Abstract:
Three Galactic HII regions, viz., S 201, S 206, and S 209 have
been imaged at three frequencies, viz., 232, 327, and 610 MHz using the GMRT.
The resolutions of these images are typically 15" at 232, 10" at 327, and 6" at
610 MHz. These are the highest resolution low frequency images of these HII
regions. We found that all three HII regions have core-envelope morphologies.
We use the high resolution afforded by the data to estimate the electron
temperatures of the compact cores of these HII regions. These estimates of
the electron temperatures are consistent with an increase in the temperature
with Ga1acto-centric distance; an effect attributed to a decrease in the heavy
elements abundances at large Galacto-centric distances.
