The Galactic Centre in the Far Infrared
  We analyse the far infrared dust emission from the Galactic Centre region,
including the Circumnuclear Disk (CND) and other structures, using Herschel
PACS and SPIRE photometric observations. These Herschel data are complemented
by unpublished observations by the Infrared Space Observatory Long Wavelength
Spectrometer (ISO LWS), which used parallel mode scans to obtain photometric
images of the region with a larger beam than Herschel but with a complementary
wavelength coverage and more frequent sampling with ten detectors observing at
ten different wavelengths in the range from 46 to 180 \mum, where the emission
peaks. We also include data from the MSX at 21.3 \mum for completeness. We
model the combined ISO LWS continuum plus Herschel PACS and SPIRE photometric
data toward the central 2 pc in Sgr A*, a region that includes the CND. We find
that the FIR spectral energy distribution is best represented by a continuum
that is the sum of three greybody curves from dust at temperatures of 90, 44.5,
and 23 K. We obtain temperature and molecular hydrogen column density maps of
the region. We estimate the mass of the inner part of the CND to be ~5.0x10e+4
Msum, with luminosities: Lcavity ~2.2x10e+6 Lsun and Lcnd ~1.5x10e+6 Lsun in
the central 2 pc radius around SgrA* . We find from the Herschel and ISO data
that the cold component of the dust dominates the total dust mass, with a
contribution of ~3.2x10E+4 Msun; this important cold material had escaped the
notice of earlier studies that relied on shorter wavelength observations. The
hotter component disagrees with some earlier estimates, but is consistent with
measured gas temperatures and with models that imply shock heating or turbulent
effects are at work. We find that the dust grain sizes apparently change widely
across the region, perhaps in response to the temperature variations, and we
map that distribution.
