Browsing University of Hertfordshire by Author "Clarke, A. O."

Now showing items 1-11 of 11

    • The great Kite in the sky: a LOFAR observation of the radio source in Abell 2626 

      Ignesti, A.; Shimwell, T.; Brunetti, G.; Gitti, M.; Intema, H.; Weeren, R. J. van; Hardcastle, M. J.; Clarke, A. O.; Botteon, A.; Gennaro, G. Di; Brüggen, M.; Browne, I.; Mandal, S.; Röttgering, H. J. A.; Cuciti, V.; Gasperin, F. de; Cassano, R.; Scaife, Anna M.M. (2020-09-29)
      The radio source at the center of the galaxy cluster Abell 2626, also known as the Kite, stands out for its unique morphology composed of four, symmetric arcs. Previous studies have probed the properties of this source at ...

    • LOFAR MSSS: Detection of a low-frequency radio transient in 400 hrs of monitoring of the North Celestial Pole 

      Stewart, A. J.; Fender, R.P.; Broderick, J. W.; Hassall, T. E.; Muñoz-Darias, T.; Rowlinson, A.; Swinbank, J. D.; Staley, T. D.; Molenaar, G. J.; Scheers, B.; Grobler, T. L.; Pietka, M.; Heald, G.; McKean, J. P.; Bell, M. E.; Bonafede, A.; Breton, R. P.; Carbone, D.; Cendes, Y.; Clarke, A. O.; Corbel, S.; Gasperin, F. de; Eislöffel, J.; Falcke, H.; Ferrari, C.; Grießmeier, J. -M.; Hardcastle, M.J.; Heesen, V.; Hessels, J. W. T.; Horneffer, A.; Iacobelli, M.; Jonker, P.; Karastergiou, A.; Kokotanekov, G.; Kondratiev, V. I.; Kuniyoshi, M.; Law, C. J.; Leeuwen, J. van; Markoff, S.; Miller-Jones, J. C. A.; Mulcahy, D.; Orru, E.; Pandey-Pommier, M.; Pratley, L.; Rol, E.; Röttgering, H. J. A.; Scaife, A. M. M.; Shulevski, A.; Sobey, C. A.; Stappers, B. W.; Tasse, C.; van der Horst, A.J.; Velzen, S. van; Weeren, R. J. van; Wijers, R.A.M.J.; Wijnands, R.; Wise, M.; Zarka, P.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bernardi, G.; Best, P.; Breitling, F.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; Corstanje, A.; Geus, E. de; Deller, A.; Duscha, S.; Frieswijk, W.; Garrett, M.A.; Gunst, A. W.; Haarlem, M. P. van; Hoeft, M.; Hörandel, J.; Juette, E.; Kuper, G.; Loose, M.; Maat, P.; McFadden, R.; McKay-Bukowski, D.; Moldon, J.; Munk, H.; Norden, M. J.; Paas, H.; Polatidis, A. G.; Schwarz, D.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Wijnholds, S. J.; Wucknitz, O.; Yatawatta, S. (2016-03-01)
      We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The ...

    • LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group 

      Clarke, A. O.; Heald, G.; Jarrett, T.; Bray, J. D.; Hardcastle, Martin; Cantwell, T. M.; Scaife, A. M. M.; Brienza, M.; Bonafede, A.; Breton, R. P.; Broderick, J. W.; Carbone, D.; Croston, J. H.; Farnes, J. S.; Harwood, J. J.; Heesen, V.; Horneffer, A.; Horst, A. J. van der; Iacobelli, M.; Jurusik, W.; Kokotanekov, G.; McKean, J. P.; Morabito, L. K.; Mulcahy, D. D.; Nikiel-Wroczynski, B. S.; Orru, E.; Paladino, R.; Pandey-Pommier, M.; Pietka, M.; Pizzo, R.; Pratley, L.; Riseley, C. J.; Rottgering, H. J. A.; Rowlinson, A.; Sabater, J.; Sendlinger, K.; Shulevski, A.; Sridhar, S. S.; Stewart, A. J.; Tasse, C.; Velzen, S. van; Weeren, R. J. van; Wise, M. W. (2017-05-01)
      We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey (MSSS) of a giant radio galaxy (GRG) with a projected size of $2.56 \pm 0.07$ Mpc projected on the sky. It is associated with the galaxy triplet ...

    • LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies 

      Chyży, K. T.; Jurusik, W.; Piotrowska, J.; Nikiel-Wroczyński, B.; Heesen, V.; Vacca, V.; Nowak, N.; Paladino, R.; Surma, P.; Sridhar, S. S.; Heald, G.; Beck, R.; Conway, J.; Sendlinger, K.; Curyło, M.; Mulcahy, D.; Broderick, J. W.; Hardcastle, M. J.; Callingham, J. R.; Gürkan, G.; Iacobelli, M.; Röttgering, H. J. A.; Adebahr, B.; Shulevski, A.; Dettmar, R. -J.; Breton, R. P.; Clarke, A. O.; Farnes, J. S.; Orrú, E.; Pandey, V. N.; Pandey-Pommier, M.; Pizzo, R.; Riseley, C. J.; Rowlinson, A.; Scaife, A. M. M.; Stewart, A. J.; Horst, A. J. van der; Weeren, R. J. van (2018-11-07)
      Aims. The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take ...

    • LOFAR MSSS: The Scaling Relation between AGN Cavity Power and Radio Luminosity at Low Radio Frequencies 

      Kokotanekov, G.; Wise, Michael; Heald, G. H.; McKean, J. P.; Bîrzan, L.; Rafferty, D. A.; Godfrey, L. E H; Vries, M. de; Intema, Huib T.; Broderick, J. W.; Hardcastle, M. J.; Bonafede, A.; Clarke, A. O.; Weeren, R. J. van; Röttgering, H.~J.~A.; Pizzo, R.; Iacobelli, M.; Orrú, E.; Shulevski, Alexander; Riseley, C. J.; Breton, R. P.; Nikiel-Wroczyński, B.; Sridhar, S. S.; Stewart, A. J.; Rowlinson, A.; Horst, A. J. van der; Harwood, J. J.; Gürkan, G.; Carbone, D.; Pandey-Pommier, M.; Tasse, C.; Scaife, A. M. M.; Pratley, L.; Ferrari, Chiara; Croston, J. H.; Pandey, V. N.; Jurusik, W.; Mulcahy, D. D. (2017-09-07)
      We present a new analysis of the widely used relation between cavity power and radio luminosity in clusters of galaxies with evidence for strong AGN feedback. We study the correlation at low radio frequencies using two new ...

    • The LOFAR Multifrequency Snapshot Sky Survey (MSSS) : I. Survey description and first results 

      Heald, G. H.; Pizzo, R. F.; Orrú, E.; Breton, R. P.; Carbone, D.; Ferrari, C.; Hardcastle, M.J.; Jurusik, W.; Macario, G.; Mulcahy, D.; Rafferty, D.; Asgekar, A.; Brentjens, M.; Fallows, R. A.; Frieswijk, W.; Toribio, M. C.; Adebahr, B.; Arts, M.; Bell, M. R.; Bonafede, A.; Bray, J.; Broderick, J.; Cantwell, T.; Carroll, P.; Cendes, Y.; Clarke, A. O.; Croston, J. H.; Daiboo, S.; De Gasperin, F.; Gregson, J.; Harwood, J.; Hassall, T.; Heesen, V.; Horneffer, A.; van der Horst, A.J.; Iacobelli, M.; Jelić, V.; Jones, D.; Kant, D.; Kokotanekov, G.; Martin, P.; McKean, J. P.; Morabito, L. K.; Nikiel-Wroczyński, B.; Offringa, A.; Pandey, V. N.; Pandey-Pommier, M.; Pietka, M.; Pratley, L.; Riseley, C.; Rowlinson, A.; Sabater, J.; Scaife, A. M. M.; Scheers, L. H. A.; Sendlinger, K.; Shulevski, A.; Sipior, M.; Sobey, C.; Stewart, A. J.; Stroe, A.; Swinbank, J.; Tasse, C.; Trüstedt, J.; Varenius, E.; Van Velzen, S.; Vilchez, N.; Van Weeren, R. J.; Wijnholds, S.; Williams, W. L.; de Bruyn, A. G.; Nijboer, R.; Wise, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Van Bemmel, I.; Bentum, M. J.; Bernardi, G.; Best, P.; Breitling, F.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; De Geus, E.; De Jong, A.; De Vos, M.; Deller, A.; Dettmar, R. J.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fender, R.; Garrett, M.A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Holties, H. A.; Intema, H.; Jackson, N. J.; Jütte, E.; Karastergiou, A.; Klijn, W. F. A.; Kondratiev, V. I.; Koopmans, L. V. E.; Kuniyoshi, M.; Kuper, G.; Law, C.; Van Leeuwen, J.; Loose, M.; Maat, P.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; Mevius, M.; Miller-Jones, J. C A; Morganti, R.; Munk, H.; Nelles, A.; Noordam, J. E.; Norden, M. J.; Paas, H.; Polatidis, A. G.; Reich, W.; Renting, A.; Röttgering, H.; Schoenmakers, A.; Schwarz, D.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Steinmetz, M.; Tagger, M.; Tang, Y.; Ter Veen, S.; Thoudam, S.; Vermeulen, R.; Vocks, C.; Vogt, C.; Wijers, R.A.M.J.; Wucknitz, O.; Yatawatta, S.; Zarka, P. (2015-10-01)
      We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. ...

    • The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release 

      Shimwell, T. W.; Röttgering, H. J. A.; Best, P. N.; Williams, W. L.; Dijkema, T. J.; Gasperin, F. de; Hardcastle, M. J.; Heald, G. H.; Hoang, D. N.; Horneffer, A.; Intema, H.; Mahony, E. K.; Mandal, S.; Mechev, A. P.; Morabito, L.; Oonk, J. B. R.; Rafferty, D.; Retana-Montenegro, E.; Sabater, J.; Tasse, C.; Weeren, R. J. van; Brüggen, M.; Brunetti, G.; Chyży, K. T.; Conway, J. E.; Haverkorn, M.; Jackson, N.; Jarvis, M. J.; McKean, J. P.; Miley, G. K.; Morganti, R.; White, G. J.; Wise, M. W.; Bemmel, I. M. van; Beck, R.; Brienza, M.; Bonafede, A.; Rivera, G. Calistro; Cassano, R.; Clarke, A. O.; Cseh, D.; Deller, A.; Drabent, A.; Driel, W. van; Engels, D.; Falcke, H.; Ferrari, C.; Fröhlich, S.; Garrett, M. A.; Harwood, J. J.; Heesen, V.; Hoeft, M.; Horellou, C.; Israel, F. P.; Kapińska, A. D.; Kunert-Bajraszewska, M.; McKay, D. J.; Mohan, N. R.; Orrú, E.; Pizzo, R. F.; Prandoni, I.; Schwarz, D. J.; Shulevski, A.; Sipior, M.; Smith, D. J. B.; Sridhar, S. S.; Steinmetz, M.; Stroe, A.; Varenius, E.; Werf, P. P. van der; Zensus, J. A.; Zwart, J. T. L. (2017-02-09)
      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 hrs, which, at most declinations, is sufficient ...

    • Low-frequency observations of the Giant Radio Galaxy NGC 6251 

      Cantwell, T. M.; Bray, J. D.; Croston, J. H.; Scaife, A. M. M.; Mulcahy, D. D.; Best, P. N.; Bruggen, M.; Brunetti, G.; Callingham, J. R.; Clarke, A. O.; Hardcastle, M. J.; Harwood, J. J.; Heald, G.; Heesen, V.; Iacobelli, M.; Jamrozy, M.; Morganti, R.; Orru, E.; O'Sullivan, S. P.; Riseley, C. J.; Rottgering, H. J. A.; Shulevski, A.; Sridhar, S. S.; Tasse, C.; Eck, C. L. Van (2020-06-01)
      We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest-resolution images of NGC 6251 at these frequencies to date, revealing for ...

    • Signatures from a merging galaxy cluster and its AGN population : LOFAR observations of Abell 1682 

      Clarke, A. O.; Scaife, Anna M.M.; Shimwell, T.; Weeren, R. J. van; Bonafede, A.; Heald, George; Brunetti, G.; Cantwell, T. M.; Gasperin, F. de; Brüggen, M.; Botteon, A.; Hoeft, M.; Horellou, C.; Cassano, R.; Harwood, J. J.; Röttgering, H. J. A. (2019-07-05)
      We present LOFAR data from 110-180 MHz of the merging galaxy cluster Abell 1682, alongside archival optical, radio, and X-ray data. Our images of 6 arcsec in resolution at low frequencies reveal new structures associated ...

    • SKA Science Data Challenge 2: analysis and results 

      Hartley, P.; Bonaldi, A.; Braun, R.; Aditya, J. N. H. S.; Aicardi, S.; Alegre, L.; Chakraborty, A.; Chen, X.; Choudhuri, S.; Clarke, A. O.; Coles, J.; Collinson, J. S.; Cornu, D.; Darriba, L.; Veneri, M. Delli; Forbrich, J.; Fraga, B.; Galan, A.; Garrido, J.; Gubanov, F.; Håkansson, H.; Hardcastle, M. J.; Heneka, C.; Herranz, D.; Hess, K. M.; Jagannath, M.; Jaiswal, S.; Jurek, R. J.; Korber, D.; Kitaeff, S.; Kleiner, D.; Lao, B.; Lu, X.; Mazumder, A.; Moldón, J.; Mondal, R.; Ni, S.; Önnheim, M.; Parra, M.; Patra, N.; Peel, A.; Salomé, P.; Sánchez-Expósito, S.; Sargent, M.; Semelin, B.; Serra, P.; Shaw, A. K.; Shen, A. X.; Sjöberg, A.; Smith, L.; Soroka, A.; Stolyarov, V.; Tolley, E.; Toribio, M. C.; Hulst, J. M. van der; Sadr, A. Vafaei; Verdes-Montenegro, L.; Westmeier, T.; Yu, K.; Yu, L.; Zhang, L.; Zhang, X.; Zhang, Y.; Alberdi, A.; Ashdown, M.; Bom, C. R.; Brüggen, M.; Cannon, J.; Chen, R.; Combes, F.; Conway, J.; Courbin, F.; Ding, J.; Fourestey, G.; Freundlich, J.; Gao, L.; Gheller, C.; Guo, Q.; Gustavsson, E.; Jirstrand, M.; Jones, M. G.; Józsa, G.; Kamphuis, P.; Kneib, J. -P.; Lindqvist, M.; Liu, B.; Liu, Y.; Mao, Y.; Marchal, A.; Márquez, I.; Meshcheryakov, A.; Olberg, M.; Oozeer, N.; Pandey-Pommier, M.; Pei, W.; Peng, B.; Sabater, J.; Sorgho, A.; Starck, J. L.; Tasse, C.; Wang, A.; Wang, Y.; Xi, H.; Yang, X.; Zhang, H.; Zhang, J.; Zhao, M.; Zuo, S. (2023-08-31)
      The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order to conduct transformational science. SKAO data products made available to astronomers will be correspondingly large and complex, ...

    • Studying the late evolution of a radio-loud AGN in a galaxy group with LOFAR 

      Savini, F.; Bonafede, A.; Brüggen, M.; Wilber, A.; Harwood, J. J.; Murgia, M.; Shimwell, T.; Rafferty, D.; Shulevski, A.; Brienza, M.; Hardcastle, M. J.; Morganti, R.; Röttgering, H.; Clarke, A. O.; de Gasperin, F.; van Weeren, R.; Best, P. N.; Botteon, A.; Brunetti, G.; Cassano, R. (2018-03-11)
      Feedback by radio-loud active galactic nuclei (AGNs) in galaxy groups is not fully understood. Open questions include the duty cycle of theAGN, the spatial extent of the radio lobes, the effect they have on the intragroup ...