PT Journal
AU Johannesson, G
   Ruiz de Austri, R
   Vincent, AC
   Moskalenko, IV
   Orlando, E
   Porter, TA
   Strong, AW
   Trotta, R
   Feroz, F
   Graff, P
   Hobson, MP
TI Bayesian analysis of cosmic-ray propagation: evidence against homogeneous diffusion
SO Astrophysical Journal
JI Astrophys. J.
PY 2016
BP 16
EP 19pp
VL 824
IS 1
DI 10.3847/0004-637X/824/1/16
LA English
DE astroparticle physics; cosmic rays; diffusion; Galaxy: general; ISM: general; methods: statistical
AB We present the results of the most complete scan of the parameter space for cosmic ray (CR) injection and propagation. We perform a Bayesian search of the main GALPROP parameters, using the MultiNest nested sampling algorithm, augmented by the BAMBI neural network machine-learning package. This is the first study to separate out low-mass isotopes (p, (p) over bar and He) from the usual light elements (Be, B, C, N, and O). We find that the propagation parameters that best-fit p, (p) over bar, and He data are significantly different from those that fit light elements, including the B/C and Be-10/Be-9 secondary-to-primary ratios normally used to calibrate propagation parameters. This suggests that each set of species is probing a very different interstellar medium, and that the standard approach of calibrating propagation parameters using B/C can lead to incorrect results. We present posterior distributions and best-fit parameters for propagation of both sets of nuclei, as well as for the injection abundances of elements from H to Si. The input GALDEF files with these new parameters will be included in an upcoming public GALPROP update.
ER