Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz

H. K. Vedantham, L. V. E. Koopmans, A. G. de Bruyn, S. J. Wijnholds, M. Brentjens, F. B. Abdalla, K. M. B. Asad, G. Bernardi, S. Bus, E. Chapman, B. Ciardi, S. Daiboo, E. R. Fernandez, A. Ghosh, G. Harker, V. Jelic, H. Jensen, S. Kazemi, P. Lambropoulos, O. Martinez-RubiG. Mellema, M. Mevius, A. R. Offringa, V. N. Pandey, A. H. Patil, R. M. Thomas, V. Veligatla, S. Yatawatta, S. Zaroubi, J. Anderson, A. Asgekar, M. E. Bell, M. J. Bentum, P. Best, A. Bonafede, F. Breitling, J. Broderick, M. Brüggen, H. R. Butcher, A. Corstanje, F. de Gasperin, E. de Geus, A. Deller, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. A. Fallows, R. Fender, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, T. E. Hassall, G. Heald, M. Hoeft, J. Hörandel, M. Iacobelli, E. Juette, V. I. Kondratiev, M. Kuniyoshi, G. Kuper, G. Mann, S. Markoff, R. McFadden, D. McKay-Bukowski, J. P. McKean, D. D. Mulcahy, H. Munk, A. Nelles, M. J. Norden, E. Orru, M. Pandey-Pommier, R. Pizzo, A. G. Polatidis, W. Reich, A. Renting, H. Röttgering, D. Schwarz, A. Shulevski, O. Smirnov, B. W. Stappers, M. Steinmetz, J. Swinbank, M. Tagger, Y. Tang, C. Tasse, S. ter Veen, S. Thoudam, C. Toribio, C. Vocks, M. W. Wise, O. Wucknitz, P. Zarka

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We present radio observations of the Moon between 35 and 80 MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies 35 <ν <80 MHz since it is `colder' than the diffuse Galactic background it occults, (ii) using the (negative) flux of the lunar disc, we can reconstruct the spectrum of the diffuse Galactic emission with the lunar thermal emission as a reference, and (iii) that reflected RFI (radio-frequency interference) is concentrated at the centre of the lunar disc due to specular nature of reflection, and can be independently measured. Our RFI measurements show that (i) Moon-based Cosmic Dawn experiments must design for an Earth-isolation of better than 80 dB to achieve an RFI temperature z > 12) and the Epoch of Reionization (12 > z > 5).
Originele taal-2English
Pagina's (van-tot)2291-2305
TijdschriftMonthly Notices of the Royal Astronomical Society
Nummer van het tijdschrift3
StatusPublished - 1-jul.-2015

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