Momentum deposition of supernovae with cosmic rays

The cataclysmic explosions of massive stars as supernovae are one of the key
ingredients of galaxy formation. However, their evolution is not well
understood in the presence of magnetic fields or cosmic rays (CRs). We study
the expansion of individual supernova remnants (SNRs) using our suite of 3D
hydrodynamical (HD), magnetohydrodynamical (MHD) and CRMHD simulations
generated using RAMSES. We explore multiple ambient densities, magnetic fields
and fractions of supernova energy deposited as CRs ($chi_{rm CR}$),
accounting for cosmic ray anisotropic diffusion and streaming. All our runs
have comparable evolutions until the end of the Sedov-Taylor phase. However,
our CRMHD simulations experience an additional CR pressure-driven snowplough
phase once the CR energy dominates inside the SNR. We present a model for the
final momentum deposited by supernovae that captures this new phase: $p_{rm
SNR} = 2.87times 10^{5} (chi_{text{CR}} +
1)^{4.82}left(frac{n}{text{cm}^{-3}}right)^{-0.196} M_{odot}$ km s$^{-1}$.
Assuming a 10% fraction of SN energy in CRs leads to a 50% boost of the final
momentum, with our model predicting even higher impacts at lower ambient
densities. The anisotropic diffusion of CRs assuming an initially uniform
magnetic field leads to extended gas and cosmic ray outflows escaping from the
supernova poles. We also study a tangled initial configuration of the magnetic
field, resulting instead in a quasi-isotropic diffusion of CRs and earlier
momentum deposition. Finally, synthetic synchrotron observations of our
simulations using the POLARIS code show that the local magnetic field
configuration in the interstellar medium modifies the overall radio emission
morphology and polarisation.
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