# Dense Cores, Filaments and Outflows in the S255IR Region of High Mass Star Formation

**Authors:** Igor I. Zinchenko, Sheng-Yuan Liu, Yu-Nung Su, Kuo-Song Wang, Yuan Wang  
**arXiv:** [1911.11447](https://arxiv.org/abs/1911.11447)  
**Date:** 2019-11-26  
**Summary page:** https://www.summarizepaper.com/en/paper/1911.11447v1/

## Key points

- Study conducted by Igor I. Zinchenko and colleagues on S255IR high mass star-forming region
- Intricate spatial and kinematic structures revealed through ALMA observations in Band 7
- Presence of narrow, dense, and warm filamentary structures forming dense walls surrounding high-velocity molecular outflows
- Wide-angle outflow from S255IR-SMA1 core enclosing a narrow jet with shocks detected at ends through SiO(8-7) emission
- Collimated and extended high-velocity outflow originating from core SMA2 displaying periodic ejections possibly linked to binary systems
- Evidence of rotation within parent cores uncovered through C$^{34}$S emission data analysis

## Summary

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In this study, conducted by Igor I. Zinchenko and colleagues, the S255IR high mass star-forming region was investigated at a high angular resolution using ALMA in Band 7. The observations revealed intricate spatial and kinematic structures within the region, including the presence of very narrow (approximately 1000 AU), dense (with densities around $10^7$ cm$^{-3}$), and warm filamentary structures. These structures were found to form dense walls surrounding high-velocity molecular outflows emanating from cores such as S255IR-SMA1 and SMA2. In this comprehensive investigation, the S255IR region is studied to gain insights into the complex dynamics and morphology involved in high-mass star formation. The study focuses on the S255IR region, revealing intricate spatial and kinematic structures through ALMA observations. High angular resolution ALMA observations in Band 7 provide valuable insights into the complex dynamics and morphology present in the S255IR region. The wide-angle outflow from the S255IR-SMA1 core, associated with the NIRS3 young stellar object, was observed to enclose a narrow jet, with shocks detected at the ends of the molecular outflow through SiO(8-7) emission. The SiO abundance in these regions was significantly enhanced, indicating active processes within the outflows. Intricate spatial and kinematic structures are revealed within the S255IR region through ALMA observations, including high-velocity molecular outflows emanating from cores such as S255IR-SMA1 and SMA2. Additionally, a collimated and extended high-velocity outflow was identified originating from core SMA2, displaying a bent structure consisting of knots suggestive of periodic ejections possibly linked to binary systems involving low or intermediate mass protostars. Furthermore, evidence of rotation within parent cores was uncovered through C$^{34}$S emission data analysis. The study provides valuable insights into potential protostellar evolution scenarios within the S255IR region, including evidence of rotation within parent cores and the presence of low-mass compact cores undergoing early stages of star formation. Overall, this comprehensive investigation sheds light on the complex dynamics and morphology present in the S255IR region of high-mass star formation, providing valuable insights into accretion processes, outflow mechanisms, and potential protostellar evolution scenarios within this intriguing astronomical environment.