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These Herschel data are complemented by unpublished observations by the Infrared Space Observatory Long Wavelength Spectrometer ( ISO LWS ) , which used parallel mode scans to obtain photometric images of the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 \mu m , where the emission peaks .
We also include data from the Midcourse Space Experiment ( MSX ) at 21.3 \mu m for completeness .
We model the combined ISO LWS continuum plus Herschel PACS and SPIRE photometric data toward the central 2 pc in Sagittarius A ^ { * } ( SgrA ^ { * } ) , 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 grey-body 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 \sim 5.0 \times 10 ^ { 4 } \mbox { M } _ { \odot } , with luminosities : L _ { cavity } \sim 2.2 \times 10 ^ { 6 } L _ { \odot } and L _ { CND } \sim 1.5 \times 10 ^ { 6 } L _ { \odot } 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 \sim 3.2 \times 10 ^ { 4 } \mbox { M } _ { \odot } ; 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 .