Turbulent magnetic fields in the merging galaxy cluster MACS J0717.5+3745: polarization analysis

Abstract

We present wideband polarimetric observations, obtained with the Karl G. Jansky Very Large Array (VLA), of the merging galaxy cluster MACS J0717.5+3745, which hosts one of the most complex known radio relic and halo systems. We use both Rotation Measure Synthesis and QU-fitting, and find a reasonable agreement of the results obtained with these methods, in particular, when the Faraday distribution is simple and the depolarization is mild. The relic is highly polarized over its entire length reaching a fractional polarization $>30\%$ in some regions. We also observe a strong wavelength-dependent depolarization for some regions of the relic. The northern part of the relic shows a complex Faraday distribution suggesting that this region is located in or behind the intracluster medium (ICM). Conversely, the southern part of the relic shows a Rotation Measure very close to the Galactic foreground, with a rather low Faraday dispersion, indicating very little magnetoionic material intervening the line-of-sight. From spatially resolved polarization analysis, we find that the scatter of Faraday depths correlates with the depolarization, indicating that the tangled magnetic field in the ICM causes the depolarization. At the position of a well known narrow-angle-tailed galaxy (NAT), we find evidence of two components clearly separated in Faraday space. The high Faraday dispersion component seems to be associated with the NAT, suggesting the NAT is embedded in the ICM while the southern part of the relic lies in front of it. The magnetic field orientation follows the relic structure indicating a well-ordered magnetic field. We also detect polarized emission in the halo region; however the absence of significant Faraday rotation and a low value of Faraday dispersion suggests the polarized emission, previously considered as the part of the halo, has a shock(s) origin.

22 pages, 19 figures, accepted for publication in A&A

References in corpus (27)

• The NumPy array: a structure for efficient numerical computation
• Diffuse Radio Emission from Galaxy Clusters
• Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster
• Radio signature of cosmological structure formation shocks
• The Case for Electron Re-Acceleration at Galaxy Cluster Shocks
• Resolved magnetic dynamo action in the simulated intracluster medium
• Deep VLA observations of the cluster 1RXS J0603.3+4214 in the frequency range 1-2 GHz
• A $\mathcal{M}\gtrsim 3$ shock in `El Gordo' cluster and the origin of the radio relic
• Dynamical evolution of magnetic fields in the intracluster medium
• Wideband VLA Observations of Abell 2256 I: Continuum, Rotation Measure and Spectral Imaging
• Testing cosmic-ray acceleration with radio relics: a high-resolution study using MHD and tracers
• VLA Radio Observations of the HST Frontier Fields Cluster Abell 2744: The Discovery of New Radio Relics
• Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis
• Relics in galaxy clusters at high radio frequencies
• Chandra and JVLA observations of HST Frontier Fields cluster MACS J0717.5+3745
• Morphology of radio relics I: What causes the substructure of synchrotron emission?
• Physical insights from the spectrum of the radio halo in MACS J0717.5+3745
• Polarisation of Radio Relics in Galaxy Clusters
• The intra-cluster magnetic field in the double relic galaxy cluster Abell 2345
• Understanding the radio relic emission in the galaxy cluster MACS J0717.5+3745: spectral analysis
• Observations of the galaxy cluster CIZA J2242.8+5301 with the Sardinia Radio Telescope
• A perfect power-law spectrum even at highest frequencies: The Toothbrush relic
• Downstream depolarization in the Sausage relic: a 1-4 GHz Very Large Array study
• Limiting the shock acceleration of cosmic-ray protons in the ICM
• Characterizing the Uncertainty in Cluster Magnetic Fields derived from Rotation Measures
• Morphology of radio relics II: Properties of polarised emission
• Spectro-polarimetric observations of the CIZA J2242.8+5301 northern radio relic: no evidence of high-frequency steepening

Cited by in corpus (14)

• Intracluster magnetic filaments and an encounter with a radio jet
• Deep low-frequency radio observations of Abell 2256 I: The filamentary radio relic
• The detection of cluster magnetic fields via radio source depolarisation
• LOFAR high-band antenna observations of the Perseus cluster
• Deep low-frequency radio observations of Abell 2256 II: The ultra-steep spectrum radio halo
• Particle re-acceleration and diffuse radio sources in the galaxy cluster Abell 1550
• Probing the Timescale of the 1.4 GHz Radio emissions as a Star formation tracer
• Using the polarization properties of double radio relics to probe the turbulent compression scenario
• The diffuse radio emission in the high-redshift cluster PSZ2 G091.83+26.11: total intensity and polarisation analysis with Very Large Array 1-4 GHz observations
• A formation mechanism for "Wrong Way" Radio Relics
• A new enigmatic radio relic in the low mass cluster Abell 2108
• Unveiling The Origin of Peculiar Diffuse Radio Emission in Abell 1351
• A 600 kpc complex radio source at the center of Abell 3718 discovered by the EMU and POSSUM surveys
• Relighting the fire in Hickson Compact Group (HCG) 15: magnetised fossil plasma revealed by the SKA Pathfinders & Precursors