Issue |
A&A
Volume 420, Number 2, June III 2004
|
|
---|---|---|
Page(s) | 553 - 569 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20035905 | |
Published online | 28 May 2004 |
New light on the S235A-B star forming region*
1
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
2
Radio Astronomy Laboratory, University of California, Berkeley 601 Campbell Hall, Berkeley, CA 94720, USA
3
IRAM, 300 rue de la Piscine, Domaine Universitaire, 38406 St. Martin d'Hères Cedex, France
4
Joint Astronomy Centre, 660 N. A'ohōkū Place, Hilo, HI 96720, USA
Corresponding author: M. Felli, mfelli@arcetri.astro.it
Received:
19
December
2003
Accepted:
4
March
2004
The S235A-B star forming region has been extensively observed
in the past from the radio to the near IR, but what was happening in the
immediate surroundings of the water maser, placed in between the two
nebulosities, was still unclear because
of insufficient resolution especially in the spectral range
from the Far IR to the mm, even though
there were sound indications that new young stellar objects (YSOs)
are being formed there.
We present here new high resolution maps at mm wavelengths in different
molecules (HCO+, C34S,
H2CS, SO2 and CH3CN), as well as in the 1.2 and 3.3 mm
continuum obtained with the Plateau de Bure interferometer, and
JCMT observations at 450 m and 850
m that
unambiguously reveal the presence of new YSOs placed in between
the two Hii regions S235A and S235B and associated with the water maser.
A molecular core and an unresolved source in the mm and in the sub-mm
are centred on the maser, with indication of mass infall onto the core.
Two molecular bipolar outflows and a
jet originate from the same position. Weak evidence is found for
a molecular rotating disk
perpendicular to the direction of the main bipolar outflow.
The derived parameters indicate that one of the YSOs is an intermediate
luminosity object (
) in a very early evolutionary phase,
embedded in a molecular core of ~
, with a temperature of
30 K. The main source of energy for the YSO could come from
gravitational infall, thus making of this YSO a rare example of intermediate
luminosity protostar representing a link between
the earliest evolutionary phases of massive stars
and low mass protostars of class 0–I.
Key words: stars: formation / ISM: Hii regions / ISM: clouds / radio lines: ISM / infrared: stars
© ESO, 2004
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