dust heating - photon absorption vs electron collisions
appeared in A&A 556, A6 (2013) DOI: 10.1051/0004-6361/201321054 http://adsabs.harvard.edu/abs/2013A%26A...556A...6B
Dust heating
Photon absorption versus electron collisions
M. Bocchio1, A. P. Jones1, L. Verstraete1, E. M. Xilouris2, E. R.Micelotta3, and S. Bianchi4
1 Institut d’Astrophysique Spatiale (IAS), UMR 8617, CNRS/Université Paris-Sud, 91405 Orsay, France
e-mail: marco.bocchio@ias.u-psud.fr
2 Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens,
P. Penteli, 15236 Athens, Greece
3 Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada
4 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
Received 7 January 2013 / Accepted 18 June 2013
ABSTRACT
Aims. We investigate and quantify the effects of the electron collisional heating of dust
in a hot gas and compare this with photon
heating by the interstellar radiation field.
Methods. We compare the rate of energy absorption by dust due to electron collisional and
photon heating as a function of the physical
conditions of the gas and the ambient radiation field.We calculate the resulting dust
spectral energy distributions (SEDs) for different
environments.
Results. We find that electron collisions and grain charging effects in a hot gas (106?107
K) rapidly destroy small carbonaceous
particles and result in a minimum particle size of the order of a few nm. The charging due
to the emission of secondary electrons
is important and leads to high electric potentials, which quickly destroy the small grains by
field ion emission. In the case of weak
interstellar radiation fields (G0 ? 0.1), electron collisional heating can be the dominant
heating process and therefore makes an
important contribution to the dust thermal emission.
Conclusions. Collisions of electrons with dust grains, in a hot gas, lead to important
changes in the dust SED, as a result of their
high energy input. We find that grain charge effects and accompanying erosion need to be
taken into account in the calculation of the
dust SED. The power absorbed by the dust as a result of electron collisions in a hot tenuous
gas can be larger than that due to photon
absorption in the intergalactic medium close to a galaxy where the radiation field is weak
(G0 <? 0.1).
Key words. dust, extinction – radiation mechanisms: thermal – galaxies: clusters: intracluster medium – radiative transfer –
galaxies: individual: NGC 891