The power-law behaviours of angular spectra of polarized Galactic synchrotron |
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| Institution: | 1. Dipartimento di Astronomia, Università di Firenze, Largo Fermi 2, I-50125 Firenze, Italy;2. Dipartimento di Fisica, Università di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy;3. I.R.A./C.N.R., Sezione di Firenze, Largo Fermi 5, I-50125 Firenze, Italy;4. I.A.S.F./C.N.R., Sezione di Bologna, Via P. Gobetti 101, I-40129 Bologna, Italy;5. Dipartimento di Fisica, Università di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino, Italy;2. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121, Bonn, Germany;3. Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, California, 94720;1. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-5300 Bonn 1, F.R.G.;2. Erstes Physikalisches Institut, Universität zu Köln, Universitätsstrasse 14, D-5000 Köln 41, F.R.G.;3. National Radio Astronomy Observatory, VLA Program, PO Box 0, Soccorro, NM 87801, U.S.A.;1. Department of Mechanical and Naval Engineering, Faculty of Engineering, University of Buenos Aires, Paseo Colón 850, 1063 Buenos Aires, Argentina;1. University of Manchester, Jodrell Bank Observatory, SK11 9DL Cheshire, UK;2. Max-Planck-Institut für Radioastronomie, Postfach 2024, 53010 Bonn, Germany |
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| Abstract: | We study the angular power spectra of polarized Galactic synchrotron in the range 10?l≤800, at several frequencies between 0.4 and 2.7 GHz and at several Galactic latitudes up to near the North Galactic Pole. Electric- and magnetic-parity polarization spectra are found to have slopes around αE,B=1.4–1.5 in the Parkes and Effelsberg Galactic-Plane surveys, but strong local fluctuations of αE,B are found at |b|?10° from the 1.4 GHz Effelsberg survey. The CPIl spectrum, which is insensitive to the polarization direction, is somewhat steeper, being αPI=1.6–1.8 for the same surveys. The low-resolution multifrequency survey of Brouw and Spoelstra A&AS 26 (1976) 129] shows some flattening of the spectra below 1 GHz, more intense for CE,Bl than for CPIl. In no case we find evidence for really steep spectra. The extrapolation to the cosmological window shows that at 90 GHz the detection of E-mode harmonics in the cosmic background radiation should not be disturbed by synchrotron, even around l?10 for a reionization optical depth τri?0.05. |
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