INVESTIGADORES
PARON Sergio Ariel
artículos
Título:
A bright-rimmed cloud sculpted by the Hii region Sh2-48
Autor/es:
M. E. ORTEGA, S. PARON, E. GIACANI, M. RUBIO, G. DUBNER
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Lugar: Paris; Año: 2013 vol. 556 p. 1 - 8
ISSN:
0004-6361
Resumen:
Aims: We characterize a bright-rimmed cloud embedded in the H ii
region Sh2-48 while searching for evidence of triggered star formation.
Methods: We carried out observations towards a region of 2'
× 2' centered at RA =
18h22m11.39s, Dec =
-14°35'24.81''(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'' × 5''. The molecular
transitions were used to study the distribution and kinematics of the
molecular gas of the bright-rimmed cloud. The radio continuum data was
used to characterize the ionized gas located on the illuminated border
of this molecular condensation. Combining these observations with
infrared public data allowed us to build up a comprehensive picture of
the current state of star formation within this cloud. Results:
The analysis of our molecular observations reveals a relatively dense
clump with n(H2) ~ 3 × 103cm-3,
located in projection onto the interior of the H ii region Sh2-48. The
emission distribution of the four observed molecular transitions has, at
VLSR ~ 38 km s-1, morphological anticorrelation
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 on the border of the clump that is facing the ionizing star.
The ionized gas has an electron density of about 73 cm-3,
which is a factor three higher than the typical critical density
(nc ~ 25 cm-3), above which an ionized boundary
layer can be formed and maintained. This supports the hypothesis that
the clump is being photoionized by the nearby O9.5V 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 prepressure
balance state with the shocks being driven into the surface layer. Among
the five YSO candidates found in the region, two of them (class I) are
placed slightly beyond the bright rim, suggesting that their formation
could have been triggered by the radiation-driven implosion process.