TY  - JOUR
A1  - Liu, Ruo-Yu
A1  - Yan, Huirong
A1  - Wang, Xiang-Yu
A1  - Shao, Shi
A1  - Li, Hui
T1  - Gamma-Ray production in the extended halo of the galaxy and possible implications for the origin of galactic cosmic rays
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Various studies have implied the existence of a gaseous halo around the Galaxy extending out to similar to 100 kpc. Galactic cosmic rays (CRs) that propagate to the halo, either by diffusion or by convection with the possibly existing large-scale Galactic wind, can interact with the gas therein and produce gamma-rays via proton-proton collision. We calculate the CR distribution in the halo and the gamma-ray flux, and explore the dependence of the result on model parameters such as diffusion coefficient, CR luminosity, and CR spectral index. We find that the current measurement of isotropic gamma-ray background (IGRB) at less than or similar to TeV with the Fermi Large Area Telescope already approaches a level that can provide interesting constraints on the properties of Galactic CR (e.g., with CR luminosity L-CR <= 1041 erg s(-1)). We also discuss the possibilities of the Fermi bubble and IceCube neutrinos originating from the proton-proton collision between CRs and gas in the halo, as well as the implication of our results for the baryon budget of the hot circumgalactic medium of our Galaxy. Given that the isotropic gamma-ray background is likely to be dominated by unresolved extragalactic sources, future telescopes may extract more individual sources from the IGRB, and hence put even more stringent restrictions on the relevant quantities (such as Galactic CR luminosity and baryon budget in the halo) in the presence of a turbulent halo that we consider.
KW  - cosmic rays
KW  - Galaxy: halo
KW  - gamma rays: diffuse background
KW  - neutrinos
Y1  - 2019
U6  - https://doi.org/10.3847/1538-4357/aaf567
SN  - 0004-637X
SN  - 1538-4357
VL  - 871
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -