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

Abstract

We observed the Class I protostellar source Elias 29 with the Atacama Large Millimeter/submillimeter Array. We detected CS, SO, 34 SO, SO 2 , 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 SO 2 , 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 (HCOOCH 3 , CH 3 OCH 3 , CCH, and c-C 3 H 2 ) are deficient in Elias 29. We attribute this deficiency in organic molecules and richness in SO and SO 2 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 SO 2 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 34 SO and SO 2 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.