Acerca de
My research aims to understand how cosmic rays propagate through complex astrophysical environments, and how their transport determines where they interact with gas and influence galaxy evolution.
Cosmic-ray transport is often described using an effective diffusion coefficient, but real astrophysical media are structured, turbulent and multiphase. Magnetic geometry, local scattering conditions and gas structure can therefore produce strongly heterogeneous transport, affecting which phases cosmic rays penetrate, where they deposit energy and momentum, and how observable high-energy signatures arise.
I work across scales, from transport microphysics in molecular clouds to cosmic-ray feedback in galaxies and their surrounding environments. My approach combines theoretical and computational modelling with gamma-ray, neutrino, radio and other observational diagnostics.
Cosmic-ray transport in structured environments
Cosmic-ray propagation is often described using a single diffusion coefficient. In reality, astrophysical environments are highly structured: magnetic fields are turbulent and intermittent, gas properties vary strongly between phases, and the scattering conditions encountered by particles can change over very short distances.
My work investigates how this complexity shapes cosmic-ray transport from microscopic to macroscopic scales. In molecular clouds, I use magnetic-field measurements and turbulence statistics to constrain the local scattering environment experienced by cosmic rays, and to determine when transport is diffusive, quasi-ballistic, or intermediate between these limits. A key aim is to understand when a meaningful effective diffusion coefficient can emerge from a heterogeneous medium, and when that approximation breaks down.
More broadly, I study transport processes that depart from simple Brownian diffusion, including stochastic and intermittent propagation through structured magnetic environments. These effects can alter particle confinement, penetration into dense gas, and escape from galaxies and larger-scale structures.
Taurus molecular cloud. Far-infrared observations reveal the filamentary gas structure, while polarisation measurements trace the projected magnetic-field geometry.
Image Credit: ESA/Herschel/SPIRE/PACS/Gould Belt Survey/D. Arzoumanian (CEA Saclay)
Structured magnetic environments produce heterogeneous cosmic-ray transport. Observed variations in magnetic geometry motivate different scattering and propagation regimes across cloud phases.
Adapted from Owen et al. (2021) and Ng, Owen et al. (2026).
Representative work:
-
Multiwavelength Probes of Cosmic Ray Transport in Molecular Cloud Structures (Ng, Owen et al. 2026) [Journal] [arXiv] [ADS]
-
The “Forgotten” Neutrons: Implications for the Propagation of High-Energy Cosmic Rays in Magnetized Astrophysical and Cosmological Structures (Owen et al. 2026) [Journal] [arXiv] [ADS]
-
Observational Signatures of Cosmic-Ray Interactions in Molecular Clouds (Owen et al. 2021) [Journal] [arXiv] [ADS]
Cosmic rays and galaxy evolution
Cosmic-ray propagation is often described using a single diffusion coefficient. In reality, astrophysical environments are highly structured: magnetic fields are turbulent and intermittent, gas properties vary strongly between phases, and the scattering conditions encountered by particles can change over very short distances.
My work investigates this phase-dependent feedback across a range of environments. I have studied how cosmic rays affect starburst-driven outflows, how established CR halos can modify or suppress further wind launching, and how externally supplied CRs interact with cold accretion streams feeding massive galaxies. These results show that the impact of cosmic rays is not set by their total energy alone: it depends strongly on where they propagate and which gas phases they are able to reach.
M82, a nearby starburst galaxy driving a powerful multiphase galactic wind. Outflows redistribute gas, energy and metals between galaxies and their surrounding halos.
Image Credit: X-ray: NASA/CXC/JHU/D.Strickland; Optical: NASA/ESA/STScI/AURA/The Hubble Heritage Team; IR: NASA/JPL-Caltech/Univ. of AZ/C. Engelbracht
A central goal is to connect this transport physics to galaxy-scale models. By identifying how CR coupling changes with gas density, ionisation state, magnetic structure and environment, I aim to develop physically motivated descriptions of CR feedback that can be tested against observations and ultimately incorporated into simulations of galaxy formation.
Representative work:
-
Cosmic Ray Heating of Cold Streams: Implications for the Gas Supply and Growth of Massive Galaxies (Owen et al. 2026) [arXiv] [ADS]
-
Starburst-Driven Galactic Outflows: Unveiling the Suppressive Role of Cosmic Ray Halos (Romano, Owen & Nagamine, 2025) [Journal] [arXiv] [ADS]
-
Cosmic Ray Processes in Galactic Ecosystems (Owen et al. 2023) [Journal] [arXiv] [ADS]
Cosmic-ray halos can change how galactic winds develop. As galaxies build up extended thermal and cosmic-ray halos, the resulting pressure structure can suppress slow CR-driven outflows and promote baryonic recycling.
Adapted from Romano, Owen & Nagamine (2025).
Multimessenger probes of cosmic-ray physics
Cosmic rays cannot usually be traced directly back to their propagation history, but their interactions leave signatures across multiple messengers. Gamma rays, neutrinos, radio emission and ionisation diagnostics each probe different parts of the underlying particle population and different physical environments.
The Milky Way in optical light and high-energy neutrinos. A predicted neutral pion-decay template traces the expected neutrino emission from cosmic-ray interactions with Galactic matter, while IceCube observations reveal diffuse high-energy neutrino emission associated with the Galactic plane.
Adapted from IceCube Collaboration (2023).
My work uses these observables to test how cosmic rays propagate, where they interact, and how efficiently they are confined. I have modelled high-energy emission from molecular clouds, galaxies and galaxy populations, and contributed to studies using neutrinos to probe cosmic-ray interactions in the Galactic Centre. These approaches span resolved Galactic environments to diffuse extragalactic backgrounds, allowing cosmic-ray physics to be tested across very different spatial scales. Combining several messengers is especially powerful because the same underlying transport and interaction physics must remain consistent with multiple observational signatures.
A major aim of this work is therefore to turn cosmic-ray transport from an assumed ingredient into something that can be tested observationally. By comparing predicted gamma-ray, neutrino, radio and ionisation signatures with observations, I aim to identify which transport regimes operate in different environments and where simple diffusive descriptions remain adequate.
Diffuse high-energy backgrounds probe unresolved cosmic-ray populations. Predictions for the gamma-ray contribution of star-forming galaxies vary with assumptions about cosmic-ray transport and galaxy properties, illustrating how background measurements can constrain the underlying physics.
From Owen, Kong & Lee (2022).
Representative work:
-
Neutrinos as a New Tool to Characterize the Milky Way Center (Lai et al. 2026, including Owen) [Journal] [arXiv] [ADS]
-
Multiwavelength Probes of Cosmic Ray Transport in Molecular Cloud Structures (Ng, Owen et al. 2026) [Journal] [arXiv] [ADS]
-
The Extragalactic Gamma-Ray Background: Imprints from the Physical Properties and Evolution of Star-Forming Galaxy Populations (Owen et al. 2022) [Journal] [arXiv] [ADS]
