Multi-messenger aspects: Composition, propagation, & acceleration

Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland

^a e-mail: taylora@cp.dias.ie

Published online: 3 August 2015

Abstract

Using recent Pierre Auger Observatory results on the UHECR spectrum and composition, the requirements placed on the sources of these particles are discussed. In this sense, the author interprets the term “multi-messenger” throughout as to refer to the additional information provided by the composition. The spatial distribution of these sources is investigated along with the energy distribution of UHECR they output. These investigations reveal the need for local UHECR sources which output a hard spectrum of intermediate/heavy UHECR. These results demand that local (<80 Mpc) UHECR sources exist, placing exciting and difficult requirements on the local extragalactic candidate sources. Angular correlation studies in collaboration with composition information also demonstrated to offer great potential for isolating the UHECR source distance for which an angular clustering of events is found. Specifically, for the case a correlation of the 13 events correlated with the direction of Cen A, it is shown that the composition information, and specifically, the lack of a lower energy proton correlation, can potentially constrain the source distance to be less than 15 Mpc. The fragility of nuclei with accelerators are also used to place constraints are on the source environment. These constraints motivate 0.1–1000 mG strength magnetic fields exist within the source and that quasi-relativistic scatterers are also present. A specific example of a diffuse large scale “nuclei friendly” accelerator, which meets the outline constraints is put forward.