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

M. Brüggen

Universität Hamburg

F. Andrade-Santos

Harvard-Smithsonian Center for Astrophysics

G. Ogrean

Harvard-Smithsonian Center for Astrophysics

W. L. Williams

Netherlands Institute for Radio Astronomy (ASTRON)

University of Hertfordshire

Leiden University

H. Rottgering

Leiden University

W. A. Dawson

Lawrence Livermore National Laboratory

W. R. Forman

Harvard-Smithsonian Center for Astrophysics

F. De Gasperin

Leiden University

Universität Hamburg

M. J. Hardcastle

University of Hertfordshire

C. G. Jones

Harvard-Smithsonian Center for Astrophysics

G. K. Miley

Leiden University

D. Rafferty

Universität Hamburg

L. Rudnick

University of Minnesota

J. Sabater

University of Edinburgh

C. L. Sarazin

University of Virginia

T. W. Shimwell

Leiden University

A. Bonafede

Universität Hamburg

P. N. Best

University of Edinburgh

L. Birzan

Universität Hamburg

R. Cassano

Istituto di Radioastronomia

K.T. Chyz̊y

Jagiellonian University in Kraków

J. H. Croston

University of Southampton

T. J. Dijkema

Netherlands Institute for Radio Astronomy (ASTRON)

T.A. Enßlin

Max Planck Society

C. Ferrari

Observatoire de la Cote d'Azur

G. Heald

Netherlands Institute for Radio Astronomy (ASTRON)

University of Groningen

M. Hoeft

Thüringer 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 Institute for Radio Astronomy (ASTRON)

H. T. Intema

Leiden University

National Radio Astronomy Observatory

S. S. Murray

Johns Hopkins University

Harvard-Smithsonian Center for Astrophysics

E. Orru

Netherlands Institute for Radio Astronomy (ASTRON)

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

S. S. Sridhar

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

A. Simionescu

JAXA Institute of Space and Astronautical Science

A. Stroe

Leiden University

S. van der Tol

Netherlands Institute for Radio Astronomy (ASTRON)

G. J. White

Rutherford Appleton Laboratory

Open University

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 818 2 204

Subject Categories

Astronomy, Astrophysics and Cosmology

Roots

Basic sciences

DOI

10.3847/0004-637x/818/2/204

More information

Latest update

4/15/2019