Ralf Siebenmorgen, Frank Heymann, Endrik Krügel
We present a Monte Carlo (MC) radiative transfer code for complex three
dimensional dust distributions and include transiently heated PAH. The
correctness of the code is confirmed by comparison with benchmark results. The
method makes use of the parallelization capabilities of modern vectorized
computing units like graphic cards. The computational speed grows linearly with
the number of graphical processing units (GPU). On a conventional desktop PC,
our code is up to a factor 100 faster when compared to other MC algorithms. As
an example, we compute the dust emission of proto-planetary disks. We simulate
how a mid-IR instrument mounted at a future 42m ELT will detect such disks. Two
cases are distinguished: a homogeneous disk and a disk with an outward
migrating planet, producing a gap and a spiral density wave. We find that the
resulting mid-IR spectra of both disks are almost identical. However, they can
be distinguished at those wavelengths by coronographic, dual-band imaging.
Finally, the emission of PAHs exposed to different radiation fields is
computed. We demonstrate that PAH emission depends not only on the strength but
also strongly on the hardness of the radiation, a fact which has often been
neglected in previous models. We find that hard photons (>20eV) easily
dissociate all PAHs in the disks of T Tauri stars. To explain the low, but not
negligible detection rate (<10%) of PAHs in T Tau disks, we suggest that
turbulent motions act as a possible path for PAH survival.
View original:
http://arxiv.org/abs/1201.3588
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