Secondary Radio and X-Ray Emissions from Galaxy Mergers

Chengchao Yuan, Kohta Murase, Peter Mészáros

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Shocks arising in galaxy mergers could accelerate cosmic-ray (CR) ions to TeV-PeV energies. While propagating in the intergalactic medium, these CRs can produce high-energy neutrinos, electron-positron pairs, and gamma-rays. In the presence of intergalactic magnetic fields, the secondary pairs will radiate observable emissions through synchrotron radiation and inverse Compton scattering. In this paper, we demonstrate that these emissions can explain the radio and X-ray fluxes of merging galaxies such as NGC 660 and NGC 3256. Using our model in combination with the observations, we can constrain the gas mass, shock velocity, magnetic field, and the CR spectral index s of these systems. For NGC 660, a single-zone model with a spectral index 2.1 ≲ s ≲ 2.2 is able to simultaneously reproduce the radio and X-ray observations, while a simple one-zone scenario with s ∼ 2 can describe the radio and a large fraction of X-ray observations of NGC 3256. Our work provides a useful approach for studying the dynamics and physical parameters of galaxy mergers, which can play an important part in future multimessenger studies of similar and related extragalactic sources.

Original languageEnglish (US)
Article number76
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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