# The Use Case of a New ISRF on Diffuse Gamma-ray Emission Models

## TL;DR

This paper introduces a new ISRF model within the PICARD code to improve predictions of Galactic diffuse gamma-ray emission, focusing on the GeV to TeV energy range and implications for H.E.S.S. observations.

## Contribution

It develops and integrates a new ISRF model into the PICARD code, enhancing the accuracy of gamma-ray emission predictions in the Galaxy.

## Key findings

- Differences in ISRF models significantly affect gamma-ray emission predictions.
- New model provides more robust predictions for very high energy gamma-ray signatures.
- Preliminary maps show improved alignment with observational data.

## Abstract

An important contribution to the gamma-ray emission of our Galaxy is the Galactic Diffuse emission. We present specific developments within the PICARD code for modeling of Galactic cosmic ray propagation that are relevant for the computation of the gamma-ray emission to accommodate a new Interstellar Radiation Field (ISRF) model. We study the differences of the individual ISRF models on Galactic Diffuse gamma-ray emission predictions in the GeV to the TeV energy regime. Emphasis was laid on obtaining robust predictions for observable signatures in the very high energy gamma-ray regime with a special attention to the energy regime for H.E.S.S. Preliminary longitude-latitude profile and residuum maps of inverse Compton emissions are shown for axisymmetric and four-arm spiral Galaxy models.