The interaction between gas, stellar wind and energetic radiation in star forming regions: “The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M 8)” of F. Damiani published by A&A

Star forming regions are complex environments, shaped by the star formation process (which involves gravity, turbulence and magnetic fields) and the interaction between the clouds and the stellar winds and energetic radiation (X-ray and UV) produced by the newborn stars.

 

The interaction between clouds and stellar wind and radiation is of particular interest. Stellar radiation creates expanding fronts in the parental clouds (called ionization fronts) producing low-density cavities. In simple regions, typically only one cavity forms surrounding the newborn stellar cluster. In more complex regions, more cavities can be produced. The expanding ionization fronts can interact and collide, creating high-density regions in the clouds which can be the site of new star formation events.

 

To analyze these regions numerous high-resolution spectral observations are required in order to resolve the dynamic of the gas. Such data are available now thanks to the Gaia-ESO Survey. More than 50 stellar clusters are in fact included in the survey. Some of these clusters are young and still associated with the parental cloud. To subtract the contribution of the nebula to stellar spectra, several observations of the spectrum of the clouds are taken in positions where no stars are observed (sky spectra): a treasure chest to unveil the properties of the clouds in star forming regions.

 

The study “The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M 8)” of Francesco Damiani (INAF-Astronomical Observatory of Palermo) is focused on the dynamic and morphology of the Lagoon Nebula (M8), the parental cloud of the cluster NGC6530. In this cloud, five cavities are found, one around NGC6530 and four around other massive stars in M8. Some of the expanding fronts of these cavities are colliding. For instance, a high-density cloud is created by the compression due to the expanding shells produced by NGC6530 and the massive star Herchesl36. Besides, for the first time evidence is shown that the even if the cavity around NGC6530 is created the stellar winds produced by the B stars in the cluster, the expanding shell is ionized externally by the massive star 9 Sgr.

 

In the figure (link), a drawing showing the morphology of M8 and its cavities.