LOFAR, VLA, AND CHANDRA OBSERVATIONS OF THE TOOTHBRUSH GALAXY CLUSTER
Artikel i vetenskaplig tidskrift, 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.

Författare

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

Universiteit Leiden

Netherlands Institute for Radio Astronomy (ASTRON)

University of Hertfordshire

H. Rottgering

Universiteit Leiden

W. A. Dawson

Lawrence Livermore National Laboratory

W. R. Forman

Harvard-Smithsonian Center for Astrophysics

F. De Gasperin

Universität Hamburg

Universiteit Leiden

M. J. Hardcastle

University of Hertfordshire

C. G. Jones

Harvard-Smithsonian Center for Astrophysics

G. K. Miley

Universiteit Leiden

D. Rafferty

Universität Hamburg

L. Rudnick

University of Minnesota System

J. Sabater

University of Edinburgh

C. L. Sarazin

University of Virginia

T. W. Shimwell

Universiteit Leiden

A. Bonafede

Universität Hamburg

P. N. Best

University of Edinburgh

L. Birzan

Universität Hamburg

R. Cassano

Istituto di Radioastronomia

K.T. Chyz̊y

Uniwersytet Jagiellonski w Krakowie

J. H. Croston

University of Southampton

T. J. Dijkema

Netherlands Institute for Radio Astronomy (ASTRON)

T.A. Enßlin

Max Planck-institutet

C. Ferrari

Observatoire de la Cote d'Azur

G. Heald

Netherlands Institute for Radio Astronomy (ASTRON)

Rijksuniversiteit Groningen

M. Hoeft

Thüringer Landessternwarte Tautenburg

Cathy Horellou

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

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

Universiteit Leiden

National Radio Astronomy Observatory

S. S. Murray

Harvard-Smithsonian Center for Astrophysics

Johns Hopkins University

E. Orru

Netherlands Institute for Radio Astronomy (ASTRON)

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

S. S. Sridhar

Rijksuniversiteit Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

A. Simionescu

JAXA Institute of Space and Astronautical Science

A. Stroe

Universiteit Leiden

S. van der Tol

Netherlands Institute for Radio Astronomy (ASTRON)

G. J. White

Open University

Rutherford Appleton Laboratory

Astrophysical Journal

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

Vol. 818 204

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

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