Sulfur-bearing Molecules in Orion KL

Abstract

We present an observational study of the sulfur (S)-bearing species towards 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 6 S-bearing species. In these S-bearing species, we found a clear dichotomy between carbon-sulfur compounds and carbonfree S-bearing species in various characteristics, e.g., line profiles, spatial morphology, and molecular abundances with respect to H 2 . Lines from the carbon-sulfur compounds (i.e., OCS, 13 CS, 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, H 2 S) are spatially more extended to the northeast of mm4, exhibiting broader FWHM linewidths (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 K 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.

Evidence for dense gas heated by the explosion in Orion KL

“…The morphology of para-H 2 CS 7-6 emission in the Orion KL region is similar to results previously obtained with other molecular tracers, e.g., NH 3 , H 2 CO, CH 3 OH, CH 3 CN, HCOOCH 3 , HC 3 N, and SO 2 (e.g., Wilson et al 2000;de Vicente et al 2002;Wang et al 2010;Favre et al 2011;Goddi et al 2011;Gong et al 2015;Peng et al 2017;Luo et al 2019;Pagani et al 2019). However, the northwestern clump was not always detected.…”

“…Thioformaldehyde (H 2 CS), like H 2 CO a slightly asymmetric rotor molecule, exhibits a large number of millimeter and submillimeter transitions (e.g., Wootten & Mangum 2009;Tercero et al 2010;Widicus Weaver et al 2017;Luo et al 2019;Brinkmann et al 2020;van't Hoff et al 2020;Johnston et al 2020). It is a sensitive tracer to probe the kinetic temperature, T kin , of dense gas with line ratios involving different K a ladders because the relative populations of the K a ladders of H 2 CS are governed by collisions (Mangum & Wootten 1993;Wootten & Mangum 2009;Oya et al 2016;van't Hoff et al 2020).…”

A search for cloud cores affected by shocked carbon chain chemistry in L1251

“…2) and may be more evolved, since N 2 H + tends to be enhanced in evolved regions (Caselli et al 2002;Liu et al 2019b), while CS J = 2-1 is usually characterized by more extended emission, which is getting closer to the size of the CO emission region (Wu 1993). Besides, the abundance of CS tends to be enhanced in turbulent regions, and CS emission is consistent with the chemical effects expected in shocked regions (Hartquist et al 1980;Zhou et al 1989;Suzuki et al 1992;Luo et al 2019). The depletion of the CS molecule (Vastel et al 2018;Kim et al 2020) in the dense region of F1-M will also make the CS emission look more extended.…”

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP). I. Detection of New Hot Corinos with the ACA

“…Recently, Luo et al (2019) presented opposite temperature dependencies in the abundances of carbon-sulfur compounds (e.g. 13 CS and OCS) and carbon-free sulfur-bearing species (e.g.…”