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A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays - I. Method and results for the Leaky-Box model

Abstract : Propagation of charged Cosmic Rays in the Galaxy depends on the transport parameters, which number can be large depending on the propagation model under scrutiny. Yet, a standard approach to determine these parameters is a manual scan, leading to an inefficient and incomplete coverage of the parameter space. The awaited results of forthcoming experiments call for a better strategy. We implement a Markov Chain Monte Carlo (MCMC), which is well suited for multi-parameter determination. Its specificities (burn-in length, acceptance, correlation length, etc.) are discussed in the context of cosmic ray physics. Its capabilities and performances are explored on the phenomenologically well understood Leaky Box Model. A trial function based on binary space partitioning proves to be very efficient, allowing a simultaneous determination of up to nine parameters, including transport and source parameters (slope, abundances). The best model includes both a low energy cut-off and reacceleration, which values are compatible with those found in diffusion models. A Kolmogorov spectrum for the diffusion slope is excluded. The marginalised probability density function for delta and alpha (the slope of the source spectra) are delta~0.55-0.60 and alpha~2.14-2.17, depending on the dataset used and the number of free parameters in the fit. All source spectrum parameters (slope and abundances) are positively correlated among themselves and with the reacceleration strength, but are negatively correlated with the other propagation parameters. A forthcoming study will extend the analysis to the more physical diffusion models
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http://hal.in2p3.fr/in2p3-00311541
Contributor : Emmanuelle Vernay <>
Submitted on : Tuesday, August 19, 2008 - 8:37:10 AM
Last modification on : Wednesday, September 16, 2020 - 4:13:48 PM

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A. Putze, L. Derome, D. Maurin, L. Perotto, Richard Taillet. A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays - I. Method and results for the Leaky-Box model. Astronomy and Astrophysics - A&A, EDP Sciences, 2009, 497, pp.991-1007. ⟨10.1051/0004-6361/200810824⟩. ⟨in2p3-00311541⟩

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