A MAJOR STAR-FORMATION REGION IN THE RECEDING TIP OF THE STELLAR GALACTIC BAR

We present an analysis of the optical spectroscopy of 58 stars in the Galactic plane at l = 27 degrees, where a prominent excess in the flux distribution and star counts have been observed in several spectral r egions, in particular in the Two-Micron Galactic Survey (TMGS) catalog . The sources were selected from the TMGS to have a K magnitude bright er than +5 mag and to be within 2 degrees 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-evol ving giants. This very high concentration of young sources points to t he existence of a major star formation region in the Galactic plane, l ocated just inside the assumed origin of the Scutum spiral arm. Such r egions can form because of the concentrations of shocked gas where a g alactic 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 fo rmation region is very strong supporting evidence-for the presence of a bar in our Galaxy.