Multifrequency Synthesis via CHIBI: Colorful Hierarchical Interferometric Bayesian Imaging

Abstract

From magnetized plasma of relativistic jets to dust grains within protoplanetary disks, we study the emission mechanisms of radio sources via their rich spectral structure. Multifrequency Synthesis (MFS) is a technique in which interferometric data at multiple frequencies are imaged simultaneously, resulting in a denser sampling of spatial scales, higher imaging fidelity, and tighter constraints on the source's spectral structure and evolution. We describe a new method of MFS imaging reconstruction in a hierarchical interferometric Bayesian inference framework, CHIBI. The model parametrization is based on the spectral behavior of synchrotron radiation, the emission mechanism dominating the radio emission observed from galactic nuclei. We show results of this method on observations of jet sources from the MOJAVE catalog with the Very Long Baseline Array, and showcase the prospects for MFS imaging of M87* with simulated data from the Event Horizon Telescope (EHT) and future expansions such as the next generation EHT and the Black Hole Explorer. These demonstrations highlight the benefit of MFS to reconstruct higher-fidelity images and spectral index maps, producing scientifically richer results in a statistically grounded framework, implemented in Comrade.jl.