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

Vedantham HK, Koopmans LVE, De Bruyn AG, Wijnholds SJ, Brentjens M, Abdalla FB, Asad KMB, Bernardi G, Bus S, Chapman E, Ciardi B, Daiboo S, Fernandez ER, Ghosh A, Harker GJ, Jelic V, Jensen H, Kazemi S, Lambropoulos P, Martinez-Rubi O, Mellema G, Mevius M, Offringa AR, Pandey VN, Patil AH, Thomas RM, Veligatla V, Yatawatta S, Zaroubi S, Anderson J, Asgekar A, Bell ME, Bentum MJ, Best P, Bonafede A, Breitling F, Broderick J, Bruggen M, Butcher HR, Corstanje A, De Gasperin F, De Geus E, Deller A, Duscha S, Eisloeffel J, Engels D, Falcke H, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Griessmeier J, Gunst AW, Hassall TE, Heald G, Hoeft M, Hoerandel J, Iacobelli M, Juette E, Kondratiev VI, Kuniyoshi M, Kuper G, Mann G, Markoff S, Mcfadden R, Mckay-Bukowski D, Mckean JP, Mulcahy DD, Munk H, Nelles A, Norden MJ, Orru E, Pandey-Pommier M, Pizzo R, Polatidis AG, Reich W, Renting A, Roettgering H, Schwarz D, Shulevski A, Smirnov O, Stappers BW, Steinmetz M, Swinbank J, Tagger M, Tang Y, Tasse C, Ter Veen S, Thoudam S, Toribio C, Vocks C, Wise MW, Wucknitz O, Zarka P (2015)

Publication Status: Published

Publication Type: Journal article

Publication year: 2015

Journal

Publisher: OXFORD UNIV PRESS

Book Volume: 450

Pages Range: 2291-2305

Journal Issue: 3

DOI: 10.1093/mnras/stv746

Abstract

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 < nu < 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 < 1 mK, (ii) Moon-reflected RFI contributes to a dipole temperature less than 20 mK for Earth-based Cosmic Dawn experiments, (iii) man-made satellite-reflected RFI temperature exceeds 20 mK if the aggregate scattering cross-section of visible satellites exceeds 175 m(2) at 800 km height, or 15 m(2) at 400 km height. Currently, our diffuse background spectrum is limited by sidelobe confusion on short baselines (10-15 per cent level). Further refinement of our technique may yield constraints on the redshifted global 21 cm signal from Cosmic Dawn (40 > z > 12) and the Epoch of Reionization (12 > z > 5).

Authors with CRIS profile

Involved external institutions

Universität Hamburg (UHH) Germany (DE) LPC2E France (FR) University of Oxford United Kingdom (GB) Netherlands Institute for Radio Astronomy Netherlands (NL) University of Southampton United Kingdom (GB) University of Groningen / Rijksuniversiteit Groningen Netherlands (NL) Leibniz Institute for Astrophysics Potsdam / Leibniz-Institut für Astrophysik Potsdam Germany (DE) SKA South Africa South Africa (ZA) Australia Telescope National Facility (ATNF) Australia (AU) Stockholm University / Stockholms universitet Sweden (SE) Australian National University (ANU) Australia (AU) University of Edinburgh United Kingdom (GB) Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ Germany (DE) University College London (UCL) United Kingdom (GB) Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. (MPG) / Max Planck Society for the Advancement of Science Germany (DE) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) Leiden University Netherlands (NL) Radboud University Nijmegen Netherlands (NL) University of Amsterdam Netherlands (NL) Oulun Yliopisto / University of Oulo Finland (FI) University of Manchester United Kingdom (GB) Universität Bielefeld Germany (DE) Observatoire de Lyon France (FR) Thüringer Landessternwarte Tautenburg (TLS) - Karl-Schwarzschild-Observatorium Germany (DE) University of Nice Sophia Antipolis / Université Nice Sophia Antipolis France (FR) Ruhr-Universität Bochum (RUB) Germany (DE) PSL Research University / Université de recherche Paris Sciences et Lettres France (FR)

How to cite

APA:

Vedantham, H.K., Koopmans, L.V.E., De Bruyn, A.G., Wijnholds, S.J., Brentjens, M., Abdalla, F.B.,... Zarka, P. (2015). Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz. Monthly Notices of the Royal Astronomical Society, 450(3), 2291-2305. https://doi.org/10.1093/mnras/stv746

MLA:

Vedantham, H. K., et al. "Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz." Monthly Notices of the Royal Astronomical Society 450.3 (2015): 2291-2305.

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