TMGS star positions

The sources were selected from the TMGS to have a K magnitude brighter than +5mag and to be within 2deg of the Galactic plane. More than 60% of the spectra correspond to stars of luminosity class I, and a significant proportion of the remainder are very late and fast-evolving giants.

This very high concentration of young sources points to the existence of a major star formation region in the Galactic plane, located just inside the assumed origin of the Scutum spiral arm. Such regions can form because of the concentrations of shocked gas where a galactic bar meets a spiral arm, as is observed at the ends of the bars of face-on external galaxies. Thus, the presence of a massive star formation region is very strong supporting evidence for the presence of a bar in our Galaxy.