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January 01, 2021 article Open access Aachen paper

The Coma Cluster at LOw Frequency ARray Frequencies. I. Insights into Particle Acceleration Mechanisms in the Radio Bridge

The Astrophysical Journal, vol. 907, pp. 32

DOI: 10.3847/1538-4357/abcb8f Full text (OA) OpenAlex

Abstract

Abstract Radio synchrotron emission from the bridges of low-density gas connecting galaxy clusters and groups is a challenge for particle acceleration processes. In this work, we analyze the Coma radio bridge using new LOw Frequency ARray (LOFAR) observations at 144 MHz. LOFAR detects the bridge and its substructures with unprecedented sensitivity and resolution. We found that the radio emission peaks on the NGC 4839 group. Toward the halo, in front of the NGC 4839 group, the radio brightness decreases and streams of radio emission connect the NGC 4839 group to the radio relic. Using X-ray observations, we found that thermal and non-thermal plasma are moderately correlated with a sublinear scaling. We use archival radio data at 326 MHz to constrain the spectral index in the bridge, and quantify the distribution of particles and magnetic field at different frequencies. We found that the spectrum is steeper than −1.4 ± 0.2, and that the emission is clumpier at 326 MHz than at 144 MHz. Using cosmological simulations and a simplified approach to compute particle acceleration, we derive under which conditions turbulent acceleration of mildly relativistic electrons generate the radio emission in the bridge. Assuming that the initial energy ratio of the seed electrons is 3 · 10−4 with respect to the thermal gas, we are able to reproduce the observed luminosity. Our results suggest that the seed electrons released by radio galaxies in the bridge and the turbulence generated by the motion of gas and galaxies are essential to producing the radio emission.

Authors 21

  1. A. Bonafede corresponding

    Universität Hamburg · Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029, Hamburg, Germany

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  2. G. Brunetti

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

    Affiliation as printed

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  3. F. Vazza

    Universität Hamburg · Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029, Hamburg, Germany

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  4. A. Simionescu corresponding Aachen Leiden Observatory SRON Netherlands Institute for Space Research

    Leiden University · Kavli Institute for the Physics and Mathematics of the Universe · Leiden Observatory · Space Research Organisation Netherlands · The University of Tokyo

    Affiliation as printed

    Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583, Japan

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

    SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

  5. G. Giovannini

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  6. E. Bonnassieux

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  7. T. W. Shimwell Aachen Leiden Observatory

    Leiden University · Leiden Observatory · Netherlands Institute for Radio Astronomy

    Affiliation as printed

    ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

  8. M. Brüggen

    Universität Hamburg

    Affiliation as printed

    Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029, Hamburg, Germany

  9. Reinout J. van Weeren Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

  10. A. Botteon corresponding Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

  11. M. Brienza

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  12. R. Cassano

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

    Affiliation as printed

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  13. A. Drabent corresponding

    Thüringer Landessternwarte Tautenburg

    Affiliation as printed

    Thüringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany

  14. L. Feretti

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

    Affiliation as printed

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  15. F. de Gasperin corresponding

    Universität Hamburg

    Affiliation as printed

    Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029, Hamburg, Germany

  16. F. Gastaldello

    National Institute for Astrophysics

    Affiliation as printed

    INAF-IASF Milano, via A. Corti 12, I-20133 Milano, Italy

  17. G. Di Gennaro Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

  18. Mariachiara Rossetti

    National Institute for Astrophysics

    Affiliation as printed

    INAF-IASF Milano, via A. Corti 12, I-20133 Milano, Italy

  19. Huub J. A. Röttgering corresponding Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

  20. C. Stuardi

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics · University of Bologna

    Affiliation as printed

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy; annalisa.bonafede@unibo.it

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    DIFA - Universitá di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

  21. T. Venturi

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

    Affiliation as printed

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy; IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

    INAF - IRA, Via Gobetti 101, I-40129 Bologna, Italy

    IRA-INAF, via P. Gobetti 101, I-40129 Bologna, Italy

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References 65