MAGNETIC FIELDS IN HIGH-MASS INFRARED DARK CLOUDS

Abstract

High-mass Stars are cosmic engines known to dominate the energetics in the\nMilky Way and other galaxies. However, their formation is still not well\nunderstood. Massive, cold, dense clouds, often appearing as Infrared Dark\nClouds (IRDCs), are the nurseries of massive stars. No measurements of magnetic\nfields in IRDCs in a state prior to the onset of high-mass star formation\n(HMSF) have previously been available, and prevailing HMSF theories do not\nconsider strong magnetic fields. Here, we report observations of magnetic\nfields in two of the most massive IRDCs in the Milky Way. We show that IRDCs\nG11.11-0.12 and G0.253+0.016 are strongly magnetized and that the strong\nmagnetic field is as important as turbulence and gravity for HMSF. The main\ndense filament in G11.11-0.12 is perpendicular to the magnetic field, while the\nlower density filament merging onto the main filament is parallel to the\nmagnetic field. The implied magnetic field is strong enough to suppress\nfragmentation sufficiently to allow HMSF. Other mechanisms reducing\nfragmentation, such as the entrapment of heating from young stars via high mass\nsurface densities, are not required to facilitate HMSF.\n