The G305 star-forming complex: a wide-area radio survey of ultra-compact
  HII regions
  We present wide-area radio continuum 5.5 and 8.8 GHz (5.5 and 3.4 cm)
Australia Telescope Compact Array observations of the complex and rich massive
star-forming region G305. The aim of this study is to perform an un-targeted
survey of the region in search of the compact radio emission associated with
ultra-compact (UC) HII regions. Observations presented here encompass the
entire complex and have a maximum resolution of ~1.5x1.4" and sensitivity of
~0.07 mJy beam^-1. By applying a data reduction method that emphasises
small-scale structure, we are able to detect 71 compact radio sources
distributed throughout the observed field. To explore the nature of these
compact radio sources we compare to mid-infrared data and in this way identify
56 background sources, eight stellar radio sources, a single bright-rimmed
cloud and six candidate UCHII regions. The physical properties of these
candidate UCHII regions are determined and reveal five candidates have peak
properties consistent with known UCHII regions with source radii ranging from
0.04-0.1 pc, emission measures from 2.56--10.3x10^-6 pc cm^-6 and electron
densities of 0.34--1.03x10^4 cm^-3. We comment on these sites of recent massive
star formation within G305 and by comparing to other star formation tracers
(masers, NH3, YSOs) build a picture of the star formation history of the
region. Using these results we estimate a lower limit to the star formation
rate for the region of ~0.003 Msun yr^-1.
