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Bayesian analysis of cosmic-ray propagation: evidence against homogeneous diffusion

Jóhannesson, G.; Ruiz de Austri, R.; Vincent, A.C.; Moskalenko, I.V.; Orlando, E.; Porter, T.A.; Strong, A.W.; Trotta, R.; Feroz, F.; Graff, P.; Hobson, M.P.

Bayesian analysis of cosmic-ray propagation: evidence against homogeneous diffusion Thumbnail


Authors

G. Jóhannesson

R. Ruiz de Austri

A.C. Vincent

I.V. Moskalenko

E. Orlando

T.A. Porter

A.W. Strong

R. Trotta

F. Feroz

P. Graff

M.P. Hobson



Abstract

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, $\bar{p}$, and He) from the usual light elements (Be, B, C, N, and O). We find that the propagation parameters that best-fit $p,\bar{p}$, and He data are significantly different from those that fit light elements, including the B/C and 10Be/9Be 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

Citation

Jóhannesson, G., Ruiz de Austri, R., Vincent, A., Moskalenko, I., Orlando, E., Porter, T., …Hobson, M. (2016). Bayesian analysis of cosmic-ray propagation: evidence against homogeneous diffusion. Astrophysical Journal, 824(1), Article 16. https://doi.org/10.3847/0004-637x/824/1/16

Journal Article Type Article
Acceptance Date Mar 29, 2016
Online Publication Date Jun 3, 2016
Publication Date Jun 3, 2016
Deposit Date Aug 19, 2016
Publicly Available Date Aug 22, 2016
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 824
Issue 1
Article Number 16
DOI https://doi.org/10.3847/0004-637x/824/1/16
Publisher URL http://iopscience.iop.org/article/10.3847/0004-637X/824/1/16/meta
Related Public URLs https://arxiv.org/abs/1602.02243

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Copyright Statement
© 2016. The American Astronomical Society. All rights reserved.





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