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31 results on '"Klijn, W."'

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

Author

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., 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., and Zarka, P.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J2000 (RA,Dec)=(15h,69deg). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000-200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs., Comment: 23 pages, 19 figures. Accepted for publication in Astronomy & Astrophysics. MSSS Verification Field images and catalog data may be downloaded from http://vo.astron.nl

Published
2015
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2. Discovery of Carbon Radio Recombination Lines in absorption towards Cygnus~A

Author

Oonk, J. B. R., van Weeren, R. J., Salgado, F., Morabito, L. K., Tielens, A. G. G. M., Rottgering, H. J. A., Asgekar, A., White, G. J., Alexov, A., Anderson, J., Avruch, I. M., Batejat, F., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brueggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloeffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N. J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J. P., Mevius, M., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Scaife, A. M. M., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, A.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in the 33 to 57 MHz range. These low frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon $\alpha$ lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2$\times$10$^{-4}$, a line width of 10 km s$^{-1}$ and a velocity of +4 km s$^{-1}$ with respect to the local standard of rest. The associated gas is found to have an electron temperature $T_{e}\sim$ 110 K and density $n_{e}\sim$ 0.06 cm$^{-3}$. These properties imply that the observed carbon $\alpha$ absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3$\sigma$ peak optical depth limit of 1.5$\times$10$^{-4}$ for a 4 km s$^{-1}$ channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3$\sigma$ upper limit of 1.5$\times$10$^{-4}$ for the peak optical depth of these lines for a 4 km s$^{-1}$ channel width., Comment: In press

Published
2014
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3. Detecting cosmic rays with the LOFAR radio telescope

Author

Schellart, P., Nelles, A., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Frieswijk, W., Hörandel, J. R., Horneffer, A., James, C. W., Krause, M., Mevius, M., Scholten, O., ter Veen, S., Thoudam, S., Akker, M. van den, Alexov, A., Anderson, J., Avruch, I. M., Bähren, L., Beck, R., Bell, M. E., Bennema, P., Bentum, M. J., Bernardi, G., Best, P., Bregman, J., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Ciardi, B., Coolen, A., de Gasperin, F., de Geus, E., de Jong, A., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R. A., Ferrari, C., Garrett, M. A., Grießmeier, J., Grit, T., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Holties, H. A., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., McKean, J. P., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Nijboer, R., Norden, M. J., Orru, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A. G., Renting, A., Romein, J. W., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tang, Y., Tasse, C., Toribio, C., van Leeuwen, J., van Nieuwpoort, R., van Weeren, R. J., Vermaas, N., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wijnholds, S. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first $\sim 2\,\mathrm{years}$ of observing, 405 cosmic-ray events in the energy range of $10^{16} - 10^{18}\,\mathrm{eV}$ have been detected in the band from $30 - 80\,\mathrm{MHz}$. Each of these air showers is registered with up to $\sim1000$ independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.

Published
2013
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4. The brightness and spatial distributions of terrestrial radio sources

Author

Offringa, A. R., de Bruyn, A. G., Zaroubi, S., Koopmans, L. V. E., Wijnholds, S. J., Abdalla, F. B., Brouw, W. N., Ciardi, B., Iliev, I. T., Harker, G. J. A., Mellema, G., Bernardi, G., Zarka, P., Ghosh, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, I. M., Beck, R., Bell, M. E., Bell, M. R., Bentum, M. J., Best, P., Bîrzan, L., Breitling, F., Broderick, J., Brüggen, M., Butcher, H. R., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R. A., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Hassall, T. E., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, M., Maat, P., Macario, G., Mann, G., McKean, J. P., Meulman, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A. G., Rafferty, D., Reich, W., van Nieuwpoort, R., Röttgering, H., Scaife, A. M. M., Sluman, J., Smirnov, O., Sobey, C., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Toribio, C., Vermeulen, R., Vocks, C., van Weeren, R. J., Wise, M. W., and Wucknitz, O.

Subjects
Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Atmospheric and Oceanic Physics
Abstract

Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionisation (EoR) projects that try to detect the faint redshifted HI signals from the time of the earliest structures in the Universe. We explore the RFI situation at 30-163 MHz by studying brightness histograms of visibility data observed with LOFAR, similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around -1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR., Comment: Accepted for publication in MNRAS

Published
2013
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5. Tracking of an electron beam through the solar corona with LOFAR

Author

Mann, G., primary, Breitling, F., additional, Vocks, C., additional, Aurass, H., additional, Steinmetz, M., additional, Strassmeier, K. G., additional, Bisi, M. M., additional, Fallows, R. A., additional, Gallagher, P., additional, Kerdraon, A., additional, Mackinnon, A., additional, Magdalenic, J., additional, Rucker, H., additional, Anderson, J., additional, Asgekar, A., additional, Avruch, I. M., additional, Bell, M. E., additional, Bentum, M. J., additional, Bernardi, G., additional, Best, P., additional, Bîrzan, L., additional, Bonafede, A., additional, Broderick, J. W., additional, Brüggen, M., additional, Butcher, H. R., additional, Ciardi, B., additional, Corstanje, A., additional, de Gasperin, F., additional, de Geus, E., additional, Deller, A., additional, Duscha, S., additional, Eislöffel, J., additional, Engels, D., additional, Falcke, H., additional, Fender, R., additional, Ferrari, C., additional, Frieswijk, W., additional, Garrett, M. A., additional, Grießmeier, J., additional, Gunst, A. W., additional, van Haarlem, M., additional, Hassall, T. E., additional, Heald, G., additional, Hessels, J. W. T., additional, Hoeft, M., additional, Hörandel, J., additional, Horneffer, A., additional, Juette, E., additional, Karastergiou, A., additional, Klijn, W. F. A., additional, Kondratiev, V. I., additional, Kramer, M., additional, Kuniyoshi, M., additional, Kuper, G., additional, Maat, P., additional, Markoff, S., additional, McFadden, R., additional, McKay-Bukowski, D., additional, McKean, J. P., additional, Mulcahy, D. D., additional, Munk, H., additional, Nelles, A., additional, Norden, M. J., additional, Orru, E., additional, Paas, H., additional, Pandey-Pommier, M., additional, Pandey, V. N., additional, Pizzo, R., additional, Polatidis, A. G., additional, Rafferty, D., additional, Reich, W., additional, Röttgering, H., additional, Scaife, A. M. M., additional, Schwarz, D. J., additional, Serylak, M., additional, Sluman, J., additional, Smirnov, O., additional, Stappers, B. W., additional, Tagger, M., additional, Tang, Y., additional, Tasse, C., additional, ter Veen, S., additional, Thoudam, S., additional, Toribio, M. C., additional, Vermeulen, R., additional, van Weeren, R. J., additional, Wise, M. W., additional, Wucknitz, O., additional, Yatawatta, S., additional, Zarka, P., additional, and Zensus, J. A., additional

Published
2018
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7. The LOFAR Multifrequency Snapshot Sky Survey (MSSS)

Author

Heald, G., Pizzo, R., Orrú, E., Breton, R., Carbone, D., Ferrari, C., Hardcastle, M., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R., Frieswijk, W., Toribio, M., Adebahr, B., Arts, M., Bell, M., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A., Croston, J., Daiboo, S., de Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., van der Horst, A., Iacobelli, M., Jelić, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J., Morabito, L., Nikiel-Wroczyński, B., Offringa, A., Pandey, V., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A., Scheers, L., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, C., Stewart, A., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., van Velzen, S., Vilchez, N., van Weeren, R., Wijnholds, S., Williams, W., de Bruyn, A., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I., Beck, R., van Bemmel, I., Bentum, M., Bernardi, G., Best, P., Breitling, F., Brouw, W., Brüggen, M., Butcher, H., Ciardi, B., Conway, J., de Geus, E., de Jong, A., de Vos, M., Deller, A., Dettmar, R., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fender, R., Garrett, M., Grießmeier, J., Gunst, A., Hamaker, J., Hessels, J., Hoeft, M., Hörandel, J., Holties, H., Intema, H., Jackson, N., Jütte, E., Karastergiou, A., Klijn, W., Kondratiev, V., Koopmans, L., 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., Morganti, R., Munk, H., Nelles, A., Noordam, J., Norden, M., Paas, H., Polatidis, A., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R., Wucknitz, O., Yatawatta, S., and Zarka, P.

Abstract

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. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR’s multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the MSSS Verification Field (MVF), a region of 100 square degrees centered at (α,δ)J2000 = (15h,69°). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000–200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs.

Published
2015

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

Author

Heald, G., Pizzo, R., Orrú, E., Breton, R., Carbone, D., Ferrari, C., Hardcastle, M., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R., Frieswijk, W., Toribio, M., Adebahr, B., Arts, M., Bell, M., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A., Croston, J., Daiboo, S., de Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., van der Horst, A., Iacobelli, M., Jelic, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J., Morabito, L., Nikiel-Wroczynski, B., Offringa, A., Pandey, V., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A., Scheers, L., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, Charlotte Anne, Stewart, A., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., van Velzen, S., Vilchez, N., van Weeren, R., Wijnholds, S., Williams, W., De Bruyn, A., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I., Beck, R., van Bemmel, I., Bentum, M., Bernardi, G., Best, P., Breitling, F., Brouw, W., Brüggen, M., Butcher, H., Ciardi, B., Conway, J., de Geus, E., de Jong, A., de Vos, M., Deller, A., Dettmar, R., Duscha, S., Eislöffel, J., Engels, D., Falcke, J., Fender, R., Garrett, M., Grießmeier, J., Gunst, A., Hamaker, J., Hessels, J., Hoeft, J., Hörandel, J., Holties, H., Intema, H., Jackson, N., Jütte, E., Karastergiou, A., Klijn, W., Kondratiev, V., Koopmans, L., Kuniyoshi, M., Kuper, G., Law, C., van Leeuwen, J., Loose, M., Markoff, S., McFadden, R., McKay-Bukowski, D., Mevius, M., Miller-Jones, James, Morganti, R., Munk, H., Noordam, J., Norden, M., Pass, H., Polatidis, A., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R., Wucknitz, O., Yatawatta, S., Zarka, P., Nelles, A., Maat, P., Heald, G., Pizzo, R., Orrú, E., Breton, R., Carbone, D., Ferrari, C., Hardcastle, M., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R., Frieswijk, W., Toribio, M., Adebahr, B., Arts, M., Bell, M., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A., Croston, J., Daiboo, S., de Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., van der Horst, A., Iacobelli, M., Jelic, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J., Morabito, L., Nikiel-Wroczynski, B., Offringa, A., Pandey, V., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A., Scheers, L., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, Charlotte Anne, Stewart, A., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., van Velzen, S., Vilchez, N., van Weeren, R., Wijnholds, S., Williams, W., De Bruyn, A., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I., Beck, R., van Bemmel, I., Bentum, M., Bernardi, G., Best, P., Breitling, F., Brouw, W., Brüggen, M., Butcher, H., Ciardi, B., Conway, J., de Geus, E., de Jong, A., de Vos, M., Deller, A., Dettmar, R., Duscha, S., Eislöffel, J., Engels, D., Falcke, J., Fender, R., Garrett, M., Grießmeier, J., Gunst, A., Hamaker, J., Hessels, J., Hoeft, J., Hörandel, J., Holties, H., Intema, H., Jackson, N., Jütte, E., Karastergiou, A., Klijn, W., Kondratiev, V., Koopmans, L., Kuniyoshi, M., Kuper, G., Law, C., van Leeuwen, J., Loose, M., Markoff, S., McFadden, R., McKay-Bukowski, D., Mevius, M., Miller-Jones, James, Morganti, R., Munk, H., Noordam, J., Norden, M., Pass, H., Polatidis, A., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R., Wucknitz, O., Yatawatta, S., Zarka, P., Nelles, A., and Maat, P.

Abstract

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. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the MSSS Verification Field (MVF), a region of 100 square degrees centered at (a,d)J2000 = (15h,69°). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108? resolution, and 550 mJy at 50 MHz with 166? resolution. Images and catalogs for the full survey, expected to contain 150 000-200 000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs.

Published
2015

9. The LOFAR Multifrequency Snapshot Sky Survey (MSSS)

Author

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

Published
2015
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10. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author

Oonk, J. B. R., van Weeren, R. J., Salgado, F., Morabito, L. K., Tielens, A. G. G. M., Rottgering, H. J. A., Asgekar, A., White, G. J., Alexov, A., Anderson, J., Avruch, I. M., Batejat, F., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N. J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J. P., Mevius, M., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Scaife, A. M. M., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Veen, S. t., Thoudam, Satyendra, Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Oonk, J. B. R., van Weeren, R. J., Salgado, F., Morabito, L. K., Tielens, A. G. G. M., Rottgering, H. J. A., Asgekar, A., White, G. J., Alexov, A., Anderson, J., Avruch, I. M., Batejat, F., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N. J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J. P., Mevius, M., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Scaife, A. M. M., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Veen, S. t., Thoudam, Satyendra, Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, A.

Abstract

We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the Low Frequency Array in the 33–57 MHz range. These low-frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon α lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2 × 10−4, a line width of 10 km s−1 and a velocity of +4 km s−1 with respect to the local standard of rest. The associated gas is found to have an electron temperature Te ∼ 110 K and density ne ∼ 0.06 cm−3. These properties imply that the observed carbon α absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3σ peak optical depth limit of 1.5 × 10−4 for a 4 km s−1 channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3σ upper limit of 1.5 × 10−4 for the peak optical depth of these lines for a 4 km s−1 channel width.

Published
2014
Full Text
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11. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author

Oonk, J., van Weeren, R., Salgado, F., Morabito, L., Tielens, A., Rottgering, H., Asgekar, A., White, G., Alexov, A., Anderson, J., Avruch, I., Batejat, F., Beck, R., Bell, M., van Bemmel, I., Bentum, M., BERNARDI, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Butcher, H., Ciardi, B., Conway, J., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M., Grießmeier, J., Hamaker, J., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J., Mevius, M., Miller-Jones, James, Mol, J., Mulcahy, D., Munk, H., Norden, M., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V., Pizzo, R., Polatidis, A., Reich, W., Scaife, A., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R., Wise, M., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, J., Oonk, J., van Weeren, R., Salgado, F., Morabito, L., Tielens, A., Rottgering, H., Asgekar, A., White, G., Alexov, A., Anderson, J., Avruch, I., Batejat, F., Beck, R., Bell, M., van Bemmel, I., Bentum, M., BERNARDI, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Butcher, H., Ciardi, B., Conway, J., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M., Grießmeier, J., Hamaker, J., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J., Mevius, M., Miller-Jones, James, Mol, J., Mulcahy, D., Munk, H., Norden, M., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V., Pizzo, R., Polatidis, A., Reich, W., Scaife, A., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R., Wise, M., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, J.

Abstract

We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the Low Frequency Array in the 33–57MHz range. These low-frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon a lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2 × 10-4, a line width of 10 km s-1 and a velocity of +4 kms-1 with respect to the local standard of rest. The associated gas is found to have an electron temperature Te ~ 110K and density ne ~ 0.06 cm-3. These properties imply that the observed carbon a absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3s peak optical depth limit of 1.5 × 10-4 for a 4 kms-1 channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3s upper limit of 1.5 × 10-4 for the peak optical depth of these lines for a 4 kms-1 channel width.

Published
2014

12. The brightness and spatial distributions of terrestrial radio sources

Author

Offringa, Andre, Butcher, Harvey, de Bruyn, A. G., Zaroubi, Saleem, Koopmans, L. V. E., Wijnholds, S. J., Abdalla, Filipe B., Brouw, W. N., Ciardi, Benedetta, Iliev, I. T., Harker, Geraint, Mellema, G., Bernardi, G., Zarka, P., Ghosh, A., Alexov, A., Anderson, J. M., Asgekar, A., Avruch, Ian M., Bell, Michael R., Bentum, M. J., Breitling, F., de Gasperin, F., de Geus, Eugene, de Vos, Marco, Duscha, S., Fallows, R. A., Frieswijk, W., Garrett, M. A., Iacobelli, M., Klijn, W., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Mann, Gottfried, McKean, J. P., Norden, M. J., Pizzo, R., Polatidis, A. G., Rafferty, D. A., Reich, W., Van Nieuwpoort, Rob, Sluman, J., Sobey, C., Tang, Y., Toribio, C., Vermeulen, R. C., Vocks, Christian, Wise, M. J., Offringa, Andre, Butcher, Harvey, de Bruyn, A. G., Zaroubi, Saleem, Koopmans, L. V. E., Wijnholds, S. J., Abdalla, Filipe B., Brouw, W. N., Ciardi, Benedetta, Iliev, I. T., Harker, Geraint, Mellema, G., Bernardi, G., Zarka, P., Ghosh, A., Alexov, A., Anderson, J. M., Asgekar, A., Avruch, Ian M., Bell, Michael R., Bentum, M. J., Breitling, F., de Gasperin, F., de Geus, Eugene, de Vos, Marco, Duscha, S., Fallows, R. A., Frieswijk, W., Garrett, M. A., Iacobelli, M., Klijn, W., Kondratiev, V. I., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Mann, Gottfried, McKean, J. P., Norden, M. J., Pizzo, R., Polatidis, A. G., Rafferty, D. A., Reich, W., Van Nieuwpoort, Rob, Sluman, J., Sobey, C., Tang, Y., Toribio, C., Vermeulen, R. C., Vocks, Christian, and Wise, M. J.

Abstract

Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issu

Published
2013

13. The brightness and spatial distributions of terrestrial radio sources

Author

Offringa, A., De Bruyn, A., Zaroubi, S., Koopmans, L., Wijnholds, S., Abdalla, F., Brouw, W., Ciardi, B., Iliev, I., Harker, G., Mellema, G., Bernardi, G., Zarka, P., Ghosh, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, I., Beck, R., Bell, M., Bentum, M., Best, P., Bîrzan, L., Breitling, F., Broderick, J., Brüggen, M., Butcher, H., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R., Ferrari, C., Frieswijk, W., Garrett, M., Grießmeier, J., Hassall, T., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kondratiev, V., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, M., Maat, P., Macario, G., Mann, G., McKean, J., Meulman, H., Norden, M., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A., Rafferty, D., Reich, W., van Nieuwpoort, R., Röttgering, H., Scaife, A., Sluman, J., Smirnov, O., Sobey, Charlotte, Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Toribio, C., Vermeulen, R., Vocks, C., van Weeren, R., Wise, M., Wucknitz, O., Offringa, A., De Bruyn, A., Zaroubi, S., Koopmans, L., Wijnholds, S., Abdalla, F., Brouw, W., Ciardi, B., Iliev, I., Harker, G., Mellema, G., Bernardi, G., Zarka, P., Ghosh, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, I., Beck, R., Bell, M., Bentum, M., Best, P., Bîrzan, L., Breitling, F., Broderick, J., Brüggen, M., Butcher, H., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R., Ferrari, C., Frieswijk, W., Garrett, M., Grießmeier, J., Hassall, T., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kondratiev, V., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, M., Maat, P., Macario, G., Mann, G., McKean, J., Meulman, H., Norden, M., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A., Rafferty, D., Reich, W., van Nieuwpoort, R., Röttgering, H., Scaife, A., Sluman, J., Smirnov, O., Sobey, Charlotte, Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Toribio, C., Vermeulen, R., Vocks, C., van Weeren, R., Wise, M., and Wucknitz, O.

Abstract

Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionization (EoR) projects that try to detect the faint redshifted H I signals from the time of the earliest structures in the Universe.We explore the RFI situation at 30-163MHz by studying brightness histograms of visibility data observed with Low-Frequency Array (LOFAR), similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around -1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Published
2013

14. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author

Oonk, J. B. R., primary, van Weeren, R. J., additional, Salgado, F., additional, Morabito, L. K., additional, Tielens, A. G. G. M., additional, Rottgering, H. J. A., additional, Asgekar, A., additional, White, G. J., additional, Alexov, A., additional, Anderson, J., additional, Avruch, I. M., additional, Batejat, F., additional, Beck, R., additional, Bell, M. E., additional, van Bemmel, I., additional, Bentum, M. J., additional, Bernardi, G., additional, Best, P., additional, Bonafede, A., additional, Breitling, F., additional, Brentjens, M., additional, Broderick, J., additional, Brüggen, M., additional, Butcher, H. R., additional, Ciardi, B., additional, Conway, J. E., additional, Corstanje, A., additional, de Gasperin, F., additional, de Geus, E., additional, de Vos, M., additional, Duscha, S., additional, Eislöffel, J., additional, Engels, D., additional, van Enst, J., additional, Falcke, H., additional, Fallows, R. A., additional, Fender, R., additional, Ferrari, C., additional, Frieswijk, W., additional, Garrett, M. A., additional, Grießmeier, J., additional, Hamaker, J. P., additional, Hassall, T. E., additional, Heald, G., additional, Hessels, J. W. T., additional, Hoeft, M., additional, Horneffer, A., additional, Horst, A. van der, additional, Iacobelli, M., additional, Jackson, N. J., additional, Juette, E., additional, Karastergiou, A., additional, Klijn, W., additional, Kohler, J., additional, Kondratiev, V. I., additional, Kramer, M., additional, Kuniyoshi, M., additional, Kuper, G., additional, van Leeuwen, J., additional, Maat, P., additional, Macario, G., additional, Mann, G., additional, Markoff, S., additional, McKean, J. P., additional, Mevius, M., additional, Miller-Jones, J. C. A., additional, Mol, J. D., additional, Mulcahy, D. D., additional, Munk, H., additional, Norden, M. J., additional, Orru, E., additional, Paas, H., additional, Pandey-Pommier, M., additional, Pandey, V. N., additional, Pizzo, R., additional, Polatidis, A. G., additional, Reich, W., additional, Scaife, A. M. M., additional, Schoenmakers, A., additional, Schwarz, D., additional, Shulevski, A., additional, Sluman, J., additional, Smirnov, O., additional, Sobey, C., additional, Stappers, B. W., additional, Steinmetz, M., additional, Swinbank, J., additional, Tagger, M., additional, Tang, Y., additional, Tasse, C., additional, Veen, S. ter, additional, Thoudam, S., additional, Toribio, C., additional, van Nieuwpoort, R., additional, Vermeulen, R., additional, Vocks, C., additional, Vogt, C., additional, Wijers, R. A. M. J., additional, Wise, M. W., additional, Wucknitz, O., additional, Yatawatta, S., additional, Zarka, P., additional, and Zensus, A., additional

Published
2013
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15. Detecting cosmic rays with the LOFAR radio telescope

Author

Schellart, P., primary, Nelles, A., additional, Buitink, S., additional, Corstanje, A., additional, Enriquez, J. E., additional, Falcke, H., additional, Frieswijk, W., additional, Hörandel, J. R., additional, Horneffer, A., additional, James, C. W., additional, Krause, M., additional, Mevius, M., additional, Scholten, O., additional, ter Veen, S., additional, Thoudam, S., additional, van den Akker, M., additional, Alexov, A., additional, Anderson, J., additional, Avruch, I. M., additional, Bähren, L., additional, Beck, R., additional, Bell, M. E., additional, Bennema, P., additional, Bentum, M. J., additional, Bernardi, G., additional, Best, P., additional, Bregman, J., additional, Breitling, F., additional, Brentjens, M., additional, Broderick, J., additional, Brüggen, M., additional, Ciardi, B., additional, Coolen, A., additional, de Gasperin, F., additional, de Geus, E., additional, de Jong, A., additional, de Vos, M., additional, Duscha, S., additional, Eislöffel, J., additional, Fallows, R. A., additional, Ferrari, C., additional, Garrett, M. A., additional, Grießmeier, J., additional, Grit, T., additional, Hamaker, J. P., additional, Hassall, T. E., additional, Heald, G., additional, Hessels, J. W. T., additional, Hoeft, M., additional, Holties, H. A., additional, Iacobelli, M., additional, Juette, E., additional, Karastergiou, A., additional, Klijn, W., additional, Kohler, J., additional, Kondratiev, V. I., additional, Kramer, M., additional, Kuniyoshi, M., additional, Kuper, G., additional, Maat, P., additional, Macario, G., additional, Mann, G., additional, Markoff, S., additional, McKay-Bukowski, D., additional, McKean, J. P., additional, Miller-Jones, J. C. A., additional, Mol, J. D., additional, Mulcahy, D. D., additional, Munk, H., additional, Nijboer, R., additional, Norden, M. J., additional, Orru, E., additional, Overeem, R., additional, Paas, H., additional, Pandey-Pommier, M., additional, Pizzo, R., additional, Polatidis, A. G., additional, Renting, A., additional, Romein, J. W., additional, Röttgering, H., additional, Schoenmakers, A., additional, Schwarz, D., additional, Sluman, J., additional, Smirnov, O., additional, Sobey, C., additional, Stappers, B. W., additional, Steinmetz, M., additional, Swinbank, J., additional, Tang, Y., additional, Tasse, C., additional, Toribio, C., additional, van Leeuwen, J., additional, van Nieuwpoort, R., additional, van Weeren, R. J., additional, Vermaas, N., additional, Vermeulen, R., additional, Vocks, C., additional, Vogt, C., additional, Wijers, R. A. M. J., additional, Wijnholds, S. J., additional, Wise, M. W., additional, Wucknitz, O., additional, Yatawatta, S., additional, Zarka, P., additional, and Zensus, A., additional

Published
2013
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16. The brightness and spatial distributions of terrestrial radio sources

Author

Offringa, A. R., primary, de Bruyn, A. G., additional, Zaroubi, S., additional, Koopmans, L. V. E., additional, Wijnholds, S. J., additional, Abdalla, F. B., additional, Brouw, W. N., additional, Ciardi, B., additional, Iliev, I. T., additional, Harker, G. J. A., additional, Mellema, G., additional, Bernardi, G., additional, Zarka, P., additional, Ghosh, A., additional, Alexov, A., additional, Anderson, J., additional, Asgekar, A., additional, Avruch, I. M., additional, Beck, R., additional, Bell, M. E., additional, Bell, M. R., additional, Bentum, M. J., additional, Best, P., additional, Bîrzan, L., additional, Breitling, F., additional, Broderick, J., additional, Brüggen, M., additional, Butcher, H. R., additional, de Gasperin, F., additional, de Geus, E., additional, de Vos, M., additional, Duscha, S., additional, Eislöffel, J., additional, Fallows, R. A., additional, Ferrari, C., additional, Frieswijk, W., additional, Garrett, M. A., additional, Grießmeier, J., additional, Hassall, T. E., additional, Horneffer, A., additional, Iacobelli, M., additional, Juette, E., additional, Karastergiou, A., additional, Klijn, W., additional, Kondratiev, V. I., additional, Kuniyoshi, M., additional, Kuper, G., additional, van Leeuwen, J., additional, Loose, M., additional, Maat, P., additional, Macario, G., additional, Mann, G., additional, McKean, J. P., additional, Meulman, H., additional, Norden, M. J., additional, Orru, E., additional, Paas, H., additional, Pandey-Pommier, M., additional, Pizzo, R., additional, Polatidis, A. G., additional, Rafferty, D., additional, Reich, W., additional, van Nieuwpoort, R., additional, Röttgering, H., additional, Scaife, A. M. M., additional, Sluman, J., additional, Smirnov, O., additional, Sobey, C., additional, Tagger, M., additional, Tang, Y., additional, Tasse, C., additional, Veen, S. ter, additional, Toribio, C., additional, Vermeulen, R., additional, Vocks, C., additional, van Weeren, R. J., additional, Wise, M. W., additional, and Wucknitz, O., additional

Published
2013
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20. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author

Oonk, J. B. R., van Weeren, R. J., Salgado, F., Morabito, L. K., Tielens, A. G. G. M., Rottgering, H. J. A., Asgekar, A., White, G. J., Alexov, A., Anderson, J., Avruch, I. M., Batejat, F., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., Horst, A. v. d., Iacobelli, M., Jackson, N. J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J. P., Mevius, M., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Scaife, A. M. M., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Veen, S. t., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Oonk, J. B. R., van Weeren, R. J., Salgado, F., Morabito, L. K., Tielens, A. G. G. M., Rottgering, H. J. A., Asgekar, A., White, G. J., Alexov, A., Anderson, J., Avruch, I. M., Batejat, F., Beck, R., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J., Hamaker, J. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., Horst, A. v. d., Iacobelli, M., Jackson, N. J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J. P., Mevius, M., Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pizzo, R., Polatidis, A. G., Reich, W., Scaife, A. M. M., Schoenmakers, A., Schwarz, D., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Stappers, B. W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Veen, S. t., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, A.

22. BOEKBESPREKINGEN

Author

van Doornik, P., primary, Ahsmann, P., additional, Klijn, W., additional, de Strycker, E., additional, Fransen, P., additional, Smulders, P., additional, Vanneste, J., additional, Beyer, J., additional, Ploumen, P., additional, van Kol, A., additional, van Doornik, P., additional, Houben, J. J., additional, Nota, J. H., additional, van Leeuwen, A., additional, Bisschop, L. Steins, additional, Huffer, E., additional, Dupré, L., additional, Geraets, Th. F., additional, De Tollenaere, M., additional, Kijm, J., additional, Braeckmans, L., additional, Kerkhofs, J., additional, Dierickx, M., additional, Van Ommeslaeghe, F., additional, Kerken, L. Vander, additional, and Grootens, P., additional

Published
1959
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23. BOEKBESPREKINGEN

Author

Lambrecht, J., primary, Beuken, W., additional, Tison, J.-M., additional, Fransen, P., additional, van Doornik, P., additional, Vanneste, J., additional, Grootens, P., additional, D'hondt, R., additional, Bakker, L., additional, Arts, H., additional, Van Torre, J., additional, Traets, C., additional, Klijn, W., additional, de Smet, S., additional, Vercruysse, Jos, additional, Houben, Alph., additional, van Leeuwen, H., additional, Boelens, W., additional, Mulders, J., additional, Robbers, H., additional, Somers, H., additional, Kijm, J., additional, Kerkhofs, J., additional, Dierickx, M., additional, Beukers, Cl., additional, and Poncelet, A., additional

Published
1966
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24. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author

J. van Enst, D. Engels, J. B. R. Oonk, S. ter Veen, Tim Hassall, Leah K. Morabito, M. A. Garrett, Alexander G. G. M. Tielens, Ashish Asgekar, J. M. Anderson, Rainer Beck, D. D. Mulcahy, Neal Jackson, Frank Breitling, Vishambhar Pandey, Harvey Butcher, Rob Fender, James Miller-Jones, M. Pandey-Pommier, Sarod Yatawatta, Giulia Macario, Michel Tagger, J. Kohler, Anton Zensus, John Conway, H. J. A. Röttgering, Heino Falcke, H. Munk, Marcus Brüggen, A. Horneffer, Richard Fallows, Jochen Eislöffel, E. Juette, Olaf Wucknitz, P. Maat, M. J. Norden, A. Alexov, C. Vogt, Aris Karastergiou, Maaijke Mevius, G. Kuper, S. Duscha, V. I. Kondratiev, Michael W. Wise, Gianni Bernardi, Philip Best, Benjamin Stappers, Dominik J. Schwarz, Wilfred Frieswijk, Y. Tang, A. Shulevski, Anna M. M. Scaife, Chiara Ferrari, Glenn J. White, B. Ciardi, Marco Iacobelli, M. de Vos, Jean-Mathias Grießmeier, A. G. Polatidis, Arthur Corstanje, Matthias Hoeft, J. Sluman, John McKean, C. Tasse, John D. Swinbank, Francisco Salgado, J. W. Broderick, Roberto Pizzo, E. de Geus, Satyendra Thoudam, Ralph A. M. J. Wijers, Christian Vocks, Sera Markoff, C. Toribio, J. D. Mol, M. Kuniyoshi, Annalisa Bonafede, Jason W. T. Hessels, Michiel A. Brentjens, Mark J. Bentum, George Heald, Michael Kramer, J. van Leeuwen, Philippe Zarka, R. van Nieuwpoort, J. P. Hamaker, Charlotte Sobey, Emanuela Orrú, H. Paas, F. Batejat, W. Reich, Oleg Smirnov, F. de Gasperin, I. van Bemmel, Martin Bell, Gottfried Mann, Matthias Steinmetz, I. M. Avruch, R. J. van Weeren, Rene C. Vermeulen, Wouter Klijn, A. J. van der Horst, A. P. Schoenmakers, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Physics-Electronics, Rhodes University, Grahamstown, University of Edinburgh, Universität Hamburg (UHH), Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Radboud University [Nijmegen], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bielefeld, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Oonk, J.B.R., van Weeren, R.J., salgado, F., Morabito, L.K., Tielens, A.G.G.M., Rottgering, H.J.A., Asgekar, A., White, G.J., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Be, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Griemeier, J., Hamaker, J.P., Hassa, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., scaife, A.M.M., schoenmakers, A., schwarz, D., shulevski, A., sluman, J., smirnov, O., Sobey, C., Stappers, B.W., steinmetz, M., swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
[SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astronomy, ISM: structure, Interstellar cloud, EWI-24499, FOS: Physical sciences, Astrophysics, structure-local interstellar matter-radio line, ISM [radio lines], Cygnus A, Absorption (electromagnetic radiation), Optical depth, Astrophysics::Galaxy Astrophysics, ISM, Line (formation), ISM: general, Physics, IsM, radio lines, radio lines: ISM, general [ISM], local interstellar matter, Local standard of rest, Astronomy and Astrophysics, METIS-302715, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, Cassiopeia A, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, General-IsM, structure [ISM], IR-89519, ISM: general ISM: structure local interstellar matter radio lines: ISM
Abstract

We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in the 33 to 57 MHz range. These low frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon $\alpha$ lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2$\times$10$^{-4}$, a line width of 10 km s$^{-1}$ and a velocity of +4 km s$^{-1}$ with respect to the local standard of rest. The associated gas is found to have an electron temperature $T_{e}\sim$ 110 K and density $n_{e}\sim$ 0.06 cm$^{-3}$. These properties imply that the observed carbon $\alpha$ absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3$\sigma$ peak optical depth limit of 1.5$\times$10$^{-4}$ for a 4 km s$^{-1}$ channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3$\sigma$ upper limit of 1.5$\times$10$^{-4}$ for the peak optical depth of these lines for a 4 km s$^{-1}$ channel width., Comment: In press

Published
2014
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25. Interdisciplinary and Collaborative Training in Neuroscience: Insights from the Human Brain Project Education Programme.

Author

Geminiani A, Kathrein J, Yegenoglu A, Vogel F, Armendariz M, Ben-Zion Z, Bogdan PA, Covelo J, Diaz Pier M, Grasenick K, Karasenko V, Klijn W, Kokan T, Lupascu CA, Lührs A, Mahfoud T, Özden T, Pedersen JE, Peres L, Reiten I, Simidjievski N, Ulnicane I, van der Vlag M, Zehl L, Saria A, Diaz-Pier S, and Passecker J

Subjects
Humans, Curriculum trends, Brain physiology, Cooperative Behavior, Interdisciplinary Research trends, Research Personnel education, Neurosciences education, Neurosciences trends
Abstract

Neuroscience education is challenged by rapidly evolving technology and the development of interdisciplinary approaches for brain research. The Human Brain Project (HBP) Education Programme aimed to address the need for interdisciplinary expertise in brain research by equipping a new generation of researchers with skills across neuroscience, medicine, and information technology. Over its ten year duration, the programme engaged over 1,300 experts and attracted more than 5,500 participants from various scientific disciplines in its blended learning curriculum, specialised schools and workshops, and events fostering dialogue among early-career researchers. Key principles of the programme's approach included fostering interdisciplinarity, adaptability to the evolving research landscape and infrastructure, and a collaborative environment with a focus on empowering early-career researchers. Following the programme's conclusion, we provide here an analysis and in-depth view across a diverse range of educational formats and events. Our results show that the Education Programme achieved success in its wide geographic reach, the diversity of participants, and the establishment of transversal collaborations. Building on these experiences and achievements, we describe how leveraging digital tools and platforms provides accessible and highly specialised training, which can enhance existing education programmes for the next generation of brain researchers working in decentralised European collaborative spaces. Finally, we present the lessons learnt so that similar initiatives may improve upon our experience and incorporate our suggestions into their own programme., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Published
2024
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26. Multiscale co-simulation design pattern for neuroscience applications.

Author

Kusch L, Diaz-Pier S, Klijn W, Sontheimer K, Bernard C, Morrison A, and Jirsa V

Abstract

Integration of information across heterogeneous sources creates added scientific value. Interoperability of data, tools and models is, however, difficult to accomplish across spatial and temporal scales. Here we introduce the toolbox Parallel Co-Simulation, which enables the interoperation of simulators operating at different scales. We provide a software science co-design pattern and illustrate its functioning along a neuroscience example, in which individual regions of interest are simulated on the cellular level allowing us to study detailed mechanisms, while the remaining network is efficiently simulated on the population level. A workflow is illustrated for the use case of The Virtual Brain and NEST, in which the CA1 region of the cellular-level hippocampus of the mouse is embedded into a full brain network involving micro and macro electrode recordings. This new tool allows integrating knowledge across scales in the same simulation framework and validating them against multiscale experiments, thereby largely widening the explanatory power of computational models., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Kusch, Diaz-Pier, Klijn, Sontheimer, Bernard, Morrison and Jirsa.)

Published
2024
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27. Exploring Parameter and Hyper-Parameter Spaces of Neuroscience Models on High Performance Computers With Learning to Learn.

Author

Yegenoglu A, Subramoney A, Hater T, Jimenez-Romero C, Klijn W, Pérez Martín A, van der Vlag M, Herty M, Morrison A, and Diaz-Pier S

Abstract

Neuroscience models commonly have a high number of degrees of freedom and only specific regions within the parameter space are able to produce dynamics of interest. This makes the development of tools and strategies to efficiently find these regions of high importance to advance brain research. Exploring the high dimensional parameter space using numerical simulations has been a frequently used technique in the last years in many areas of computational neuroscience. Today, high performance computing (HPC) can provide a powerful infrastructure to speed up explorations and increase our general understanding of the behavior of the model in reasonable times. Learning to learn (L2L) is a well-known concept in machine learning (ML) and a specific method for acquiring constraints to improve learning performance. This concept can be decomposed into a two loop optimization process where the target of optimization can consist of any program such as an artificial neural network, a spiking network, a single cell model, or a whole brain simulation. In this work, we present L2L as an easy to use and flexible framework to perform parameter and hyper-parameter space exploration of neuroscience models on HPC infrastructure. Learning to learn is an implementation of the L2L concept written in Python. This open-source software allows several instances of an optimization target to be executed with different parameters in an embarrassingly parallel fashion on HPC. L2L provides a set of built-in optimizer algorithms, which make adaptive and efficient exploration of parameter spaces possible. Different from other optimization toolboxes, L2L provides maximum flexibility for the way the optimization target can be executed. In this paper, we show a variety of examples of neuroscience models being optimized within the L2L framework to execute different types of tasks. The tasks used to illustrate the concept go from reproducing empirical data to learning how to solve a problem in a dynamic environment. We particularly focus on simulations with models ranging from the single cell to the whole brain and using a variety of simulation engines like NEST, Arbor, TVB, OpenAIGym, and NetLogo., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Yegenoglu, Subramoney, Hater, Jimenez-Romero, Klijn, Pérez Martín, van der Vlag, Herty, Morrison and Diaz-Pier.)

Published
2022
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28. Deploying and Optimizing Embodied Simulations of Large-Scale Spiking Neural Networks on HPC Infrastructure.

Author

Feldotto B, Eppler JM, Jimenez-Romero C, Bignamini C, Gutierrez CE, Albanese U, Retamino E, Vorobev V, Zolfaghari V, Upton A, Sun Z, Yamaura H, Heidarinejad M, Klijn W, Morrison A, Cruz F, McMurtrie C, Knoll AC, Igarashi J, Yamazaki T, Doya K, and Morin FO

Abstract

Simulating the brain-body-environment trinity in closed loop is an attractive proposal to investigate how perception, motor activity and interactions with the environment shape brain activity, and vice versa. The relevance of this embodied approach, however, hinges entirely on the modeled complexity of the various simulated phenomena. In this article, we introduce a software framework that is capable of simulating large-scale, biologically realistic networks of spiking neurons embodied in a biomechanically accurate musculoskeletal system that interacts with a physically realistic virtual environment. We deploy this framework on the high performance computing resources of the EBRAINS research infrastructure and we investigate the scaling performance by distributing computation across an increasing number of interconnected compute nodes. Our architecture is based on requested compute nodes as well as persistent virtual machines; this provides a high-performance simulation environment that is accessible to multi-domain users without expert knowledge, with a view to enable users to instantiate and control simulations at custom scale via a web-based graphical user interface. Our simulation environment, entirely open source, is based on the Neurorobotics Platform developed in the context of the Human Brain Project, and the NEST simulator. We characterize the capabilities of our parallelized architecture for large-scale embodied brain simulations through two benchmark experiments, by investigating the effects of scaling compute resources on performance defined in terms of experiment runtime, brain instantiation and simulation time. The first benchmark is based on a large-scale balanced network, while the second one is a multi-region embodied brain simulation consisting of more than a million neurons and a billion synapses. Both benchmarks clearly show how scaling compute resources improves the aforementioned performance metrics in a near-linear fashion. The second benchmark in particular is indicative of both the potential and limitations of a highly distributed simulation in terms of a trade-off between computation speed and resource cost. Our simulation architecture is being prepared to be accessible for everyone as an EBRAINS service, thereby offering a community-wide tool with a unique workflow that should provide momentum to the investigation of closed-loop embodiment within the computational neuroscience community., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Feldotto, Eppler, Jimenez-Romero, Bignamini, Gutierrez, Albanese, Retamino, Vorobev, Zolfaghari, Upton, Sun, Yamaura, Heidarinejad, Klijn, Morrison, Cruz, McMurtrie, Knoll, Igarashi, Yamazaki, Doya and Morin.)

Published
2022
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29. Brain simulation as a cloud service: The Virtual Brain on EBRAINS.

Author

Schirner M, Domide L, Perdikis D, Triebkorn P, Stefanovski L, Pai R, Prodan P, Valean B, Palmer J, Langford C, Blickensdörfer A, van der Vlag M, Diaz-Pier S, Peyser A, Klijn W, Pleiter D, Nahm A, Schmid O, Woodman M, Zehl L, Fousek J, Petkoski S, Kusch L, Hashemi M, Marinazzo D, Mangin JF, Flöel A, Akintoye S, Stahl BC, Cepic M, Johnson E, Deco G, McIntosh AR, Hilgetag CC, Morgan M, Schuller B, Upton A, McMurtrie C, Dickscheid T, Bjaalie JG, Amunts K, Mersmann J, Jirsa V, and Ritter P

Subjects
Animals, Bayes Theorem, Computer Simulation, Humans, Magnetic Resonance Imaging methods, Mice, Software, Brain diagnostic imaging, Cloud Computing
Abstract

The Virtual Brain (TVB) is now available as open-source services on the cloud research platform EBRAINS (ebrains.eu). It offers software for constructing, simulating and analysing brain network models including the TVB simulator; magnetic resonance imaging (MRI) processing pipelines to extract structural and functional brain networks; combined simulation of large-scale brain networks with small-scale spiking networks; automatic conversion of user-specified model equations into fast simulation code; simulation-ready brain models of patients and healthy volunteers; Bayesian parameter optimization in epilepsy patient models; data and software for mouse brain simulation; and extensive educational material. TVB cloud services facilitate reproducible online collaboration and discovery of data assets, models, and software embedded in scalable and secure workflows, a precondition for research on large cohort data sets, better generalizability, and clinical translation., Competing Interests: Declaration of competing interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Published
2022
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30. ConGen-A Simulator-Agnostic Visual Language for Definition and Generation of Connectivity in Large and Multiscale Neural Networks.

Author

Herbers P, Calvo I, Diaz-Pier S, Robles OD, Mata S, Toharia P, Pastor L, Peyser A, Morrison A, and Klijn W

Abstract

An open challenge on the road to unraveling the brain's multilevel organization is establishing techniques to research connectivity and dynamics at different scales in time and space, as well as the links between them. This work focuses on the design of a framework that facilitates the generation of multiscale connectivity in large neural networks using a symbolic visual language capable of representing the model at different structural levels-ConGen. This symbolic language allows researchers to create and visually analyze the generated networks independently of the simulator to be used, since the visual model is translated into a simulator-independent language. The simplicity of the front end visual representation, together with the simulator independence provided by the back end translation, combine into a framework to enhance collaboration among scientists with expertise at different scales of abstraction and from different fields. On the basis of two use cases, we introduce the features and possibilities of our proposed visual language and associated workflow. We demonstrate that ConGen enables the creation, editing, and visualization of multiscale biological neural networks and provides a whole workflow to produce simulation scripts from the visual representation of the model., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Herbers, Calvo, Diaz-Pier, Robles, Mata, Toharia, Pastor, Peyser, Morrison and Klijn.)

Published
2022
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31. Editorial: Linking experimental and computational connectomics.

Author

Peyser A, Diaz Pier S, Klijn W, Morrison A, and Triesch J

Abstract

Large-scale in silico experimentation depends on the generation of connectomes beyond available anatomical structure. We suggest that linking research across the fields of experimental connectomics, theoretical neuroscience, and high-performance computing can enable a new generation of models bridging the gap between biophysical detail and global function. This Focus Feature on "Linking Experimental and Computational Connectomics" aims to bring together some examples from these domains as a step toward the development of more comprehensive generative models of multiscale connectomes., Competing Interests: Competing Interests: The authors have declared that no competing interests exist., (© 2019 Massachusetts Institute of Technology.)

Published
2019
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