A bright-rimmed cloud sculpted by the H ii region Sh2-48
  To characterize a bright-rimmed cloud embedded in the HII region Sh2-48
searching for evidence of triggered star formation. We carried out observations
towards a region of 2'x2' centered at RA=18h 22m 11.39s, dec.=-14deg 35m 24.81s
(J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in
the 12CO J=3-2,13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular
resolution of about 22". We also present radio continuum observations at 5 GHz
carried out with the Jansky Very Large Array (JVLA; EEUU) interferometer with a
synthetized beam of 7"x5". The analysis of our molecular observations reveals
the presence of a relatively dense clump with n(H_2)~3x10^3 cm^-3, located in
projection onto the interior of the HII region Sh2-48. The emission
distribution of the four observed molecular transitions has, at VLSR~38 kms^-1,
morphological anti-correlation with the bright-rimmed cloud as seen in the
optical emission. From the new radio continuum observations we identify a thin
layer of ionized gas located at the border of the clump which is facing to the
ionizing star. The ionized gas has an electron density of about 73 cm^-3 which
supports the hypothesis that the clump is being photoionized by the nearby
star, BD-14 5014. From the evaluation of the pressure balance between the
ionized and molecular gas, we conclude that the clump would be in a
pre-pressure balance state with the shocks being driven into the surface layer.
Two YSO candidates (class I), are placed slightly beyond the bright rim
suggesting that their formation could have been triggered via the
radiation-driven implosion process.
