Search Results - "Low-Frequency Array (LOFAR)"

Interstellar and intergalactic scattering as astrophysical probes by Koay, Jun Yi

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The effect of the ionosphere on astronomical observations below 100 MHz by De Gasperin, F., Mevius, M., Intema, Hubertus

“…We compare our predictions with data from the Low Frequency Array (LOFAR). We show that the systematic errors on the phases of the instrument can be described as a sum of four effects (clock, ionosphere 1st, 2nd, and 3rd order). …”
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Pipeline Collector: Gathering performance data for distributed astronomical pipelines by Mechev, A., Plaat, A., Oonk, J., Intema, Hubertus, Röttgering, H.

“…In this work we have developed such a utility and integrated it with the calibration pipeline of the Low Frequency Array, LOFAR, a leading radio telescope. We tested the tool by running the pipeline on several different compute platforms and collected the performance data. …”
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Using low-frequency pulsar observations to study the 3-D structure of the Galactic magnetic field by Sobey, Charlotte, LOFAR Collaborators, MWA Collaborators

“…This is demonstrated by a catalogue of RMs (corrected for ionospheric Faraday rotation) from the Low Frequency Array (LOFAR), with a growing complementary catalogue in the southern hemisphere from the Murchison Widefield Array (MWA). …”
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Gentle reenergization of electrons in merging galaxy clusters by De Gasperin, F., Intema, Hubertus, Shimwell, T., Brunetti, G., Brüggen, M., Enßlin, T., Van Weeren, R., Bonafede, A., Röttgering, H.

“…Although the hot thermal gas that pervades galaxy clusters is relatively well understood through observations with x-ray satellites, our understanding of the nonthermal part of the intracluster medium (ICM) remains incomplete. With Low-Frequency Array (LOFAR) and Giant Metrewave Radio Telescope (GMRT) observations, we have identified a phenomenon that can be unveiled only at extremely low radio frequencies and offers new insights into the nonthermal component. …”
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An Automated Scalable Framework for Distributing Radio Astronomy Processing Across Clusters and Clouds by Mechev, A., Oonk, J., Danezi, A., Shimwell, T., Schrijvers, C., Intema, Hubertus, Plaat, A., Rttgering, H.

“…The Low Frequency Array (LOFAR) radio telescope is an international aperture synthesis radio telescope used to study the Universe at low frequencies. …”
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The effect of the ionosphere on ultra-low-frequency radio-interferometric observations by De Gasperin, F., Mevius, M., Rafferty, D., Intema, Hubertus, Fallows, R.

“…We also provide guidelines for observations and data reduction at these frequencies with the LOw Frequency ARray (LOFAR) and future instruments such as the Square Kilometre Array (SKA). …”
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An Ultra-High Time Resolution Cosmic-Ray Detection Mode for the Murchison Widefield Array by Williamson, A., James, Clancy, Tingay, Steven, McSweeney, Sam, Ord, S.M.

“…The radio-wavelength detection of extensive air showers (EASs) initiated by cosmic-ray interactions in the Earth's atmosphere is a promising technique for investigating the origin of these particles and the physics of their interactions. The Low-frequency Array (LOFAR) and the Owens Valley Long Wavelength Array (OVRO-LWA) have both demonstrated that the dense cores of low-frequency radio telescope arrays yield detailed information on the radiation ground pattern, which can be used to reconstruct key EAS properties and infer the primary cosmic-ray composition. …”
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A plethora of diffuse steep spectrum radio sources in Abell 2034 revealed by LOFAR by Shimwell, T., Luckin, J., Brüggen, M., Brunetti, G., Intema, Hubertus, Owers, M., Röttgering, H., Stroe, A., Van Weeren, R., Williams, W., Cassano, R., De Gasperin, F., Hoang, D., Hardcastle, M., Sridhar, S., Sabater, J., Best, P., Bonafede, A., Chyzy, K., Enßlin, T., Ferrari, C., Haverkorn, M., Hoeft, M., Horellou, C., McKean, J., Morabito, L., Orrù, E., Pizzo, R., Retana-Montenegro, E., White, G.

“…With Low-Frequency Array (LOFAR) observations, we have discovered a diverse assembly of steep spectrum emission that is apparently associated with the intracluster medium (ICM) of the merging galaxy cluster Abell 2034. …”
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LOFAR discovery of an ultra-steep radio halo and giant head-tail radio galaxy in Abell 1132 by Wilber, A., Brüggen, M., Bonafede, A., Savini, F., Shimwell, T., van Weeren, R., Rafferty, D., Mechev, A., Intema, Hubertus, Andrade-Santos, F., Clarke, A., Mahony, E., Morganti, R., Prandoni, I., Brunetti, G., Röttgering, H., Mandal, S., de Gasperin, F., Hoeft, M.

“…Low-Frequency Array (LOFAR) observations at 144 MHz have revealed large-scale radio sources in the unrelaxed galaxy cluster Abell 1132. …”
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LOFAR 150-MHz observations of SS 433 and W50 by Broderick, J., Fender, R., Miller-Jones, James, Trushkin, S., Stewart, A., Anderson, Gemma, Staley, T., Blundell, K., Pietka, M., Markoff, S., Rowlinson, A., Swinbank, J., van der Horst, A., Bell, M., Breton, R., Carbone, D., Corbel, S., Eislöffel, J., Falcke, H., Grießmeier, J., Hessels, J., Kondratiev, V., Law, C., Molenaar, G., Serylak, M., Stappers, B., van Leeuwen, J., Wijers, R., Wijnands, R., Wise, M., Zarka, P.

“…We present Low-Frequency Array (LOFAR) high-band data over the frequency range 115-189 MHz for the X-ray binary SS 433, obtained in an observing campaign from 2013 February to 2014 May. …”
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Tracing low-mass galaxy clusters using radio relics: The discovery of Abell 3527-bis by De Gasperin, F., Intema, Hubertus, Ridl, J., Salvato, M., Van Weeren, R., Bonafede, A., Greiner, J., Cassano, R., Brüggen, M.

“…This technique might be used in future deep, low-frequency surveys such as those carried on by the Low Frequency Array (LOFAR), the Upgraded GMRT (uGMRT) and, ultimately, the Square Kilometre Array (SKA).…”
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LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31 by Heesen, V., Croston, J., Morganti, R., Hardcastle, M., Stewart, A., Best, P., Broderick, J., Brüggen, M., Brunetti, G., Chyzy, K., Harwood, J., Haverkorn, M., Hess, K., Intema, Hubertus, Jamrozy, M., Kunert-Bajraszewska, M., McKean, J., Orrú, E., Röttgering, H., Shimwell, T., Shulevski, A., White, G., Wilcots, E., Williams, W.

“…We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. …”
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Deep Very Large Array Observations of the Merging Cluster CIZA J2242.8+5301: Continuum and Spectral Imaging by Gennaro, G., Van Weeren, R., Hoeft, M., Kang, H., Ryu, D., Rudnick, L., Forman, W., Röttgering, H., Brüggen, M., Dawson, W., Golovich, N., Hoang, D., Intema, Hubertus, Jones, C., Kraft, R., Shimwell, T., Stroe, A.

“…Our Mach number estimates for the northern and southern relics, based on the radio spectral index map obtained using the VLA observations and existing LOw Frequency ARray (LOFAR) and Giant Metrewave Radio Telescope data, are consistent with previous radio and X-ray studies (MRN = 2.58 ± 0.17 and MRS = 2.10 ± 0.08). …”
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Systematic effects in LOFAR data: A unified calibration strategy by De Gasperin, F., Dijkema, T.J., Drabent, A., Mevius, M., Rafferty, D., Van Weeren, R., Brüggen, M., Callingham, J.R., Emig, K.L., Heald, G., Intema, Huib, Morabito, L.K., Offringa, A.R., Oonk, R., Orrù, E., Röttgering, H., Sabater, J., Shimwell, T., Shulevski, A., Williams, W.

“…The data taken with these interferometers, for example with the LOw Frequency ARray (LOFAR), are often calibrated in a low signal-to-noise ratio regime and the removal of critical systematic effects is challenging. …”
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Simulating the 21 cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs by Ciardi, B., Inoue, S., Abdalla, F.B., Asad, K., Bernardi, G., Bolton, James S., Brentjens, M., de Bruyn, A.G., Chapman, E., Daiboo, S., Fernandez, E.R., Ghosh, A., Graziani, L., Harker, G.J.A., Iliev, I.T., Jelic, V., Jensen, H., Kazemi, S., Koopmans, L.V.E., Martinez, O., Maselli, A., Mellema, G., Offringa, A.R., Pandey, V.N., Schaye, Joop, Thomas, R., Vedantham, H., Yatawatta, S., Zaroubi, S.

“…This is done employing simulations of cosmic reionization, together with estimates of the GRB radio afterglow flux and the instrumental characteristics of the LOw Frequency ARray (LOFAR). We find that absorption features could be marginally (with a S/N larger than a few) detected by LOFAR at z ≳ 7 if the GRB is a highly energetic event originating from Pop III stars, while the detection would be easier if the noise were reduced by one order of magnitude, i.e. similar to what is expected for the first phase of the Square Kilometre Array (SKA1-low). …”
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A LOFAR census of millisecond pulsars by Kondratiev, V., Verbiest, J., Hessels, J., Bilous, A., Stappers, B., Kramer, M., Keane, E., Noutsos, A., Oslowski, S., Breton, R., Hassall, T., Alexov, A., Cooper, S., Falcke, H., Grießmeier, J., Karastergiou, A., Kuniyoshi, M., Pilia, M., Sobey, Charlotte, Ter Veen, S., Van Leeuwen, J., Weltevrede, P., Bell, M., Broderick, J., Corbel, S., Eisloffel, J., Markoff, S., Rowlinson, A., Swinbank, J., Wijers, R., Wijnands, R., Zarka, P.

“…We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOw-Frequency ARray (LOFAR) in the frequency range 110-188 MHz. …”
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Corrigendum: A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations by Buitink, S., Corstanje, A., Falcke, H., Hörandel, J., Huege, T., Nelles, A., Rachen, J., Rossetto, L., Schellart, P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T., Anderson, J., Asgekar, A., Avruch, I., Bell, M., Bentum, M., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brouw, W., Brüggen, M., Butcher, H., Carbone, D., Ciardi, B., Conway, J., de Gasperin, F., de Geus, E., Deller, A., Dettmar, R., van Diepen, G., Duscha, S., Eislöffel, J., Engels, D., Enriquez, J., Fallows, R., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M., Grießmeier, J., Gunst, A., van Haarlem, M., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., Iacobelli, M., Intema, Hubertus, Juette, E., Karastergiou, A., Kondratiev, V., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J., Mevius, M., Mulcahy, D., Munk, H., Norden, M., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V., Pietka, M., Pizzo, R., Polatidis, A., Reich, W., Röttgering, H., Scaife, A., Schwarz, D., Serylak, M., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, M., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R., Wijers, R., Wijnholds, S., Wise, M., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, J.

“…Figure 1 of this Corrigendum shows measurements of the average value of Xmax for the Low Frequency Array (LOFAR), and earlier experiments using different techniques, now including the data from the Pierre Auger Observatory1, specifically the contribution of A. …”
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The LOFAR window on star-forming galaxies and AGNs – curved radio SEDs and IR–radio correlation at 0<z<2.5 by Calistro Rivera, G., Williams, W., Hardcastle, M., Duncan, K., Röttgering, H., Best, P., Brüggen, M., Chyzy, K., Conselice, C., de Gasperin, F., Engels, D., Gürkan, G., Intema, Hubertus, Jarvis, M., Mahony, E., Miley, G., Morabito, L., Prandoni, I., Sabater, J., Smith, D., Tasse, C., van der Werf, P., White, G.

“…The new spectral window probed by the Low Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of 1542 galaxies in ~7deg2 of the LOFAR Bootes field. …”
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Deep LOFAR observations of the merging galaxy cluster CIZA J2242.8+5301 by Hoang, D., Shimwell, T., Stroe, A., Akamatsu, H., Brunetti, G., Donnert, J., Intema, Hubertus, Mulcahy, D., Röttgering, H., van Weeren, R., Bonafede, A., Brüggen, M., Cassano, R., Chyzy, K., Enßlin, T., Ferrari, C., de Gasperin, F., Gu, L., Hoeft, M., Miley, G., Orrú, E., Pizzo, R., White, G.

“…In this paper, we present deep, high-fidelity, low-frequency images made with the LOw-Frequency Array (LOFAR) between 115.5 and 179 MHz. These images, with a noise of 140 µJy beam-1 and a resolution of ?…”
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