The X-ray Emitting OB Population of MYStIX Star-Forming Regions
Abstract
Despite the large influence of massive stars on their environments, they remain incompletely catalogued. High extinction, diffuse emission, and contamination by foreground and background stars hinder the improvement of the census within massive star forming regions. These difficulties are alleviated by restricting the search to only stars with detectable X-ray emission, and by using infrared photometry. OB stars are distinguished from young stellar objects by fitting the photometry to stellar atmosphere models incorporating extinction. The results are a list of candidate OB stars with inferred extinctions and spectral types, in each of eighteen regions studied in the Massive Young Stellar Complexes in the Infrared and X-ray (MYStIX) project. If correct, these results increase the population of stars of spectral types B1 and earlier by 28% over all the observed regions, with varying percentages of new candidates in each region. Notable results include: the identification of the OB population of a recently discovered third cluster in NGC 6357; the possible identification of a new massive cluster near the Trifid Nebula; the potential identification of some of the influential stars and an increase of 175% of the OB population in NGC 6334; a lack of candidates in the Flame Nebula; a doubling of the OB population in RCW 38, and an increase of 80% in NGC 3576; as well as a number of O candidates, with some potentially as early as O3. Finally, W4 has an overabundance of massive stars for its X-ray emitting population. We also compare to observed spectral types for the candidates in M17 obtained by C. Kobulnicky (private communication), and find that if the proportion holds true for other regions, roughly 67% of the candidates are correctly identified as massive, so that the overall increase of the OB population is 19%.
- Publication:
-
Masters Thesis
- Pub Date:
- 2013
- Bibcode:
- 2013MsT.........19B