Abstract:
We present multiwavelength investigation ofmorphology, physical-environment, stellar contents, and star formation
activity in the vicinity of star-forming region Sh 2-100. It is found that the Sh 2-100 region contains seven Hii
regions of ultracompact and compact nature. The present estimation of distance for three Hii regions, along with
the kinematic distance for others, suggests that all of them belong to the same molecular cloud complex. Using
near-infrared photometry, we identified the most probable ionizing sources of six HII regions. Their approximate
photometric spectral type estimates suggest that they are massive early-B to mid-O zero-age-main-sequence stars
and agree well with radio continuum observations at 1280 MHz, for sources whose emissions are optically thin at
this frequency. The morphology of the complex shows a non-uniform distribution of warm and hot dust, well mixed
with the ionized gas, which correlates well with the variation of average visual extinction (~4.2–97 mag) across
the region.We estimated the physical parameters of ionized gas with the help of radio continuum observations.We
detected an optically visible compact nebula located to the south of the 850 μm emission associated with one of the
HII regions and the diagnostic of the optical emission line ratios gives electron density and electron temperature
of ~0.67 × 10³ cm⁻³ and ~10⁴ K, respectively. The physical parameters suggest that all the HII regions are
in different stages of evolution, which correlate well with the probable ages in the range ~0.01–2 Myr of the
ionizing sources. The spatial distribution of infrared excess stars, selected from near-infrared and Infrared Array
Camera color–color diagrams, correlates well with the association of gas and dust. The positions of infrared
excess stars, ultracompact and compact Hii regions at the periphery of an Hi shell, possibly created by a
WR star, indicate that star formation in Sh 2-100 region might have been induced by an expanding Hi shell.
