Speaker
Description
We present a detailed multi-frequency study of the resolved radio--far-infrared (FIR) correlation in the nearby spiral galaxy IC342 (3.3 Mpc), using new LOFAR 144 MHz observations and archival VLA data at 1.4 and 4.8 GHz, combined with Herschel PACS and WISE infrared maps. After isolating synchrotron emission via thermal/nonthermal separation using $22\mu$ m emission, we analyze spectral indices and derive magnetic field strengths under equipartition. We find synchrotron spectral flattening at low frequencies ($\alpha_{0.14-1.4} = -0.51$ vs. $\alpha_{1.4-4.8} = -1.06$), consistent with aging or low-frequency absorption. Equipartition estimates yield average total fields of $\sim$10~$\mu$G and $B_\text{ord}/B_\text{tur} \sim 0.2$ in star-forming regions. A wavelet-based multiscale correlation analysis reveals a break scale in the radio--FIR correlation at $\sim$200 pc (1.4 GHz) and $\sim$320 pc (144 MHz), interpreted as CRE diffusion lengths. The inferred diffusion coefficient ($D \sim 10^{26}$ cm$^2$ s$^{-1}$) is lower than Galactic averages, implying slower transport or significant escape. We test two CRE propagation models: (i) pure diffusion and (ii) diffusion with escape. The latter yields a tighter match across a sample of galaxies, including IC~342, indicating that turbulent diffusion and vertical escape both shape CRE transport. Moreover, we find a strong positive correlation between diffusion length and ordered magnetic field strength, supporting a contribution from streaming propagation along magnetic field lines. Our results demonstrate that a combination of turbulent diffusion, escape, and possible streaming governs CRE propagation, and must be considered in models linking synchrotron and FIR emission in star-forming galaxies.
