Contributed Talk - Splinter ISM

Wednesday, 23 September 2020, 17:23   (virtual room F)

Polarization mapping of B335 and L483: magnetic fields and dust evolution from cloud to core scales

Fabio P. Santos
Max Planck Institute For Astronomy

Interstellar magnetic fields are believed to play an important role in regulating the cloud-core gravitational collapse that leads to star formation. However, the differences in magnetic field structure and grain properties from cloud-core scale down to the scale of the protostellar disk are poorly understood. Using new optical and near-infrared polarization data toward two well-known Class 0/I sources (B335 and L483), we investigate how the cloud-scale magnetic field morphology is affected by the bipolar outflows, and how it connects with the inner portions near the forming protoplanetary disk. For B335, this is made possible by comparing with ALMA polarization data and MHD simulations. The magnetic field direction was compared to the bipolar outflow orientation of B335 and L483. For B335, we employ polarization spectrum Serkowski curve fits to estimate the lambda_max parameter, which represents the wavelength at which the spectrum reaches its peak polarization degree value. For both sources, the bipolar outflow orientation is strongly correlated with the magnetic field direction up to the ~0.15 pc scale, which covers the full length of the CO emission that traces de outflow. B335 shows a smooth increase in lambda_max from the cloud outskirts into the inner core portions. After discarding possible grain alignment effects, this result is interpreted as due to grain growth correlated to the increased density near the core center. This provides a connection with a recently published indirect evidence of large grains near the B335 protostellar disk, as revealed from analysis of the ALMA data. The bipolar outflows in B335 and L483 likely dominate the energetics over the magnetic field, up to the entire length of the outflow itself. The presence of larger grains near the B335 protostellar disk, as evidenced from ALMA data, is likely a result from a smooth grain growth process that begins in the outskirts of the star forming core.