Dust and Gas environment of the young embedded cluster IRAS 18511+0146
  IRAS 18511+0146 is a young embedded (proto)cluster located at 3.5 kpc
surrounding what appears to be an intermediate mass protostar. In this paper,
we investigate the nature of cluster members (two of which are believed to be
the most massive and luminous) using imaging and spectroscopy in the near and
mid-infrared. The brightest point-like object associated with IRAS 18511+0146
is referred to as S7 in the present work (designated UGPS J185337.88+015030.5
in the UKIRT Galactic Plane survey). Seven of the nine objects show rising
spectral energy distributions (SED) in the near-infrared, with four objects
showing Br-gamma emission. Three members: S7, S10 (also UGPS
J185338.37+015015.3) and S11 (also UGPS J185338.72+015013.5) are bright in
mid-infrared with diffuse emission being detected in the vicinity of S11 in PAH
bands. Silicate absorption is detected towards these three objects, with an
absorption maximum between 9.6 and 9.7 um, large optical depths (1.8-3.2), and
profile widths of 1.6-2.1 um. The silicate profiles of S7 and S10 are similar,
in contrast to S11 (which has the largest width and optical depth). The cold
dust emission investigated using Herschel HiGal peaks at S7, with temperature
at 26 K and column density N(H2) ~ 7 x 10^(22) cm^(-2). The bolometric
luminosity of IRAS 18511 region is L ~ 1.8 x 10^4 L_sun. S7 is the main
contributor to the bolometric luminosity, with L (S7) > 10^4 L_sun. S7 is a
high mass protostellar object with ionised stellar winds, evident from the
correlation between radio and bolometric luminosity as well as the asymmetric
Br-gamma profile. The differences in silicate profiles of S7 and S11 could be
due to different radiation environment as we believe the former to be more
massive and in an earlier phase than the latter.
