WB89 520: A small isolated high mass star forming region associated with an extremely metal-poor nebula
WB89 520 appears to be a single somewhat extended red source on optical CCD images. But from our infrared imaging observations, an infrared cluster, including 15 infrared detectable objects, in this region is discovered. In this paper, by discussing and analyzing the observational results of near infrared imaging, optical spectra and 12CO molecular line, together with IRAS and NVSS data, we conclude that WB89 520 is an UC HII region with a very young compact stellar cluster. The spectrum of the UC HII region shows that it is an extremely metal-poor nebula, which has the lowest line ratio of [NII]/Hα (~ 1/56) discoverd in the nebulae of our Galaxy until now. Also it is a very small (0.83 pc(NS) × 1.55 pc(EW)) and isolated high mass star forming region in which there is a B0.5 type star exciting the UC HII region. Possibly it is not an on-arm high mass star forming region and is located far beyond the Perseus arm. Its heliodistance (~ 4.29 kpc) is twice as far as that of the Perseus arm , which means the OB stars are forming not only in GMCs of the spiral arms.
Galaxies and their Constituents at the Highest Angular Resolutions
- Pub Date:
- January 2001