Geometry, Not Calorimetry, Drives the Radio/Infrared/Gamma-Ray Correlation

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Auteurs principaux: Porter, Troy A., Moskalenko, Igor V., Johannesson, Gudlaugur
Format: Preprint
Publié: 2026
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author Porter, Troy A.
Moskalenko, Igor V.
Johannesson, Gudlaugur
author_facet Porter, Troy A.
Moskalenko, Igor V.
Johannesson, Gudlaugur
contents We investigate whether the observed radio-infrared-$γ$-ray correlation in star-forming galaxies is a geometric effect rather than a signature of local cosmic-ray (CR) calorimetry. Using the GALPROP framework, we generate synthetic observations for external viewers from a grid of 3D Milky Way models with varied CR source, gas, interstellar radiation, and magnetic field distributions, all normalised to reproduce local CR data. We find that a tight, quasi-linear correlation arises naturally from line-of-sight integration through the extended, radially-structured disc, even when local calorimetry is absent. The correlation's properties depend strongly on viewing geometry, preserving its form under moderate inclination but breaking down in edge-on views where galactic components are stratified. We conclude that the correlation is primarily an emergent property of geometric projection, not local physics. This implies that its scatter is likely not random noise but a diagnostic of underlying galactic structure and viewing angle.
format Preprint
id arxiv_https___arxiv_org_abs_2604_21224
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Geometry, Not Calorimetry, Drives the Radio/Infrared/Gamma-Ray Correlation
Porter, Troy A.
Moskalenko, Igor V.
Johannesson, Gudlaugur
High Energy Astrophysical Phenomena
Astrophysics of Galaxies
We investigate whether the observed radio-infrared-$γ$-ray correlation in star-forming galaxies is a geometric effect rather than a signature of local cosmic-ray (CR) calorimetry. Using the GALPROP framework, we generate synthetic observations for external viewers from a grid of 3D Milky Way models with varied CR source, gas, interstellar radiation, and magnetic field distributions, all normalised to reproduce local CR data. We find that a tight, quasi-linear correlation arises naturally from line-of-sight integration through the extended, radially-structured disc, even when local calorimetry is absent. The correlation's properties depend strongly on viewing geometry, preserving its form under moderate inclination but breaking down in edge-on views where galactic components are stratified. We conclude that the correlation is primarily an emergent property of geometric projection, not local physics. This implies that its scatter is likely not random noise but a diagnostic of underlying galactic structure and viewing angle.
title Geometry, Not Calorimetry, Drives the Radio/Infrared/Gamma-Ray Correlation
topic High Energy Astrophysical Phenomena
Astrophysics of Galaxies
url https://arxiv.org/abs/2604.21224