Ultracompact H II Regions with Extended Emission: The Complete View
  In this paper we present the results of a morphological study performed on a
sample of 28 ultracompact \hiirs~located near extended free-free emission,
using radio continuum observations at 3.6~cm with the C and D
VLA~configurations, with the aim of determining a direct connection between
them. By using previously published observations in B and D VLA~configurations,
we compiled a final catalogue of 21 ultracompact \hiirs ~directly connected
with the surrounding extended emission. The observed morphology of most of the
ultracompact \hiirs~in radio continuum emission is irregular (single or
multi-peaked sources) and resembles a classical bubble structure in the
Galactic plane with well-defined cometary arcs. Radio continuum images
superimposed on colour composite \textit{Spitzer} images reinforce the
assignations of direct connection by the spatial coincidence between the
ultracompact components and regions of saturated 24~\micron~emission. We also
find that the presence of extended emission may be crucial to understand the
observed infrared-excess because an underestimation of ionizing Lyman photons
was considered in previous works.
