Issue |
A&A
Volume 436, Number 2, June III 2005
|
|
---|---|---|
Page(s) | 569 - 584 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20041760 | |
Published online | 30 May 2005 |
New results on the massive star-forming region S106 by BEAR spectro-imagery
1
Centre d'Étude Spatiale des Rayonnements, CNRS et Université Paul Sabatier, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France e-mail: Christine.Joblin@cesr.fr
2
Institut d'Astrophysique de Paris, CNRS et Université P. & M. Curie, 98 bis Bd. Arago, 75014 Paris, France e-mail: maillard@iap.fr
Received:
30
July
2004
Accepted:
20
January
2005
As a typical example of interaction of a massive star with its
parent cloud, the close environment of S106 IR in the
star-forming region S106 was observed at high spectral
resolution (~16 km s-1). Integral field spectroscopy with
BEAR, an imaging Fourier Transform Spectrometer (FTS), on a field of
~40´´in diameter, in the H2 1–0 S(1), 2–1 S(1),
Brγ, and [
] lines. From the data
several maps were obtained: intensity, velocity and linewidth in the
Brγ and the H2 1–0 S(1) line, 1–0 S(1)/2–1 S(1) line ratio,
and continuum emission at 2.1 μm. From the latter, about twenty
low-mass stars were detected with photometry in this band, and an
estimate of their mass was made leading to the conclusion that S106 is a site of
formation of mainly sub-solar mass stars. The intensity structure of the
excited molecular gas H2 was found to be clumpy while the velocity is
almost uniformely at
1.5 km s-1 except to
the south where the velocity reaches up to 15 km s-1 in a zone
limited by the long edge of a rectangular hole in the emission. The
H2 line ratio map with values from 1 to 9 implies that
UV-absorption and shocks are participating in the excitation process. A
PDR model with a temperature of 3700 K for S106 IR was used to retrieve
the H2 gas density and temperature. The density was found to vary
between 1 and 3.5
105 cm-3 with corresponding
temperatures between 660 and 1240 K. The study of the linewidth
distribution indicates for most of the gas a supersonic turbulence with
a mean contribution to the observed profiles of ≥6 km s-1. Turbulence is likely to be responsible for the observed clumpy structure of the excited gas. Point-like spots with a linewidth
as high as 30 km s-1 in one position are detected, which may be
vortices in the molecular gas.
The
region probed by Brγ shows a broad range of velocity, from -45 to +80 km s-1, organized in velocity structures that correspond
to two pairs of large, bipolar outflows originating from the massive
source, not directed along the axis of the
region. Emission
lines of
and [
] are detected in a bright area
to the southwest of S106 IR, with point-like structures suggesting
photoevaporating clumps. From the velocity data, a 3-D model of the
environment of S106 IR is proposed. S106 is an example of an evolved
region seen face-on. The central source located at the edge
of its parent molecular cloud has carved an expanding cylinder of
turbulent, atomic gas of
0.1 pc in radius. This massive object
was formed by an accretion disk process. The disk is still present and
the bipolar outflows are remnants of the massive star activity. A time
scale of 1400 yr is estimated for the most recent event. A thin and
quiescent clumpy layer of warm H2 marks the transition of the
region to the molecular cloud. From the data, there are
locally no signs of ongoing star formation.
Key words: stars: formation / ISM: individual objects: Sh 2-106 / instrumentation: interferometers / HII regions / astrochemistry
© ESO, 2005
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