Issue |
A&A
Volume 472, Number 2, September III 2007
|
|
---|---|---|
Page(s) | 471 - 482 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20066374 | |
Published online | 25 May 2007 |
Integral-field spectroscopy of the Galactic cluster [DBS2003]8 *,**
Discovery of an ultra-compact HII region and its ionizing star in the bright rimmed cloud SFO49
1
European Southern Observatory, Karl Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany e-mail: mmessine@eso.org; messineo@cis.rit.edu
2
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53 121 Bonn, Germany
3
Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
Received:
10
September
2006
Accepted:
23
April
2007
Context.We have started a program of infrared (IR) studies of the stellar clusters associated with HII regions in order to understand the structure of the spiral arms and their interaction with the central bar of the Galaxy better.
Aims.This is accomplished by determining the distance to the OB stars embedded in the clusters. We want to use IR stellar spectro-photometric measurements to complement the kinematic distances from the radial velocity of the gas.
Methods.SINFONI, the infrared integral-field spectrograph of the VLT, enabled us to image the clusters and to resolve them into individual stars, to get the spectra of the brightest stars, and to analyze the possible nebular emission. We performed pilot observations of [DBS2003]8, an embedded Galactic stellar cluster in the bright rimmed cloud SFO49, during the SINFONI science verification. The results are presented in this paper.
Results.The center of the cluster is resolved for the first time and four
stars are detected, the brightest being a late O type or early B star.
A spectro-photometric distance to the cluster of
kpc is derived. We discovered that the O type star is
located in the center of a nebula, which is quite circular in shape
with an observed radius of ~0.03-0.06 pc, a value typical
of an ultra-compact HII region. We measured the nebula's
emission, which is generated by photo-ionization of the
central star; and from the hydrogen molecular line ratio, we have proved
that the ionized nebula is surrounded by a photo-dissociated region
(PDR). We also detected [FeII] line emission at 1.664 μm. The ratio
of the iron flux to that of the
line is found 15 times higher than in a classical HII region. This suggests that
at least part of the [FeII] line emission emanates from shocked
stellar wind material.
Key words: stars: early-type / ISM: HII regions / Galaxy: structure / infrared: ISM / infrared: stars
© ESO, 2007
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