10^{23}$ W/Hz, this is the least powerful radio halo in the least massive cluster discovered to date. Additionally, we discover a radio relic with a mildly convex morphology at $\sim$1.7 Mpc from the cluster center. Our results demonstrate that LOFAR has the potential to detect radio halos even in low-mass clusters, where the expectation to form them is very low ($\sim$5%) based on turbulent re-acceleration models. Together with the observation of large samples of clusters, this opens the possibility to constrain the low end of the power-mass relation of radio halos., Comment: 8 pages, 5 figures, 1 table (including appendix). Accepted for publication in ApJL

Published
2021

292. LOFAR observations of galaxy clusters in HETDEX

Author

van Weeren, R. J., primary, Shimwell, T. W., additional, Botteon, A., additional, Brunetti, G., additional, Brüggen, M., additional, Boxelaar, J. M., additional, Cassano, R., additional, Di Gennaro, G., additional, Andrade-Santos, F., additional, Bonnassieux, E., additional, Bonafede, A., additional, Cuciti, V., additional, Dallacasa, D., additional, de Gasperin, F., additional, Gastaldello, F., additional, Hardcastle, M. J., additional, Hoeft, M., additional, Kraft, R. P., additional, Mandal, S., additional, Rossetti, M., additional, Röttgering, H. J. A., additional, Tasse, C., additional, and Wilber, A. G., additional

Published
2021
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293. The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

Author

Sabater, J., Best, P. N., Tasse, C., Hardcastle, M. J., Shimwell, T. W., Nisbet, D., Jelić, Vibor, Callingham, J. R., Röttgering, H. J. A., Bonato, M., Bondi, M., Ciardi, B., Cochrane, R. K., Jarvis, M. J., Kondapally, R., Koopmans, L. V. E., O’Sullivan, S. P., Prandoni, I., Schwarz, D. J., Smith, D. J. B., Wang, L., Williams, W. L., and Zaroubi, S.

Subjects
surveys, catalogs, radio continuum: general, radio continuum: galaxies, Physics, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam−1 over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 h, it reaches a root mean square noise level of ≲20 μJy beam−1 in the central region (and below 30 μJy beam−1 over 10 square degrees). The resolution is ~6 arcsecs and 84 862 radio sources were detected in the full area (68 square degrees) with 74 127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per square degree in the central region (~5 square degrees). We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115-177 MHz ; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5 per cent. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level ; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10 per cent for ELAIS-N1.

Published
2021

294. Low frequency radio properties of the $z>5$ quasar population

Author

Gloudemans, A. J., Duncan, K. J., R��ttgering, H. J. A., Shimwell, T. W., Venemans, B. P., Best, P. N., Br��ggen, M., Rivera, G. Calistro, Drabent, A., Hardcastle, M. J., Miley, G. K., Schwarz, D. J., Saxena, A., Smith, D. J. B., and Williams, W. L.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Optically luminous quasars at $z > 5$ are important probes of super-massive black hole (SMBH) formation. With new and future radio facilities, the discovery of the brightest low-frequency radio sources in this epoch would be an important new probe of cosmic reionization through 21-cm absorption experiments. In this work, we systematically study the low-frequency radio properties of a sample of 115 known spectroscopically confirmed $z>5$ quasars using the second data release of the Low Frequency Array (LOFAR) Two Metre Sky survey (LoTSS-DR2), reaching noise levels of $\sim$80 $��$Jy beam$^{-1}$ (at 144 MHz) over an area of $\sim5720$ deg$^2$. We find that 41 sources (36%) are detected in LoTSS-DR2 at $>2 ��$ significance and we explore the evolution of their radio properties (power, spectral index, and radio loudness) as a function of redshift and rest-frame ultra-violet properties. We obtain a median spectral index of $-0.29^{+0.10}_{-0.09}$ by stacking 93 quasars using LoTSS-DR2 and Faint Images of the Radio Sky at Twenty Centimetres (FIRST) data at 1.4 GHz, in line with observations of quasars at $z, 11 pages, 10 figures, accepted for publication in A&A

Published
2021
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295. Large closed-field corona of WX UMa evidenced from radio observations

Author

Davis, I., Vedantham, H. K., Callingham, J. R., Shimwell, T. W., Vidotto, A. A., Zarka, P., Ray, T. P., and Drabent, A.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics::High Energy Astrophysical Phenomena, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

The space-weather conditions that result from stellar winds significantly impact the habitability of exoplanets. The conditions can be calculated from first principles if the necessary boundary conditions -- namely on the plasma density in the outer corona and the radial distance at which the plasma forces the closed magnetic field into an open geometry -- are specified. Low frequency radio observations ($\nu \lesssim 200$ MHz) of plasma and cyclotron emission from stars probe these magneto-ionic conditions. Here we report the detection of low-frequency ($120-167\,{\rm MHz}$) radio emission associated with the dMe6 star WX UMa. If the emission originates in WX UMa's corona, we show that the closed field regions extends to at least $\approx 10$ stellar radii, that is about a factor of a few larger than the solar value, and possibly to $\gtrsim 20$ stellar radii. Our results suggest that the magnetic-field structure of M dwarfs is in between Sun-like and planet-like configurations, where compact over-dense coronal loops with X-ray emitting plasma co-exist with a large-scale magnetosphere with lower plasma density and closed magnetic geometry., Comment: Accepted for publication in A&A, 10 pages, 7 figures, 2 tables

Published
2021
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296. A Snapshot Of The Oldest Active Galactic Nuclei Feedback Phases

Author

Brienza, M., Shimwell, T. W., de Gasperin, F., Bikmaev, I, Bonafede, A., Botteon, A., Brueggen, M., Brunetti, G., Burenin, R., Capetti, A., Churazov, E., Hardcastle, M. J., Khabibullin, I, Lyskova, N., Roettgering, H. J. A., Sunyaev, R., van Weeren, R. J., Gastaldello, F., Mandal, S., and Purser, S. J. D.

Abstract

Active galactic nuclei inject large amounts of energy into their host galaxies and surrounding environment, shaping their properties and evolution(1,2). In particular, active-galactic-nuclei jets inflate cosmic-ray lobes, which can rise buoyantly as light 'bubbles' in the surrounding medium(3), displacing and heating the encountered thermal gas and thus halting its spontaneous cooling. These bubbles have been identified in a wide range of systems(4,5). However, due to the short synchrotron lifetime of electrons, the most advanced phases of their evolution have remained observationally unconstrained, preventing us from fully understand their coupling with the external medium, and thus active galactic nuclei feedback. Simple subsonic hydrodynamic models(6,7) predict that the pressure gradients, naturally present around the buoyantly rising bubbles, transform them into toroidal structures, resembling mushroom clouds in a stratified atmosphere. The way and timescales on which these tori will eventually disrupt depend on various factors including magnetic fields and plasma viscosity(8,9). Here we report observations below 200 MHz, sensitive to the oldest radio-emitting particles, showing the late evolution of multiple generations of cosmic-ray active-galactic-nuclei bubbles in a galaxy group with unprecedented level of detail. The bubbles' buoyancy power can efficiently offset the radiative cooling of the intragroup medium. However, the bubbles still have not thoroughly mixed with the thermal gas, after hundreds of million years, probably under the action of magnetic fields.

Published
2021

297. III. Host-galaxy identifications and value added catalogues

Author

Kondapally, R., Best, P. N., Hardcastle, M. J., Nisbet, D., Bonato, M., Sabater, J., Duncan, K. J., McCheyne, I., Cochrane, R. K., Bowler, R. A. A., Williams, W. L., Shimwell, T. W., Tasse, C., Croston, J. H., Goyal, A., Jamrozy, M., Jarvis, M. J., Mahatma, V. H., Röttgering, H. J. A., Smith, D. J. B., Wołowska, A., Bondi, M., Brienza, M., Brown, M. J. I., Brüggen, M., Chambers, K., Garrett, M. A., Gürkan, G., Huber, M., Kunert-Bajraszewska, M., Magnier, E., Mingo, B., Mostert, R., Nikiel-Wroczyński, B., O’Sullivan, S. P., Paladino, R., Ploeckinger, T., Prandoni, I., Rosenthal, M. J., Schwarz, D. J., Shulevski, A., Wagenveld, J. D., and Wang, L.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the LOFAR Two Metre Sky Survey (LoTSS): the LoTSS Deep Fields. The first LoTSS Deep Fields data release consists of deep radio imaging at 150 MHz of the ELAIS-N1, Lockman Hole, and Boötes fields, down to RMS sensitives of around 20, 22, and 32 μJy beam−1, respectively. These fields are some of the best studied extra-galactic fields in the northern sky, with existing deep, wide-area panchromatic photometry from X-ray to infrared wavelengths, covering a total of ≈26 deg2. We first generated improved multi-wavelength catalogues in ELAIS-N1 and Lockman Hole; combined with the existing catalogue for Boötes, we present forced, matched aperture photometry for over 7.2 million sources across the three fields. We identified multi-wavelength counterparts to the radio detected sources, using a combination of the Likelihood Ratio method and visual classification, which greatly enhances the scientific potential of radio surveys and allows for the characterisation of the photometric redshifts and the physical properties of the host galaxies. The final radio-optical cross-matched catalogue consists of 81 951 radio-detected sources, with counterparts identified and multi-wavelength properties presented for 79 820 (>97%) sources. We also examine the properties of the host galaxies, and through stacking analysis find that the radio population with no identified counterpart is likely dominated by active galactic nuclei (AGN) at z ~ 3−4. This dataset contains one of the largest samples of radio-selected star-forming galaxies and AGN at these depths, making it ideal for studying the history of star-formation, and the evolution of galaxies and AGN across cosmic time.

Published
2021

298. The LOFAR LBA Sky Survey: Deep Fields I. The Bo��tes Field

Author

Williams, W. L., de Gasperin, F., Hardcastle, M. J. H., van Weeren, R., Tasse, C., Shimwell, T. W., Best, P. N., Bonato, M., Bondi, M., Br��ggen, M., R��ttgering, H. J. A., and Smith, D. J. B.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics
Abstract

We present the first sub-mJy ($\approx0.7$ mJy beam$^{-1}$) survey to be completed below 100 MHz, which is over an order of magnitude deeper than previously achieved for widefield imaging of any field at these low frequencies. The high resolution ($15 \times 15$ arcsec) image of the Bo��tes field at 34-75 MHz is made from 56 hours of observation with the LOw Frequency ARray (LOFAR) Low Band Antenna (LBA) system. The observations and data reduction, including direction-dependent calibration, are described here. We present a radio source catalogue containing 1,948 sources detected over an area of $23.6$ deg$^2$, with a peak flux density threshold of $5��$. Using existing datasets, we characterise the astrometric and flux density uncertainties, finding a positional uncertainty of $\sim1.2$ arcsec and a flux density scale uncertainty of about 5 per cent. Using the available deep 144-MHz data, we identified 144-MHz counterparts to all the 54-MHz sources, and produced a matched catalogue within the deep optical coverage area containing 829 sources. We calculate the Euclidean-normalised differential source counts and investigate the low-frequency radio source spectral indices between 54 and 144 MHz, both of which show a general flattening in the radio spectral indices for lower flux density sources, from $\sim-0.75$ at 144-MHz flux densities between 100-1000 mJy to $\sim-0.5$ at 144-MHz flux densities between 5-10 mJy, due to a growing population of star forming galaxies and compact core-dominated AGN., 15 pages, 17 figures. Accepted for publication by A&A. Data available online at lofar-surveys.org

Published
2021
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299. The population of M dwarfs observed at low radio frequencies

Author

Callingham, J. R., Vedantham, H. K., Shimwell, T. W., Pope, B. J. S., Davis, I. E., Best, P. N., Hardcastle, M. J., Röttgering, H. J. A., Sabater, J., Tasse, C., van Weeren, R. J., Williams, W. L., Zarka, P., de Gasperin, F., Drabent, A., Callingham, J. R., Vedantham, H. K., Shimwell, T. W., Pope, B. J. S., Davis, I. E., Best, P. N., Hardcastle, M. J., Röttgering, H. J. A., Sabater, J., Tasse, C., van Weeren, R. J., Williams, W. L., Zarka, P., de Gasperin, F., and Drabent, A.

Abstract

Coherent low-frequency (≲200 MHz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events and space weather. Previous low-frequency searches for radio-emitting stellar systems have lacked the sensitivity to detect the general population, instead largely focusing on targeted studies of anomalously active stars. Here we present 19 detections of coherent radio emission associated with known M dwarfs from a blind flux-limited low-frequency survey. Our detections show that coherent radio emission is ubiquitous across the M dwarf main sequence, and that the radio luminosity is independent of known coronal and chromospheric activity indicators. While plasma emission can generate the low-frequency emission from the most chromospherically active stars of our sample, the origin of the radio emission from the most quiescent sources is yet to be ascertained. Large-scale analogues of the magnetospheric processes seen in gas giant planets probably drive the radio emission associated with these quiescent stars. The slowest-rotating stars of this sample are candidate systems to search for star–planet interaction signatures.

Published
2021

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