| Description |
We propose to use the The Galactic center (GC) a local extragalactic laboratory to
understand the chemistry and the heating mechanisms in nearby galactic nuclei. The
central 30 pc region around the black hole, Sgr A*, contains all the different type
of activity found in extragalactic nuclei, namely, massive stellar clusters
creating large photodissociation regions (PDR), shocks, molecular clouds irradiated
by strong X-rays (XDRs), and the site of Cosmic Rays (CRs) acceleration as shown by
HESS. We plan to map this region with SPIRE in the high spectral resolution mode and
with HIFI in selected molecular ions H _3 O ^+ , OH ^+ , and H _2 O ^+ claimed to
trace XDRs and/or CRs. This unique data set will provide the possibility to understand
the origin of the large column densities of this hydrides found in galactic nuclei
with different type of activity and the role of the PDR-XDR-CR chemistries in their
formation. The SPIRE data cubes will have a huge legacy value providing the full FIR
inventory of the atomic and molecular gas across the central 50 pc of the Galaxy. We
stress that only the combination of the high spectral resolution of HIFI and the
spatial distribution provided the proposed mapping will have the possibility to
distinguish which of the different components of the molecular gas along the line of
sight correspond to the ones associated with XDRs PDRs and eventually CRs
acceleration sites. |
