• DOI:10.1051/0004-6361/201322986
• Corpus ID: 54225302

Cosmic ray acceleration and Balmer emission from RCW 86 (G315.4-2.3)

@article{Morlino2013CosmicRA,
  title={Cosmic ray acceleration and Balmer emission from RCW 86 (G315.4-2.3)},
  author={Giovanni Morlino and Pasquale Blasi and R. Bandiera and Elena Amato},
  journal={Astronomy and Astrophysics},
  year={2013},
  volume={562}
}

• G. Morlino, P. Blasi, +1 author E. Amato
• Published 6 November 2013
• Physics
• Astronomy and Astrophysics

INFN/Gran Sasso Science Institute, viale F. Crispi 7, 67100 L’Aquila, ItalyReceived Nov, 2013; accepted –ABSTRACTContext.Observation of Balmer lines from the region around the forward shock of supernova remnants may provide precious infor-mation on the shock dynamics and on the efficiency of particle acceleration at the shock.Aims.We calculate the Balmer line emission and the shape of the broad Balmer line for parameters values suitable for SNR RCW 86(G315.4–2.3), as a function of the cosmic ray (CR) acceleration efficiency and of the level of thermal equilibration between electronsand protons behind the shock. This calculation aims at using the width of the broad Balmer line emission to infer the CR accelerationefficiency in this remnant.Methods. We use the recently developed non-linear theory of diffusive shock acceleration in the presence of neutrals. The semi-analytical approach that we have developed includes a description of magnetic field amplification as due to resonant stre aming insta-bility, the dynamical reaction of both accelerated particles and turbulent magnetic field on the shock, and all channels of interactionbetween neutral hydrogen atoms and background ions that are relevant for the shock dynamics.Results. We derive from Balmer emission the CR acceleration efficiency in the SNR RCW 86. Since our calculation uses recentmeasurements of the shock proper motion, the results depend on the assumed distance to Earth. For a distance of 2 kpc the measuredwidth of the broad Balmer line is compatible with the absence of CR acceleration. For a distance of 2.5 kpc, which is a widely usedvalue in current literature, a CR acceleration efficiency of 5–30% is obtained, depending upon the electron-ion equilibration andthe ionization fraction upstream of the shock. When information on Balmer emission is combined with the measured value of thedownstream electron temperature, the CR acceleration efficiency can be constrained to be ∼ 20%.Key words. acceleration of particles – cosmic rays – Balmer emission – S NR: RCW 86