A Tomography of the Magnetic Field Structure in IRDC G14.2: Massive Filaments from Large to Small Scales

The process that regulates the formation of massive stars is complex and poorly understood. Such stars are formed deep within dense dusty filaments which fragment, leading to molecular cloud clumps, dense cores, and finally protostars. Theoretical work indicates that magnetic fields play a crucial role in the fragmentation process, but this has never been verified observationally. IRDC G14.2 is one of the best studied massive filamentary systems in the Milky Way, and an ideal laboratory to test theoretical fragmentation studies. The goal of this project is to directly test filament fragmentation theories and combine polarization measurements of IRDC G14.2 from different observatories (SOFIA, SMA, CSO, OPD-LNA) to provide a complete view of the magnetic field structure covering about three orders of magnitude in size scales (from several tens of parsecs to approximately 0.01 pc). Our in-depth study of the magnetic field structure is unparalleled for massive filaments: the widely different wavelengths used by each observatory will effectively allow a tomography of the magnetic field lines, unveiling how it varies along different layers as we go from the cloud's outskirts to its dense cores. SOFIA/HAWC+ observations will provide the fundamental missing connection between the large scales (probed by optical and near-infrared data, OPD-LNA) and the very small scales (probed by upcoming highly ranked SMA polarimetric observations). Previous SMA observations showed a different level of fragmentation between two of the most massive filaments in IRDC G14.2, suggesting different magnetic field strengths. We will calculate the field strength, providing a novel and direct test for theoretical work on massive filament fragmentation. In addition, we will evaluate the energy balance between gravity, magnetic fields and turbulence on different angular scales to identify the dominant energy component for different cloud depths.