Tracing Cloud Formation and Evolution Through 3D Magnetic Field Mapping

TL;DR

The study addresses how magnetic fields influence molecular cloud formation, evolution, and star formation by constructing 3D magnetic field maps. It combines PRIMAger polarization at $92\,\mu\mathrm{m}$ with line-of-sight RM data to derive sub-parsec 3D field vectors for Perseus and Musca, enabling a direct environmental comparison between a bubble-influenced, active cloud and an isolated, quiescent filament. The project outlines explicit integration times and survey design to achieve sub-parsec resolution, providing novel empirical constraints on field–gas coupling and fragmentation that can benchmark magnetohydrodynamic simulations. Multi-wavelength synergies, including radio RM, Zeeman measurements, optical polarimetry with Gaia distances, and CCAT Prime sub-mm polarimetry, will deliver a comprehensive framework for understanding the co-evolution of magnetic fields and molecular clouds across different galactic environments.

Abstract

We propose to use the unprecedented polarization sensitivity of PRIMA's PRIMAger Polarization Imager and its high resolution in Band 1 (92 $μ$m) to map magnetic fields across two contrasting molecular cloud environments: the well-studied Perseus cloud and the isolated Musca filament. This comparative study will leverage the existing VLA radio observations that provide line-of-sight magnetic field component of the Perseus cloud, along with upcoming POSSUM survey results for Musca, to construct the first detailed 3D magnetic field vector maps at sub-parsec resolution. Perseus, with its known formation history through interstellar structure (e.g., bubble) interactions, will reveal how magnetic fields evolve during active star formation phases, while Musca, an isolated filament with lower star-formation activity, will show magnetic field morphology in early evolutionary stages. With PRIMA's resolution of 0.01 pc for Perseus and $<0.01$ pc for Musca, we will resolve magnetic field structures at scales necessary for understanding cloud fragmentation and star formation efficiency, and the roles that magnetic fields play in these processes. Our survey will require approximately 1438 hours to cover 42 deg$^2$ of Perseus and 12 deg$^2$ of Musca. With this, we aim to provide the first comprehensive view of how environment and evolutionary state may influence magnetic field evolution in molecular clouds and how magnetic fields influence cloud formation, fragmentation, and star formation.

Figures (2)

• Figure 1: Left: Perseus cloud's line-of-sight and 3D magnetic fields. Blue/red circles: line-of-sight magnetic fields toward/away from us. Red/drapery lines: Planck-observed plane-of-sky fields. Background: visual extinction map Kainulainenetal2009. Right: Bubbles shaping Perseus (blue contour inside the green circle). Per-Tau (white) and newly-identified structure (green - shape not known) influence cloud. Background: thermal dust emission.
• Figure 2: Herschel (background color) and Planck observations of Musca. The red and drapery lines show the plane-of-sky magnetic fields.