A deep survey for galactic Wolf-Rayet stars. II. Implications for galactic structure and massive star formation.
SHARA M.M., MOFFAT A.F.J., SMITH L.F., NIEMELA V.S., POTTER M. and LAMONTAGNE R.
Abstract (from CDS):
We have completed a direct narrowband-broadband Schmidt plate survey of large areas of the southern Milky Way for new Wolf-Rayet (W-R) stars as faint as 19th b magnitude. The 31 newly detected stars in the completed survey are among the reddest and/or most distant known in the Galaxy. We have obtained spectra of all candidate W-R stars in the 22 fields stretching from l=282° to l=341° in longitude and Δb=3°.5 in latitude, covering about 180 square degrees. We also observed two isolated Milky Way fields centered at l=0° and l=8°. Eighteen new W-R stars are reported here for the first time. Combined with the 13 new W-R stars we have already reported in Carina, our list of 31 new Galactic W-R stars reaches 3-4 mag fainter than previous surveys. Thirteen of our 18 new W-R stars reported here are of subtype WN, while five are of subtype WC. We present and describe their spectra and subtypes, derive their distances, and discuss the significance of their locations along with all other W-R stars in the Galaxy. Our new W-R stars clearly demonstrate an increasing number ratio of WN to WC stars with increasing Galactocentric distance. We conclude with predictions of the total number of Galactic W-R stars that should be discovered in future IR surveys.