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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-Wroczy´nski, 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, Satyendra, Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., Wucknitz, O., Yatawatta, S., Zarka, P., 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-Wroczy´nski, 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, Satyendra, Vermeulen, R., Vocks, C., Vogt, C., Wijers, R. A. M. J., 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
Full Text: View/download PDF

2. 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., Zarka, P., 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.
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
Full Text: View/download PDF

3. 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., Zarka, P., 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.
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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4. 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

5. 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
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6. 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., 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., 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.
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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7. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author: Oonk, J. B. R., van Weeren, R. J., Salgado, Francisco, Morabito, Leah K., Tielens, Alexander G. G. M., Rottgering, Hubb, Asgekar, A, White, Glenn J., Alexov, A., Anderson, J. M., Avruch, Ian M., Batejat, F., Beck, Rainer, Bell, M. E., van Bemmel, Illse, Bentum, M. J., Bernardi, Gianni, Best, Phillip, Bonafede, A., Breitling, F., Brentjens, Michiel A., Broderick, J., Bruggen, M, Butcher, Harvey, Ciardi, Benedetta, Conway, J. E., Corstanje, Arthur, de Gasperin, F., de Geus, Eugene, de Vos, Marco, Duscha, S., Eisloffel, Jochen, Engels, Dieter, Van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Hamaker, Johan P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, Andreas, Van Der Horst, Alexander, Iacobelli, M., Jackson, Neal, Juette, E., Karastergiou, A., Klijn, W., Kohler, Jens, Kondratiev, V. I., Kramer, M, Kuniyoshi, M, Kuper, G., van Leeuwen, J, Maat, P, Macario, Giulia, Mann, Gottfried, Markoff, Sera, McKean, J P, Mevius, Maaijke, Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D.D., Munk, H, Norden, M J, Orru, Emanuela, Paas, H., Pandey-Pommier, Mamta, Pandey, V N, Pizzo, R, Polatidis, A.G., Reich, W, Scaife, Anna, Schoenmakers, Arno, Schwarz, Dominik, Shulevski, Alexander, Sluman, J, Smirnov, O, Sobey, C, Stappers, B. W., Steinmetz, M., Swinbank, J, Tagger, Michel, Tang, Y, Tasse, C, Ter Veen, Sander, Thoudam, Satyendra, Toribio, C., Van Nieuwpoort, Rob, Vermeulen, R.C., Vocks, Christian, Yatawatta, S, Oonk, J. B. R., van Weeren, R. J., Salgado, Francisco, Morabito, Leah K., Tielens, Alexander G. G. M., Rottgering, Hubb, Asgekar, A, White, Glenn J., Alexov, A., Anderson, J. M., Avruch, Ian M., Batejat, F., Beck, Rainer, Bell, M. E., van Bemmel, Illse, Bentum, M. J., Bernardi, Gianni, Best, Phillip, Bonafede, A., Breitling, F., Brentjens, Michiel A., Broderick, J., Bruggen, M, Butcher, Harvey, Ciardi, Benedetta, Conway, J. E., Corstanje, Arthur, de Gasperin, F., de Geus, Eugene, de Vos, Marco, Duscha, S., Eisloffel, Jochen, Engels, Dieter, Van Enst, J., Falcke, H., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Hamaker, Johan P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, Andreas, Van Der Horst, Alexander, Iacobelli, M., Jackson, Neal, Juette, E., Karastergiou, A., Klijn, W., Kohler, Jens, Kondratiev, V. I., Kramer, M, Kuniyoshi, M, Kuper, G., van Leeuwen, J, Maat, P, Macario, Giulia, Mann, Gottfried, Markoff, Sera, McKean, J P, Mevius, Maaijke, Miller-Jones, J. C. A., Mol, J. D., Mulcahy, D.D., Munk, H, Norden, M J, Orru, Emanuela, Paas, H., Pandey-Pommier, Mamta, Pandey, V N, Pizzo, R, Polatidis, A.G., Reich, W, Scaife, Anna, Schoenmakers, Arno, Schwarz, Dominik, Shulevski, Alexander, Sluman, J, Smirnov, O, Sobey, C, Stappers, B. W., Steinmetz, M., Swinbank, J, Tagger, Michel, Tang, Y, Tasse, C, Ter Veen, Sander, Thoudam, Satyendra, Toribio, C., Van Nieuwpoort, Rob, Vermeulen, R.C., Vocks, Christian, and Yatawatta, S
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
Published: 2014

8. 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., 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., 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.
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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9. 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

10. 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, Garrelt, 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., Birzan, L., Breitling, F., Broderick, J., Brueggen, M., Butcher, H. R., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloeffel, 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., Roettgering, 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., Wucknitz, O., 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, Garrelt, 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., Birzan, L., Breitling, F., Broderick, J., Brueggen, M., Butcher, H. R., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eisloeffel, 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., Roettgering, 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.
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 30-163 MHz 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., AuthorCount:78
Published: 2013
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11. 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., Zensus, A., 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.
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
Full Text: View/download PDF

12. 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., Wucknitz, O., 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.
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
Full Text: View/download PDF

13. 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

14. 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., Zensus, A., 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.
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
Full Text: View/download PDF

15. 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., Wucknitz, O., 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.
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
Full Text: View/download PDF

16. 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, Satyendra, van den Akker, M., 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., Zensus, A., 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, Satyendra, van den Akker, M., 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.
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 ~2 years of observing, 405 cosmic-ray events in the energy range of 1016−1018 eV have been detected in the band from 30−80 MHz. Each of these air showers is registered with up to ~1000 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
Full Text: View/download PDF

17. 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

18. Detecting cosmic rays with the LOFAR radio telescope

Author: Schellart, P., Nelles, A., Buitink, S., Corstanje, A., Enriquez, J., Falcke, H., Frieswijk, W., Horandel, J., Horneffer, A., James, C., Krause, M., Mevius, M., Scholten, O., ter Veen, S., Thoudam, S., Van den Akker, M., Alexov, A., Anderson, J., Avruch, I., Bahren, L., Beck, R., Bell, M., Bennema, P., Bentum, M., BERNARDI, G., Best, P., Bregman, J., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Ciardi, B., Coolen, A., de Gasperin, F., de Geus, E., de Jong, A., de Vos, M., Duscha, S., Eisloffel, J., Fallows, R., Ferrari, C., Garrett, M., Grießmeier, J., Grit, T., Hamaker, J., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Holties, H., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., McKean, J., Miller-Jones, James, Mol, J., Mulcahy, D., Munk, H., Nijboer, R., Norden, M., Orru, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A., Renting, G., Romein, J., Rottgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tang, Y., Tasse, C., Toribio, M., van Leeuwen, J., Wijnholds, S., Wise, M., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, J., Schellart, P., Nelles, A., Buitink, S., Corstanje, A., Enriquez, J., Falcke, H., Frieswijk, W., Horandel, J., Horneffer, A., James, C., Krause, M., Mevius, M., Scholten, O., ter Veen, S., Thoudam, S., Van den Akker, M., Alexov, A., Anderson, J., Avruch, I., Bahren, L., Beck, R., Bell, M., Bennema, P., Bentum, M., BERNARDI, G., Best, P., Bregman, J., Breitling, F., Brentjens, M., Broderick, J., Bruggen, M., Ciardi, B., Coolen, A., de Gasperin, F., de Geus, E., de Jong, A., de Vos, M., Duscha, S., Eisloffel, J., Fallows, R., Ferrari, C., Garrett, M., Grießmeier, J., Grit, T., Hamaker, J., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Holties, H., Iacobelli, M., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., McKean, J., Miller-Jones, James, Mol, J., Mulcahy, D., Munk, H., Nijboer, R., Norden, M., Orru, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A., Renting, G., Romein, J., Rottgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tang, Y., Tasse, C., Toribio, M., van Leeuwen, J., Wijnholds, S., Wise, M., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, J.
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 2 years of observing, 405 cosmic-ray events in the energy range of 1016??1018 eV have been detected in the band from 30??80 MHz. Each of these air showers is registered with up to 1000 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

19. 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.

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

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19 results on '"Klijn, W."'

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