Simulating the Galactic multi-messenger emissions with HERMES

Abstract

Context. The study of nonthermal processes such as synchrotron emission, inverse Compton scattering, bremsstrahlung, and pion production is crucial to understanding the properties of the Galactic cosmic-ray population, to shed light on their origin and confinement mechanisms, and to assess the significance of exotic signals possibly associated to new physics. Aims. We present a public code called HERMES which is designed generate sky maps associated to a variety of multi-messenger and multi-wavelength radiative processes, spanning from the radio domain all the way up to high-energy gamma-ray and neutrino production. Methods. We describe the physical processes under consideration, the code concept and structure, and the user interface, with particular focus on the python-based interactive mode. In particular, present the modular and flexible design that allows the user to easily extend the numerical package according to their needs. Results. In order to demonstrate the capabilities of the code, we describe the details of a comprehensive set of sky maps and spectra associated to all physical processes included in the code. We comment in particular on the radio, gamma-ray, and neutrino maps, and mention the possibility of studying signals stemming from dark matter annihilation. Conclusions. HERMES can be successfully applied to constrain the properties of the Galactic cosmic-ray population, improve our understanding of the diffuse Galactic radio, gamma-ray, and neutrino emission, and search for signals associated to particle dark matter annihilation or decay.

Prospects for detection of a galactic diffuse neutrino flux

“…We use the recently released HERMES code (Dundovic et al, 2021) to convolve along the line of sight the CR spatial and energy distributions modeled with DRAGON2, updated gas (for the hadron emission) and ISRF (for the IC emission) models and the proper γ-ray cross-sections to get detailed full-sky maps of the expected diffuse emissions for each channel.…”

“…Well known examples of these packages are the GALPROP code (Strong and Moskalenko, 1998) which was extensively used by the Fermi-LAT collaboration or the more recently developed PICARD code (Kissmann, 2014). In this work we use the DRAGON2 code (Evoli et al, 2017(Evoli et al, , 2018-to model CR transport-in combination with the recently released HERMES (Dundovic et al, 2021)-to produce simulated spectra and maps of the γ and ν diffuse emissions.…”

Gamma Rays and Neutrinos from the Galactic Plane at the PeV frontier

“…We compute the full-sky maps of the γ-ray diffuse emission as well as the corresponding neutrino emission with the HERMES code [9] feeding it with the CR galactic populations simulated with DRAGON 2 [7,8] for the models discussed in the above.…”

“…2. The absorption due to γ −γ scattering is accounted as described in [9,23]. Its effect is practically negligible below the 100 TeV while just above that energy it is around 10%.…”

“…In this contribution we will present the results obtained with the DRAGON2 numerical code [7,8] -to model CR transport -in combination with the recently released HERMES [9] -to produce simulated spectra and maps of the γ and ν diffuse emissions. DRAGON2 is built to model CR transport under very general conditions.…”