Article,
Magnetic Fields and Massive Star Formation
Astrophys. J., (Sep 15, 2014)
DOI: 10.1088/0004-637x/792/2/116
Abstract
Massive stars (M > 8 M <SUB>&sun;</SUB>) typically form in
parsec-scale molecular clumps that collapse and fragment, leading to the
birth of a cluster of stellar objects. We investigate the role of
magnetic fields in this process through dust polarization at 870 mum
obtained with the Submillimeter Array (SMA). The SMA observations reveal
polarization at scales of lsim0.1 pc. The polarization pattern in these
objects ranges from ordered hour-glass configurations to more chaotic
distributions. By comparing the SMA data with the single dish data at
parsec scales, we found that magnetic fields at dense core scales are
either aligned within 40° of or perpendicular to the parsec-scale
magnetic fields. This finding indicates that magnetic fields play an
important role during the collapse and fragmentation of massive
molecular clumps and the formation of dense cores. We further compare
magnetic fields in dense cores with the major axis of molecular
outflows. Despite a limited number of outflows, we found that the
outflow axis appears to be randomly oriented with respect to the
magnetic field in the core. This result suggests that at the scale of
accretion disks (lsim 10<SUP>3</SUP> AU), angular momentum and dynamic
interactions possibly due to close binary or multiple systems dominate
over magnetic fields. With this unprecedentedly large sample of massive
clumps, we argue on a statistical basis that magnetic fields play an
important role during the formation of dense cores at spatial scales of
0.01-0.1 pc in the context of massive star and cluster star formation.
