The interstellar medium and the massive stellar content toward the SNR
  G18.1-0.1 and neighboring HII regions
  We perform a multiwavelength study toward the SNR G18.1-0.1 and nearby
several HII regions (infrared dust bubbles N21 and N22, and the HII regions
G018.149-00.283 and G18.197-00.181). Our goal is to provide observational
evidence supporting that massive stars usually born in clusters from the same
molecular cloud, which then produce, along their evolution, different
neighboring objects such as HII regions, interstellar bubbles and supernova
remnants. We suggest that the objects analysed in this work belong to a same
complex located at the distance of about 4 kpc. Using molecular data we
inspected the interstellar medium toward this complex and from optical and
X-ray observations we looked for OB-type stars in the region. Analysing public
13CO J=1--0 data we found several molecular structures very likely related to
the HII region/SNR complex. We suggest that the molecular gas is very likely
being swept and shaped by the expansion of the HII regions. From spectroscopic
optical observations obtained with the 2.15 m telescope at CASLEO, Argentina,
we discovered three O-type stars very likely exciting the bubbles N21 and N22,
and an uncatalogued HII region northward bubble N22, respectively. Also we
found four B0-5 stars, one toward the bubble N22 and the others within the HII
region G18.149-0.283. By inspecting the Chandra Source Catalog we found two
point X-ray sources and we suggest that one of them is an early O-type star.
Finally we inspected the large scale interstellar medium around this region. We
discovered a big molecular shell of about 70 pc x 28 pc in which the analysed
complex appears to be located in its southern border.
