Sulfur-bearing Molecules in Orion KL

Abstract

We present an observational study of the sulfur (S)-bearing species toward Orion KL at 1.3 mm by combining ALMA and IRAM-30 m single-dish data. At a linear resolution of ∼800 au and a velocity resolution of 1 km s −1 , we have identified 79 molecular lines from six S-bearing species. In these S-bearing species, we found a clear dichotomy between carbon–sulfur compounds and carbon-free S-bearing species for various characteristics, e.g., of line profiles, spatial morphology, and molecular abundances with respect to H 2 . Lines from the carbon–sulfur compounds (i.e., OCS, 13 CS, and H 2 CS) exhibit spatial distributions concentrated around the continuum peaks and extended to the south ridge. The full width at half maximum (FWHM) linewidth of these molecular lines is in the range of 2 ∼11 km s −1 . The molecular abundances of OCS and H 2 CS decrease slightly from the cold (∼68 K) to the hot (∼176 K) regions. In contrast, lines from the carbon-free S-bearing species (i.e., SO 2 , 34 SO, and H 2 S) are spatially more extended to the northeast of mm4, exhibiting broader FWHM line widths (15 ∼ 26 km s −1 ). The molecular abundances of carbon-free S-bearing species increase by over an order of magnitude as the temperature increase from 50 to 100 K. In particular, 34 SO/ 34 SO 2 and OCS/SO 2 are enhanced from the warmer regions (>100 K) to the colder regions (∼50 K). Such enhancements are consistent with the transformation of SO 2 at warmer regions and the influence of shocks.