Year: 2026
Type: preprint
Abstract: Major mergers are transformative events in galaxy evolution, dynamically reshaping the stellar and gas makeup of the hosts, as well as the galaxy-scale magnetic fields (B-fields) that permeate their interstellar medium (ISM), altering both B-field strength and configuration. In this work, we study in detail the link between the co-evolving gas and B-fields in the cold ISM phase of the nearby Antennae galaxy merger (NGC 4038/4039), using CO(3-2) data from the LAsMA receiver at the APEX telescope and ALMA, together with archival 154 $μ$m dust polarization data from the SOFIA/HAWC+. We characterize trends between measurements of molecular gas intensity and velocity dispersion with polarization measurements at kpc-scales with the APEX and SOFIA data. We find anti-correlations with CO intensity ($ρ\lesssim-0.6$) and CO velocity dispersion ($ρ\lesssim-0.4$), which are signposts of geometric depolarization. Since dust polarization measurements are a density-weighted line-of-sight integrated average of B-field vectors below the beam size, the ALMA data can serve as a proxy of density structures below the SOFIA beam on a channel-by-channel basis. Through a geometric analysis of structures in the ALMA channels, we identify salient kinematic features in the overlap region strongly aligned with the SOFIA-inferred B-field orientation. This indicates that these kinematic features might dominantly lend their orientation to the measured field direction, assuming a correspondence between molecular gas structures and galactic B-fields, owing to their density or high polarization fraction. We also identify a modest trend ($ρ\sim0.5$) between the coherence of the molecular gas, a proxy of the line-of-sight angular dispersion, at small scales, and the SOFIA polarization fraction, showing that the polarization fraction measured at $\sim2$ kpc scales is sensitive to structures at $\sim50$ pc scales.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, University of South Carolina, National Radio Astronomy Observatory, Universities Space Research Association, European Commission, Korea Astronomy and Space Science Institute, Universitetet i Oslo, National Astronomical Observatory of Japan, Universität Stuttgart, National Science and Technology Council, HORIZON EUROPE Framework Programme, Research Executive Agency, National Institutes of Natural Sciences
OpenAlex ID: W7220382299