The environs of the ultracompact HII region G45.45+0.06
  G45.45+0.06 is an ultra-compact HII (UCHII) region extensively studied. It is
known that G45.45+0.06 is embedded in a complex of UCHII regions, but up the
date, the surrounding ISM in a larger spatial scale has not been analyzed.
Using data from large-scale surveys: Two Micron All Sky Survey, GLIMPSE,
MIPSGAL, MAGPIS and GRS, we performed a multiwavelength study of a region about
7' x 7'in the vicinity of G45.45+0.06. We found that the UCHII complex lies in
a border of a larger (diameter of ~ 3') and fainter HII region, which is
located at the same distance as G45.45+0.06, ~ 8 kpc. In this work, this larger
HII region was called G45L. A good morphological correlation is observed
between the PDRs and the molecular gas mapped in the 13CO J=1--0 and CS J=2--1
lines, suggesting that G45L may be collecting the molecular material. From a
near- and mid-IR photometric study, we found three sources, likely O-type
stars, that are possibly responsible for the creation of G45L. Additionally we
found several YSO candidates lying preferently in the molecular shell that
surrounds G45L. Our results confirm that the region southeastern the UCHII
complex where G45.45+0.06 is embedded and eastern G45L is active in star
formation. We suggest that G45L has been expanding during about 2 x 10^6 yr and
could have triggered the formation of the zero-age main sequence stars that are
ionizing the UCHII region G45.45+0.06. However we can not discard that both HII
regions are coeval.
