LOFAR, VLA, AND CHANDRA OBSERVATIONS OF THE TOOTHBRUSH GALAXY CLUSTER
Journal article, 2016
We present deep LOFAR observations between 120 and 181 MHz of the "Toothbrush" (RX J0603.3+ 4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of alpha = -0.8 +/- 0.1 at the northern edge of the main radio relic, steepening toward the south to alpha approximate to-2. The spectral index of the radio halo is remarkably uniform (alpha = -1.16, with an intrinsic scatter of <= 0.04). The observed radio relic spectral index gives a Mach number of M = 2.8(-0.3)(+0.5), assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock (M approximate to 1.2, with an upper limit of M approximate to 1.5). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.
Author
R. J. van Weeren
Harvard-Smithsonian Center for Astrophysics
G. Brunetti
Istituto Di Radioastronomia, Bologna
M. Brüggen
Universitat Hamburg
F. Andrade-Santos
Harvard-Smithsonian Center for Astrophysics
G. Ogrean
Harvard-Smithsonian Center for Astrophysics
W. L. Williams
University of Hertfordshire
Netherlands Foundation for Research in Astronomy
Leiden Observatory Research Institute
H. Rottgering
Leiden Observatory Research Institute
W. A. Dawson
Lawrence Livermore National Laboratory
W. R. Forman
Harvard-Smithsonian Center for Astrophysics
F. De Gasperin
Leiden Observatory Research Institute
Universitat Hamburg
M. J. Hardcastle
University of Hertfordshire
C. G. Jones
Harvard-Smithsonian Center for Astrophysics
G. K. Miley
Leiden Observatory Research Institute
D. Rafferty
Universitat Hamburg
L. Rudnick
University of Minnesota System
J. Sabater
University of Edinburgh
C. L. Sarazin
University of Virginia
T. W. Shimwell
Leiden Observatory Research Institute
A. Bonafede
Universitat Hamburg
P. N. Best
University of Edinburgh
L. Birzan
Universitat Hamburg
R. Cassano
Istituto Di Radioastronomia, Bologna
K.T. Chyz̊y
Uniwersytet Jagiellonski w Krakowie
J. H. Croston
University of Southampton
T. J. Dijkema
Netherlands Foundation for Research in Astronomy
T.A. Enßlin
Max Planck Institut fur Astrophysik
C. Ferrari
Observatoire de la Cote d'Azur
G. Heald
University of Groningen, Kapteyn Astronomical Institute
Netherlands Foundation for Research in Astronomy
M. Hoeft
Thuringer Landessternwarte Tautenburg
Cathy Horellou
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
M. J. Jarvis
University of Oxford
University of the Western Cape
R. P. Kraft
Harvard-Smithsonian Center for Astrophysics
M. Mevius
Netherlands Foundation for Research in Astronomy
H. T. Intema
Leiden Observatory Research Institute
National Radio Astronomy Observatory
S. S. Murray
Harvard-Smithsonian Center for Astrophysics
Johns Hopkins University
E. Orru
Netherlands Foundation for Research in Astronomy
R. Pizzo
Netherlands Foundation for Research in Astronomy
S. S. Sridhar
University of Groningen, Kapteyn Astronomical Institute
Netherlands Foundation for Research in Astronomy
A. Simionescu
JAXA Institute of Space and Astronautical Science
A. Stroe
Leiden Observatory Research Institute
S. van der Tol
Netherlands Foundation for Research in Astronomy
G. J. White
Rutherford Appleton Laboratory
Open University
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 818 2 204Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.3847/0004-637x/818/2/204