Sulfur-bearing Species Tracing the Disk/Envelope System in the Class i Protostellar Source Elias 29

We observed the Class I protostellar source Elias 29 with the Atacama Large Millimeter/submillimeter Array. We detected CS, SO, ³⁴SO, SO₂, and SiO line emissions in a compact component concentrated near the protostar, and a ridge component separated from the protostar by 4″ (∼500 au). The former component is abundant in SO and SO₂, but deficient in CS. The abundance ratio SO/CS is as high as at the protostar, which is even higher than that in the outflow-shocked region of L1157 B1. However, organic molecules (HCOOCH₃, CH₃OCH₃, CCH, and c-C₃H₂) are deficient in Elias 29. We attribute this deficiency in organic molecules and richness in SO and SO₂ to the evolved nature of the source or the relatively high dust temperature (⪆20 K) in the parent cloud of Elias 29. The SO and SO₂ emissions trace rotation around the protostar. Assuming a highly inclined configuration (i ≥ 65°; 0° for a face-on configuration) and Keplerian motion for simplicity, the protostellar mass is estimated to be (0.8-1.0) . The ³⁴SO and SO₂ emissions are asymmetric in their spectra; the blueshifted components are weaker than the redshifted ones. Although this may be attributed to the asymmetric molecular distribution, other possibilities are also discussed.