LOFAR, VLA, and Chandra observations of the Toothbrush Galaxy Cluster
Journal Article
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· The Astrophysical Journal (Online)
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- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
- Istituto Nazionale di Astrofisica (INAF), Bologna (Italy)
- Hamburger Sternwarte (Germany)
- Leiden Univ. (Netherlands); Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands); Univ. of Hertfordshire, Hatfield (United Kingdom)
- Leiden Univ. (Netherlands)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Hamburger Sternwarte (Germany); Leiden Univ. (Netherlands)
- Univ. of Hertfordshire, Hatfield (United Kingdom)
- Univ. of Minnesota, Minneapolis, MN (United States)
- Univ. of Edinburgh, Scotland (United Kingdom)
- Univ. of Virginia, Charlottesville, VA (United States)
- Jagiellonian Univ., Krakow (Poland)
- Univ. of Southampton (United Kingdom)
- Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands)
- Max Planck Society, Garching (Germany). Max Planck Inst. for Astrophysics
- Leiden Univ. (Netherlands); National Radio Astronomy Observatory, Socorro, NM (United States)
- Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands); Kapteyn Astronomical Inst., Groningen (Netherlands)
- Thuringer Landessternwarte Tautenburg, (Germany)
- Chalmers Univ. of Technology, Onsala (Sweden)
- Oxford Astrophysics (United Kingdom); Univ. of Western Cape, Bellville (South Africa)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Johns Hopkins Univ., Baltimore, MD (United States)
- Inst. of Space and Astronautical Science, Kanagawa (Japan)
- Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL); The Open Univ., Milton Keynes (United States)
We present deep LOFAR observations between 120 {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 α = -0:8±0:1 at the northern edge of the main radio relic, steepening towards the south to α ≈ -2. The spectral index of the radio halo is remarkably uniform (α = -1:16, with an intrinsic scatter of ≤ 0:04). The observed radio relic spectral index gives a Mach number of M = 2:8+0:5 -0:3, assuming diffusive shock acceleration (DSA). However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock (M≈1:2, with an upper limit ofM≈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.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1430947
- Report Number(s):
- LLNL--JRNL-676706
- Journal Information:
- The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 2 Vol. 818; ISSN 1538-4357
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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