High Resolution Radio Observations of Galactic Star Formation
Agnes Scott College
The Very Large Array (VLA) radio interferometer is now equipped with 7
mm detectors on 14 of its 27 radio antennas. While observations at 7 mm
present challenges in terms of phase stability, recent developments in
observing modes and data reduction allow the 7 mm receivers to be placed
at the ends of the array arms, resulting in angular resolution as high
as 0.04". This resolution matches that of the Hubble Space Telescope, and
allows us to probe the detailed structure of star formation regions that
are hidden from optical telescopes. I will present a number of recent
VLA images of star formation regions, in particular Sagittarius B2 and
W49A. High resolution observations of these regions indicate that a number
of the HII regions in these sources are very small (<0.005 pc), and
have high electron densities (n_e~10^6 cm^-3) and emission measures (EM~10^9
pc cm^-6). I will discuss the so-called "lifetime paradox", and explain
how these Ultracompact HII (UCHII) regions may be in pressure equilibrium
with dense local environments.