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Now showing items 12975-12994 of 24103

    • The Lockman Hole project : LOFAR observations and spectral index properties of low-frequency radio sources 

      Mahony, E. K.; Morganti, R.; Prandoni, I.; Bemmel, I. M. van; Shimwell, T. W.; Brienza, M.; Best, P. N.; Brüggen, M.; Rivera, G. Calistro; Gasperin, F. de; Hardcastle, M. J.; Harwood, J. J.; Heald, G.; Jarvis, M. J.; Mandal, S.; Miley, G. K.; Retana-Montenegro, E.; Röttgering, H. J. A.; Sabater, J.; Tasse, C.; Velzen, S. van; Weeren, R. J. van; Williams, W. L.; White, G. J. (2016-12-11)
      The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterising the physical and evolutionary properties of the various source ...

    • LOFAR 144-MHz follow-up observations of GW170817 

      Broderick, J. W.; Shimwell, T. W.; Gourdji, K.; Rowlinson, A.; Nissanke, S.; Hotokezaka, K.; Jonker, P. G.; Tasse, C.; Hardcastle, M. J.; Oonk, J. B. R.; Fender, R. P.; Wijers, R. A. M. J.; Shulevski, A.; Stewart, A. J.; Veen, S. ter; Moss, V. A.; Wiel, M. H. D. van der; Nichols, D. A.; Piette, A.; Carbone, D.; Corbel, S.; Eislöffel, J.; Grießmeier, J. -M.; Keane, E. F.; Law, C. J.; Muñoz-Darias, T.; Pietka, M.; Serylak, M.; Horst, A. J. van der; Leeuwen, J. van; Wijnands, R.; Zarka, P.; Anderson, J. M.; Bentum, M. J.; Blaauw, R.; Brouw, W. N.; Brüggen, M.; Ciardi, B.; Vos, M. de; Duscha, S.; Fallows, R. A.; Franzen, T. M. O.; Garrett, M. A.; Gunst, A. W.; Hoeft, M.; Hörandel, J. R.; Iacobelli, M.; Jütte, E.; Koopmans, L. V. E.; Krankowski, A.; Maat, P.; Mann, G.; Mulder, H.; Nelles, A.; Paas, H.; Pandey-Pommier, M.; Pekal, R.; Reich, W.; Röttgering, H. J. A.; Schwarz, D. J.; Smirnov, O.; Soida, M.; Toribio, M. C.; Haarlem, M. P. van; Weeren, R. J. van; Vocks, C.; Wucknitz, O.; Zucca, P. (2020-06-01)
      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 ...

    • LOFAR 150-MHz observations of the Boötes field: Catalogue and Source Counts 

      Williams, W. L.; Van Weeren, R. J.; Röttgering, H. J. A.; Best, P.; Dijkema, T. J.; Gasperin, F. de; Hardcastle, M. J.; Heald, G.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Tasse, C.; Bemmel, I. M. van; Brüggen, M.; Brunetti, G.; Conway, J. E.; Enßlin, T.; Engels, D.; Falcke, H.; Ferrari, C.; Haverkorn, M.; Jackson, N.; Jarvis, M. J.; Kapinska, A. D.; Mahony, E. K.; Miley, G. K.; Morabito, L. K.; Morganti, R.; Orrú, E.; Retana-Montenegro, E.; Sridhar, S. S.; Toribio, M. C.; White, G. J.; Wise, M. W.; Zwart, J. T. L. (2016-08-11)
      We present the first wide area (19 deg$^2$), deep ($\approx120-150$ {\mu}Jy beam$^{-1}$), high resolution ($5.6 \times 7.4$ arcsec) LOFAR High Band Antenna image of the Bo\"otes field made at 130-169 MHz. This image is at ...

    • LOFAR and APERTIF Surveys of the Radio Sky : Probing Shocks and Magnetic Fields in Galaxy Clusters 

      Rottgering, Huub; Afonso, Jose; Barthel, Peter; Batejat, Fabien; Best, Philip; Bonafede, Annalisa; Brueggen, Marcus; Brunetti, Gianfranco; Chyzy, Krzysztof; Conway, John; De Gasperin, Francesco; Ferrari, Chiara; Haverkorn, Marijke; Heald, George; Hoeft, Matthias; Jackson, Neal; Jarvis, M.J.; Ker, Louise; Lehnert, Matt; Macario, Giulia; McKean, John; Miley, George; Morganti, Raffaella; Oosterloo, Tom; Orru, Emanuela; Pizzo, Roberto; Rafferty, David; Shulevski, Alexander; Tasse, Cyril; van Bemmel, Ilse; van der Tol, Bas; van Weeren, Reinout; Verheijen, Marc; White, Glenn; Wise, Michael (2011-12)
      At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF-phased arrays that are about ...

    • LOFAR Deep Fields : Probing a broader population of polarized radio galaxies in ELAIS-N1 

      Ruiz, N. Herrera; O'Sullivan, S. P.; Vacca, V.; Jelić, V.; Nikiel-Wroczyński, B.; Bourke, S.; Sabater, J.; Dettmar, R. -J.; Heald, G.; Horellou, C.; Piras, S.; Sobey, C.; Shimwell, T. W.; Tasse, C.; Hardcastle, M. J.; Kondapally, R.; Chyży, K. T.; Iacobelli, M.; Best, P. N.; Brüggen, M.; Carretti, E.; Prandoni, I. (2021-04-07)
      We present deep polarimetric observations of the European Large Area ISO Survey-North 1 (ELAIS-N1) field using the Low Frequency Array (LOFAR) at 114.9-177.4 MHz. The ELAIS-N1 field is part of the LOFAR Two-metre Sky Survey ...

    • LOFAR discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45 

      Cassano, R.; Botteon, A.; Gennaro, G. Di; Brunetti, G.; Sereno, M.; Shimwell, T. W.; Weeren, R. J. van; Brüggen, M.; Gastaldello, F.; Izzo, L.; Bîrzan, L.; Bonafede, A.; Cuciti, V.; Gasperin, F. de; Rötttgering, H. J. A.; Hardcastle, M.; Mechev, A. P.; Tasse, C. (2019-08-19)
      In this Letter, we report the discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45 ($z=0.616$) with the LOw Frequency ARray (LOFAR) at 120-168 MHz. This is one of the most distant radio halos ...

    • LOFAR early-time search for coherent radio emission from GRB 180706A 

      Rowlinson, A.; Gourdji, K.; Meulen, K. van der; Meyers, Z. S.; Shimwell, T. W.; Veen, S. ter; Wijers, R. A. M. J.; Kuiack, M. J.; Shulevski, A.; Broderick, J. W.; Horst, A. J. van der; Tasse, C.; Hardcastle, M. J.; Mechev, A. P.; Williams, W. L. (2019-10-21)
      The nature of the central engines of gamma-ray bursts (GRBs) and the composition of their relativistic jets are still under debate. If the jets are Poynting flux dominated rather than baryon dominated, a coherent radio ...

    • LOFAR facet calibration 

      Van Weeren, R. J.; Williams, W. L.; Hardcastle, M.J.; Shimwell, T. W.; Rafferty, D. A.; Sabater, J.; Heald, G.; Sridhar, S. S.; Dijkema, T. J.; Brunetti, G.; Brüggen, M.; Andrade-Santos, F.; Ogrean, G. A.; Röttgering, H. J. A.; Dawson, W. A.; Forman, W.R.; Gasperin, F. de; Jones, C.; Miley, G.K.; Rudnick, L.; Sarazin, C.L.; Bonafede, A.; Best, P. N.; Bîrzan, L.; Cassano, R.; Chyży, K. T.; Croston, J. H.; Ensslin, T.; Ferrari, C.; Hoeft, M.; Horellou, C.; Jarvis, M.J.; Kraft, R.P.; Mevius, M.; Intema, H. T.; Murray, S. S.; Orrú, E.; Pizzo, R.; Simionescu, A.; Stroe, A.; Tol, S. van der; White, G.J. (2016-03-07)
      LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides ...

    • LOFAR first look at the giant radio galaxy 3C 236 

      Shulevski, A.; Barthel, P. D.; Morganti, R.; Harwood, J. J.; Brienza, M.; Shimwell, T. W.; Röttgering, H. J. A.; White, G. J.; Callingham, J. R.; Mooney, S.; Rafferty, D. A. (2019-07-28)
      We have examined the giant radio galaxy 3C~236 using LOFAR at 143 MHz down to an angular resolution of 7", in combination with observations at higher frequencies. We have used the low frequency data to derive spectral index ...

    • LOFAR HBA observations of the Euclid Deep Field North (EDFN) 

      Bondi, M.; Scaramella, R.; Zamorani, G.; Ciliegi, P.; Vitello, F.; Arias, M.; Best, P.N.; Bonato, M.; Botteon, A.; Brienza, M.; Brunetti, G.; Hardcastle, M. J.; Magliocchetti, M.; Massaro, F.; Morabito, L. K; Pentericci, L.; Prandoni, I.; Röttgering, H. J. A.; Shimwell, T. W.; Tasse, C.; Weeren, R. J. van; White, G. J. (2024-03-18)
      We present the first deep (72 h of observations) radio image of the Euclid Deep Field North (EDFN) obtained with the LOw-Frequency ARray (LOFAR) High Band Antenna (HBA) at 144 MHz. The EDFN is the latest addition to the ...

    • LOFAR imaging of Cygnus A - direct detection of a turnover in the hotspot radio spectra 

      McKean, J. P.; Godfrey, L. E H; Vegetti, S.; Wise, Michael W.; Morganti, R.; Hardcastle, M. J.; Rafferty, D.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bemmel, I. M. van; Bentum, M. J.; Bernardi, G.; Best, Philip; Blaauw, R.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, Marcus; Cerrigone, L.; Ciardi, B.; De Gasperin, Francesco; Deller, A.; Duscha, S.; Engels, D.; Falcke, H.; Fallows, R. A.; Frieswijk, W.; Garrett, M.A.; Grießmeier, J. -M.; Haarlem, M. P. van; Heald, G.; Hoeft, Matthias; van der, HorstA J.; Iacobelli, M.; Interna, H.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Koopmans, L. V E; Kuniyoshi, M.; Kuper, G.; Van Leeuwen, J.; Maat, P.; Mann, R. G.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pietka, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rottgering, H. J. A.; Rowlinson, A.; Scaife, A. M M; Serylak, M.; Shulevski, Alexander; Sluman, J.; Smirnov, O.; Steinmetz, M.; Stewart, A. J.; Swinbank, J.; Tagger, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Van Weeren, R. J.; Wucknitz, O.; Yatawatta, S.; Zarka, P. (2016-12-01)
      The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for ...

    • The LOFAR LBA Sky Survey I. survey description and preliminary data release 

      Gasperin, F. de; Williams, W. L.; Best, P.; Bruggen, M.; Brunetti, G.; Cuciti, V.; Dijkema, T. J.; Hardcastle, M. J.; Norden, M. J.; Offringa, A.; Shimwell, T.; Weeren, R. van; Bomans, D.; Bonafede, A.; Botteon, A.; Callingham, J. R.; Cassano, R.; Chyzy, K. T.; Emig, K. L.; Edler, H.; Haverkorn, M.; Heald, G.; Heesen, V.; Iacobelli, M.; Intema, H. T.; Kadler, M.; Malek, K.; Mevius, M.; Miley, G.; Mingo, B.; Morabito, L. K.; Sabater, J.; Morganti, R.; Orru, E.; Pizzo, R.; Prandoni, I.; Shulevski, A.; Tasse, C.; Vaccari, M.; Zarka, P.; Rottgering, H. (2021-02-17)
      Context. The LOw Frequency ARray (LOFAR)istheonlyradiotelescopethatispresentlycapableofhigh-sensitivity,high-resolution (i.e. < 1mJybeam−1 and < 1500) observations at ultra-low frequencies(< 100MHz). To utilise these ...

    • The LOFAR LBA Sky Survey II. First data release 

      Gasperin, F. de; Edler, H. W.; Williams, W. L.; Callingham, J. R.; Asabere, B.; Bruggen, M.; Brunetti, G.; Dijkema, T. J.; Hardcastle, M. J.; Iacobelli, M.; Offringa, A.; Norden, M. J.; Rottgering, H. J. A.; Shimwell, T.; Weeren, R. J. van; Tasse, C.; Bomans, D. J.; Bonafede, A.; Botteon, A.; Cassano, R.; Chyzy, K. T.; Cuciti, V.; Emig, K. L.; Kadler, M.; Miley, G.; Mingo, B.; Oei, M. S. S. L.; Prandoni, I.; Schwarz, D. J.; Zarka, P. (2023-05-26)
      Context. The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15′′) and high sensitivity (<1 mJy beam−1 ). To exploit these ...

    • The LOFAR LBA Sky Survey: Deep Fields I. The Boötes Field 

      Williams, W. L.; Gasperin, F. de; Hardcastle, M. J. H.; Weeren, R. van; Tasse, C.; Shimwell, T. W.; Best, P. N.; Bonato, M.; Bondi, M.; Brüggen, M.; Röttgering, H. J. A.; Smith, D. J. B. (2021-11-10)
      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. ...

    • Lofar low-band antenna observations of the 3C 295 and boötes fields : Source counts and ultra-steep spectrum sources 

      Van Weeren, R. J.; Williams, W. L.; Tasse, C.; Röttgering, H. J.A.; Rafferty, D. A.; Van Der Tol, S.; Heald, G.; White, G. J.; Shulevski, A.; Best, P.; Intema, H. T.; Bhatnagar, S.; Reich, W.; Steinmetz, M.; Van Velzen, S.; Enßlin, T. A.; Prandoni, I.; De Gasperin, F.; Jamrozy, M.; Brunetti, G.; Jarvis, M. J.; McKean, J. P.; Wise, M. W.; Ferrari, C.; Harwood, J.; Oonk, J. B.R.; Hoeft, M.; Kunert-Bajraszewska, M.; Horellou, C.; Wucknitz, O.; Bonafede, A.; Mohan, N. R.; Scaife, A. M.M.; Klöckner, H. R.; Van Bemmel, I. M.; Merloni, A.; Chyzy, K. T.; Engels, D.; Falcke, H.; Pandey-Pommier, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Breitling, F.; Broderick, J.; De Vos, M. (2014-10-01)
      We present Low Frequency Array (LOFAR) Low Band observations of the Boötes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam-1, making them the deepest images ever obtained ...

    • A LOFAR mini-survey for low-frequency radio emission from the nearest brown dwarfs 

      Burningham, Ben; Hardcastle, Martin; Nichols, Jonathan; Casewell, Sarah; Littlefair, Stuart; Stark, Craig; Burleigh, Matthew; Metchev, Stanimir; Tannock, Megan; van Weeren, Reinout; Williams, Wendy Louise; Wynn, Graham (2016-12-01)
      We have conducted a mini-survey for low-frequency radio emission from some of the closest brown dwarfs to the Sun with rapid rotation rates: SIMP J013656.5+093347, WISEPC J150649.97+702736.0, and WISEPA J174124.26+255319.5. ...

    • 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 ...