# Different Evolutionary Stages in the Massive Star Forming Region S255 Complex

**Authors:** Y. Wang, H. Beuther, A. Bik, T. Vasyunina, Z. Jiang, E. Puga, H. Linz, J. A. Rodon, Th. Henning, M. Tamura  
**arXiv:** [1011.3575](https://arxiv.org/abs/1011.3575)  
**Date:** 2010-11-16  
**Summary page:** https://www.summarizepaper.com/en/paper/1011.3575v1/

## Key points

- Researchers studied the S255 Complex, observing three distinct regions (S255IR, S255N, and S255S) at different evolutionary stages within the same natal molecular cloud.
- Utilized observations at 1.3 mm with the SMA and additional data from the IRAM 30m telescope for comprehensive analysis.
- Near infrared H + K-band spectra and continuum observations were obtained for S255IR using VLT-SINFONI to investigate diverse stellar populations.
- Combination of millimeter and near infrared data allowed detailed characterization of various stellar populations within the young forming cluster.
- Multiple mm continuum sources identified in all regions with unique outflow, disk, and chemical properties.
- S255IR displayed a collimated bipolar outflow visible in CO and H2 emission while S255S showcased small confined outflows around mm continuum peaks.
- Significant differences in chemistry observed among regions; advanced evolution with strong emission from complex molecules in S255IR, fewer molecular lines detected in S255N, only CO isotopologues and SO lines identified in S255S.
- Rotational structures observed in both S255N and S255IR.
- Comparison of NIR data from S255IR revealed two distinct (proto) stellar populations with an estimated age difference of approximately 1 million years.
- Findings support a triggered outside-in collapse star formation scenario on a larger scale while suggesting a fragmentation scenario specifically for region S255IR.

## Summary

In the study of the massive star forming region S255 Complex, researchers observed three distinct regions (S255IR, S255N, and S255S) at different evolutionary stages within the same natal molecular cloud. Utilizing observations at 1.3 mm with the Submillimeter Array (SMA) and additional data from the IRAM 30m telescope, the team conducted a comprehensive analysis of these regions. Specifically, near infrared (NIR) H + K-band spectra and continuum observations were obtained for S255IR using VLT-SINFONI to investigate the diverse stellar populations present in this area. The combination of millimeter (mm) and near infrared data allowed for a detailed characterization of various stellar populations within the young forming cluster. Multiple mm continuum sources were identified in all regions, each exhibiting unique outflow, disk, and chemical properties. The most evolved source, S255IR, displayed a collimated bipolar outflow visible in CO and H2 emission. In contrast, the youngest region, S255S, showcased small and confined outflows around the mm continuum peaks. Furthermore, significant differences in chemistry were observed among the regions. S255IR exhibited advanced evolution with strong emission from complex molecules, while fewer molecular lines were detected in S255N. In S255S,, only CO isotopologues and SO lines were identified. Rotational structures were also observed in both S255N and S255IR. A comparison of NIR  from S255IR revealed two distinct (proto) stellar populations with an estimated age difference of approximately 1 million years. Through multi-wavelength spectroscopy and mapping studies, researchers unveiled varying evolutionary phases within the star formation regions. Overall, the findings support a triggered outside-in collapse star formation scenario on a larger scale while suggesting a fragmentation scenario specifically for region S255IR. This comprehensive investigation sheds light on the complex interplay between evolutionary processes and environmental factors shaping  within molecular clouds like those found in the S255 Complex.