Constraints on cosmic-ray propagation models from a global Bayesian analysis

TL;DR

This paper develops a Bayesian framework to perform comprehensive parameter estimation for detailed numerical cosmic-ray propagation models, enabling more accurate and statistically robust analysis of cosmic-ray data.

Contribution

It introduces a full Bayesian analysis method for numerical cosmic-ray propagation models using GALPROP, overcoming previous computational challenges.

Findings

Bayesian analysis yields parameter estimates consistent with previous studies.

Demonstrates feasibility of Bayesian methods with computationally intensive models.

Provides a new statistical approach for cosmic-ray propagation modeling.

Abstract

Research in many areas of modern physics such as, e.g., indirect searches for dark matter and particle acceleration in SNR shocks, rely heavily on studies of cosmic rays (CRs) and associated diffuse emissions (radio, microwave, X-rays, gamma rays). While very detailed numerical models of CR propagation exist, a quantitative statistical analysis of such models has been so far hampered by the large computational effort that those models require. Although statistical analyses have been carried out before using semi-analytical models (where the computation is much faster), the evaluation of the results obtained from such models is difficult, as they necessarily suffer from many simplifying assumptions, The main objective of this paper is to present a working method for a full Bayesian parameter estimation for a numerical CR propagation model. For this study, we use the GALPROP code, the most advanced of its kind, that uses astrophysical information, nuclear and particle data as input to self-consistently predict CRs, gamma rays, synchrotron and other observables. We demonstrate that a full Bayesian analysis is possible using nested sampling and Markov Chain Monte Carlo methods (implemented in the SuperBayeS code) despite the heavy computational demands of a numerical propagation code. The best-fit values of parameters found in this analysis are in agreement with previous, significantly simpler, studies also based on GALPROP.