The Perseus ALMA Chemistry Survey (PEACHES). II. Sulfur-bearing Species and Dust Polarization Revealing Shocked Regions in Protostars in the Perseus Molecular Cloud

Abstract

In protostellar cores, sulfur species are effective probes for the energetic environments, such as shocked regions. With the majority of sulfur depleted on dust grains, sulfur-bearing molecules could be liberated back to gas phase by shocks associated with accretion and outflow activities. Therefore, the gas-phase abundance of these molecules may be correlated to the change of dust properties, which can be investigated through polarization observations. Here we present a comparison study of sulfur species and dust polarization at ∼100 au scale for nine protostars in the Perseus Molecular Cloud. Overall, the emission of sulfur-bearing molecules correlates with the high and disordered polarization in the extended continuum of eight sources, indicating intense physical conditions (e.g., high temperature) and/or change of dust properties within these regions, while no clear correlation is seen for Per-emb-14. For the more evolved sources with clear disk structures (Per-emb-50 and −18), the enhanced SO/SO _2 emission overlaps with the stark contrast of polarization in the shocked regions near the centrifugal barriers. In the six sources with more extended CS and SO emission, such as Per-emb-11 and -5, the polarization enhancement correlates with the outer edge of outflow cavities and other filaments probed by sulfur-bearing molecules, revealing soft shocks along the outflows and envelopes. Such comparison studies could provide additional diagnostics of the physical properties and activities in star-forming processes, especially for the shocked regions.

Keywords

• Star formation
• Astrochemistry
• Interstellar molecules
• Polarimetry
• Protostars