J/A+A/555/A110 Radio images of CIZA J2242.8+5301 (Stroe+, 2013)
Discovery of spectral curvature in the shock downstream region:
CIZA J2242.8+5301.
Stroe A., van Weeren R.J., Intema H.T., Rottgering H.J.A., Brueggen M.,
Hoeft M.
<Astron. Astrophys. 555, A110 (2013)>
=2013A&A...555A.110S 2013A&A...555A.110S
ADC_Keywords: Clusters, galaxy ; Radio sources
Keywords: acceleration of particles - radio continuum: galaxies -
galaxies: clusters: individual: CIZA J2242.8+5301 -
galaxies: clusters: intracluster medium -
cosmology: large-scale structure of Univers
Abstract:
Giant cluster radio relics are thought to form at shock fronts in the
course of collisions between galaxy clusters. Via processes that are
still poorly understood, these shocks accelerate or re-accelerate
cosmic-ray electrons and might amplify magnetic fields. The best
object to study this phenomenon is the galaxy cluster
CIZA J2242.8+5301 as it shows the most undisturbed relic. By means of
Giant Metrewave Radio Telescope (GMRT) and Westerbork Synthesis Radio
Telescope (WSRT) data at seven frequencies spanning from 153MHz to
2272MHz, we study the synchrotron emission in this cluster.
We aim at distinguishing between theoretical injection and
acceleration models proposed for the formation of radio relics. We
also study the head-tail radio sources to reveal the interplay between
the merger and the cluster galaxies.
We produced spectral index, curvature maps, and radio colour-colour
plots and compared our data with predictions from models.
We present one of the deepest 153MHz maps of a cluster ever produced,
reaching a noise level of 1.5mJy/beam. We derive integrated spectra
for four relics in the cluster, discovering extremely steep spectrum
diffuse emission concentrated in multiple patches. We find a possible
radio phoenix embedded in the relic to the south of the cluster. The
spectral index of the northern relic retains signs of steepening from
the front towards the back of the shock also at the radio frequencies
below 600MHz. The spectral curvature in the same relic also increases
in the downstream area. The data is consistent with the
Komissarov-Gubanov injection models, meaning that the emission we
observe is produced by a single burst of spectrally-aged accelerated
radio electrons.
Description:
A collection of seven radio images of the merging cluster CIZA
J2242.8+5301, which hosts a pair of giant radio relics. The data were
taken at the WSRT and GMRT radio telescopes.
Objects:
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RA (2000) DE Designation(s)
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22 42 51.0 +53 01 24 CIZA J2242.8+5301 = NAME Sausage cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 58 7 Summary of fits images
fits/* . 7 Individual FITS images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 F3.1 arcsec/pix Scale Scale of the image
24- 27 I4 pix Nx Number of pixels along X-axis
28 A1 --- --- [x]
29- 32 I4 pix Ny Number of pixels along Y-axis
34- 44 f11.9 GHz Freq Frequency
46- 58 A13 --- FileName Name of FITS file in subdirectory fits
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Acknowledgements:
Andra Stroe, astroe(at)strw.leidenuniv.nl
(End) Andra Stroe [Leiden Observatory], Patricia Vannier [CDS] 14-Jun-2013