Studying Galactic interstellar turbulence through fluctuations in synchrotron emission
- Creators
- Iacobelli, M.
- Haverkorn, M.
- Orrú, E.
- Pizzo, R. F.
- Anderson, J.
- Beck, R.
- Bell, M. R.
- Bonafede, A.
- Chyzy, K.
- Dettmar, R.-J.
- Ensslin, T. A.
- Heald, G.
- Horellou, C.
- Horneffer, A.
- Jurusik, W.
- Junklewitz, H.
- Kuniyoshi, M.
- Mulcahy, D. D.
- Paladino, R.
- Reich, W.
- Scaife, A.
- Sobey, C.
- Sotomayor-Beltran, C.
- Alexov, A.
- Bell, M. E.
- Asgekar, A.
- Avruch, I. M.
- van Bemmel, I.
- Bentum, M. J.
- Bernardi, G.
- Best, P.
- Birzan, L.
- Breitling, F.
- Broderick, J.
- Brouw, W. N.
- Brüggen, M.
- Butcher, H. R.
- Ciardi, B.
- Conway, J. E.
- de Gasperin, F.
- de Geus, E.
- Duscha, S.
- Eislöffel, J.
- Engels, D.
- Falcke, H.
- Fallows, R. A.
- Ferrari, C.
- Frieswijk, W.
- Garrett, M. A.
- Griessmeier, Jean-Mathias
- Gunst, A. W.
- Hamaker, J. P.
- Hassall, T. E.
- Hessels, J. W. T.
- Hoeft, M.
- Hörandel, J.
- Jelic, V.
- Karastergiou, A.
- Kondratiev, V. I.
- Koopmans, L. V. E.
- Kramer, M.
- Kuper, G.
- van Leeuwen, J.
- Macario, G.
- Mann, G.
- Mckean, J. P.
- Munk, H.
- Pandey-Pommier, M.
- Polatidis, A. G.
- Röttgering, H.
- Schwarz, D.
- Sluman, J.
- Smirnov, O.
- Stappers, B. W.
- Steinmetz, M.
- Tagger, Michel
- Tang, Y.
- Tasse, C.
- Toribio, C.
- Vermeulen, R.
- Vocks, C.
- Vogt, C.
- van Weeren, R. J.
- Wise, M. W.
- Wucknitz, O.
- Yatawatta, S.
- Zarka, P.
- Zensus, A.
- Others:
- Leiden Observatory [Leiden] ; Universiteit Leiden [Leiden]
- Netherlands Institute for Radio Astronomy (ASTRON)
- Radboud University [Nijmegen]
- Max-Planck-Institut für Radioastronomie (MPIFR)
- Max Planck Institute for Astrophysics ; Max-Planck-Gesellschaft
- Jacobs University [Bremen]
- Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ)
- Astronomisches Institut der Ruhr-Universität Bochum ; Ruhr-Universität Bochum [Bochum]
- Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO)
- School of Physics and Astronomy [Southampton] ; University of Southampton
- Sydney Institute for Astronomy (SIfA) ; The University of Sydney
- SRON Netherlands Institute for Space Research (SRON)
- Harvard-Smithsonian Center for Astrophysics (CfA) ; Harvard University [Cambridge]-Smithsonian Institution
- University of Edinburgh
- Leibniz-Institut für Astrophysik Potsdam (AIP)
- Kapteyn Astronomical Institute [Groningen] ; University of Groningen [Groningen]
- Onsala Space Observatory (OSO) ; Chalmers University of Technology [Göteborg]
- Medstar Research Institute ; Medstar Research Institute
- Thüringer Landessternwarte Tautenburg (TLS)
- Hamburger Sternwarte/Hamburg Observatory ; Universität Hamburg (UHH)
- Joseph Louis LAGRANGE (LAGRANGE) ; Université Nice Sophia Antipolis (1965 - 2019) (UNS) ; COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur ; COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
- Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E) ; Observatoire des Sciences de l'Univers en région Centre (OSUC) ; Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Paris] (CNES)
- Jodrell Bank Centre for Astrophysics ; University of Manchester [Manchester]
- University of Amsterdam [Amsterdam] (UvA)
- Oxford Astrophysics ; University of Oxford
- University of Groningen [Groningen]
- Université de Nice Sophia-Antipolis (UNSA)
- Centre de Recherche Astrophysique de Lyon (CRAL) ; École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL) ; Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Universität Bielefeld
- Rhodes University, Grahamstown
- SKA South Africa ; Ska South Africa
- Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA) ; Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
- Astronomical Institute Anton Pannekoek (AI PANNEKOEK) ; University of Amsterdam [Amsterdam] (UvA)
- Argelander-Institut für Astronomie (AlfA) ; Rheinische Friedrich-Wilhelms-Universität Bonn
- Observatoire de Paris - Site de Paris (OP) ; Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)
- This work is part of the research programme 639.042.915, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO).
- European Project: 239490,EC:FP7:PEOPLE,FP7-PEOPLE-IRG-2008,MAGNETIC_MILKYWAY(2009)
Description
Aims: The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters.Methods: We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) ~ (137.0°, +7.0°) at 80' × 70' resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations.Results: We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = -1.84 ± 0.19. We find an upper limit of ~20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes.Conclusions. We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ -1.84 up to angular multipoles of ≤1300, corresponding to an angular scale of ~8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence (Lout) of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates.
Abstract
International audience
Additional details
- URL
- https://hal-insu.archives-ouvertes.fr/insu-01288769
- URN
- urn:oai:HAL:insu-01288769v1
- Origin repository
- UNICA