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Cosmic Ray Transport and Calorimetry in the Simulated LMC

Published onJun 01, 2020
Cosmic Ray Transport and Calorimetry in the Simulated LMC

Supernova-driven outflows are an important component of stellar feedback in dwarf galaxies, and cosmic-rays produced by supernovae are a promising driver of outflows. The Large Magellanic Cloud (LMC), a well-studied satellite galaxy of the Milky Way, may harbor such a cosmic-ray driven outflow, making it a great test subject to learn more about cosmic-rays and their influence on galaxies. In this project, we compare the known, diffuse gamma-ray luminosity of the LMC to predictions from FLASH magnetohydrodynamic (MHD) simulations, in order to test different cosmic ray transport models. Specifically, gamma-ray studies inform us that cosmic-rays in the LMC only lose ~1% of their energy to hadronic collisions, which is far below expectations from state-of-the-art simulations. This discrepancy may be resolved, however, by including physically-motivated, faster cosmic ray transport through multiphase gas, thereby decreasing hadronic collisions in the interstellar medium. I’ll show synthetic gamma-ray emission maps and total gamma-ray luminosity for a set of LMC-specific outflow simulations. These simulations, building on the work of Bustard et al. 2020, include cosmic-ray production at supernovae and star formation motivated by the inferred star formation history of the LMC. New simulations take into account super-Alfvenic cosmic-ray streaming in partially neutral gas. We vary the factor by which the streaming velocity is boosted compared to the Alfven velocity and explore changes in gamma-ray production in each case.

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