We have observed the Class I protostellar source Elias 29 with Atacama Large Millimeter/submillimeter Array (ALMA). We have 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 4arcsec ($sim 500$ au). The former component is found to be abundant in SO and SO$_2$ but deficient in CS. The abundance ratio SO/CS is as high as $3^{+13}_{-2} times 10^2$ 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 the deficiency in organic molecules and richness in SO and SO$_2$ to the evolved nature of the source or the relatively high dust temperature (protectraisebox{-0.7ex}{$:stackrel{textstyle >}{sim}:$} 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 ($i geq 65$degr; 0degr for a face-on configuration) and Keplerian motion for simplicity, the protostellar mass is estimated to be (0.8 -- 1.0) Msun. The $^{34}$SO and SO$_2$ emissions are asymmetric in their spectra; the blue-shifted components are weaker than the red-shifted ones. Although this may be attributed to the asymmetric molecular distribution, other possibilities are also discussed.
تحميل البحث