On the temperature structure of the Galactic Centre cloud G0.253+0.016
  We present a series of smoothed particle hydrodynamical models of
G0.253+0.016 (also known as 'The Brick'), a very dense molecular cloud that
lies close to the Galactic Centre. We explore how its gas and dust temperatures
react as we vary the strength of both the interstellar radiation field (ISRF)
and the cosmic ray ionisation rate (CRIR). As the physical extent of
G0.253+0.016 along our line-of-sight is unknown, we consider two possibilities:
one in which the longest axis is that measured in the plane of the sky (9.4 pc
in length), and one in which it is along the line of sight, in which case we
take it to be 17 pc. To recover the observed gas and dust temperatures, we find
find that the ISRF must be around 1000 times the solar neighbourhood value, and
the CRIR must be roughly 1E-14 /s, regardless of the geometries studied. For
such high values of the CRIR, we find that cooling in the cloud's interior is
dominated by neutral oxygen, in contrast to standard molecular clouds, which at
the same densities are mainly cooled via CO. Our results suggest that the
conditions near G0.253+0.016 are more extreme than those generally accepted for
the inner 500 pc of the galaxy.
