| Description |
Herschel SPIRE/PACS photometry observations performed within the HOBYS
(Herschel imaging survey of OB Young Stellar objects) key program have
revealed a wealth of interesting structures in high-mass star forming
regions. The most spectacular of those are pillars and
globules. These features -- partly known from Hubble Space telescope
or Spitzer images -- are formed due to photoevaporation at the
interface between a molecular cloud and an HII region, and are thus
intimately linked to high-mass star formation. The process of how
these pillars are created, and under which conditions low- or
high-mass stars form within them, are not yet clear. Classical
approaches (e.g. Rayleigh-Taylor) can not explain pillar formation, so
we have embarked upon a dedicated project to fully simulate pillars
and globules using the (magneto)-hydrodynamic code HERACLES that
comprises gravity and ionization. The model is intended to be coupled
with a radiative transfer photon dominated region code (KOSMA-tau).
We propose here to make use of the Herschel spectroscopy capacities to
map/make single pointings, in a number of atomic and molecular lines,
of selected pillars and globules in three different regions (Rosette,
Cygnus, M16), spanning a large range in UV intensity and density. We
intend to observe the important cooling lines of CII at 158 micron
and OI at 63 and 145 micron with PACS, the CI finestructure lines
at 370 and 609 micron and the mid-to high-J CO and HCO+ ladder with
the SPIRE FTS. Spectrally resolved CII mapping with HIFI is also
required to derive the velocity information. These observations will
be compared to the large existing complementary data set for each
source, to study the physics of pillars and will additionally serve as
input for the models, to ultimately explain pillar formation and star
formation within them. |
