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Extended HNCO, SiO, and HC3N Emission in 43 Southern Star-forming Regions
2021-03-25| 【A A A【Print】【Close】

Shocks are a ubiquitous phenomenon in the interstellar medium (ISM) of galaxies. They may be driven by supernova explosions, the pressure of photoionized gas, stellar winds, and collisions between fast-moving clumps of interstellar gas, where the fluiddynamical disturbances proceed at a velocity that exceeds the local sound speed because of the presence of large pressure gradients. The processes of birth, evolution, and death of stars are always associated with shocks. 

Towards a further understanding of shocks in regions of star formation, XAO astronomers Yuxin He, Jianjun Zhou, Jarken Esimbek, and MPIA astronomer Christian Henkel and their colleagues have performed a systematic study of 43 southern star-forming regions in HNCO 404–303, SiO 2–1, and HC3N 10–9, which are good tracers of shocks, based on the MALT90 survey, the 870 μm ATLASGAL survey, and Herschel 160, 250, 350, and 500 μm data. These sources were divided into three groups: those in the Central Molecular Zone (CMZ), those associated with bubbles (Bubble), and the remaining sources, which are termed “normal star-forming regions” (NMSFR). We find that the dust temperature Td, and the abundance ratios NHNCO/NSiO and NHNCO/NHC3N show a decreasing trend toward the central dense regions of CMZ sources, while NHC3N/NSiO moves in the opposite direction. Moreover, a better agreement is found between Td and NHC3N/NSiO in Bubble and NMSFR category sources. Both outflow and inflow activities have been found in eight of the 16 bubble and NMSFR sources. The low outflow detection rate indicates either that in these sources the SiO 2–1 line wing emission is below our sensitivity limit or that the bulk of the SiO emission may be produced by the expansion of an H II region or supernova remnant, which has pushed molecular gas away, forming a shock and yielding SiO. The results have been published in The Astrophysical Journal Supplement (He et al. 2021, ApJS, 253, 2). 

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Figure. Upper panels: contour maps of SiO 2–1, HNCO 404–303, and HC3N 10–9 integrated intensity superimposed on the 870 μm continuum emission map. Lower panels, left to right: contour maps of SiO 2–1 (white solid lines) and HNCO 404–303 (red solid lines) integrated intensity superimposed on the dust temperature map, the extracted beam-averaged spectra of SiO 2–1, HNCO 404–303, and HC3N 10–9 from the position marked by a yellow cross, and normalized variations in NHNCO/NSiO (black line), NHNCO/NHC3N (green line), NHC3N/NSiO (red line) and dust temperature (blue dashed line) along the directions of Galactic longitude and latitude passing through the yellow cross (vertical dashed lines).

Contact: HE Yuxin

Xinjiang Astronomical Observatory, Chinese Academy of Sciences


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