SiO: Not the perfect outflow tracer: Outflow studies of the massive star
  formation region IRAS 19410+2336
  Aims: Previous observations of the young massive star formation region IRAS
19410+2336 have revealed strong outflow activity with several interacting
outflows. We aim to get a better understanding of the outflow activity in this
region by observing the SiO and H$^{13}$CO$^+$ emission with high angular
resolution. SiO is known to trace shocked gas, which is often associated with
young energetic outflows. With the H$^{13}$CO$^+$ data, we intend to better
understand the distribution of the quiescent gaseous component of the region.
Methods: The SiO observations in the J=2-1 v=0 transition and H$^{13}$CO$^+$
J=1-0 observations were performed by the Plateau de Bure Interferometer,
combined with IRAM 30 m single-dish observations, in order to get the missing
short-spacing information. We complement this new high-resolution observation
with earlier CO and H$_2$ data. Results: The SiO observations do not trace the
previously in CO and H$_2$ identified outflows well. Although we identify
regions of highly increased SiO abundance indicative of shock interaction,
there are hardly any bipolar structures in the data. The southern part of the
region, which exhibits strong H$_2$ emission, shows almost no SiO. The CO and
SiO data show only weak similarities, and the main SiO emission lies between
the two dominating dust clumps of the region. Conclusions: Most SiO emission is
likely to be a result of high-velocity shocks due to protostellar jets.
However, this does not explain all the emission features and additional
effects; for example, colliding gas flows at the interface of the two main
regions may play an important role in the origin of the emission. The present
SiO data show that several different effects can influence SiO emission, which
makes the interpretation of SiO data more difficult than often assumed.
