We report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to 1 arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright "brush" of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range -0.70 ≤ α ≤ -0.80. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below 5 μG and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namely M = 3.78+0.3-0.2. The radio halo shows an average spectral index of α = -1.16 ±0.05 and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightness.
Bibliographical noteFunding Information:
K.R. and M.H. acknowledge support by the research group FOR 1254, funded by the Deutsche Forschungsgemeinschaft: “Magnetization of interstellar and intergalactic media.” Part of this work was performed at Harvard-Smithsonian Center for Astrophysics. R.J.W. is supported by a Clay Fellowship awarded by the Harvard-Smithsonian Center for Astrophysics.
Partial support for L.R. is provided by U.S. National Science Foundation grants 1211595 and 1714205 to the University of Minnesota. F.A.-S. acknowledges support from Chandra grant GO3-14131X. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We thank A. Simionescu for helping with Chandra X-ray analysis. M.J.J. acknowledges support for the current research from the National Research Foundation of Korea under programs 2017R1A2B2004644 and 2017R1A4A1015178.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science