Contribution of large polycyclic aromatic molecules to the infrared emission of the interstellar medium
J. L. Puget, A. Leger, F. Boulanger;
AaA, 1985, 142, L19
ABSTRACT:Infrared emission spectra are derived for a population of interstellar graphite grains which have a size distribution similar to that of
polycyclic aromatic molecules of a few angstroms.
The optical properties of the
molecule coronene are used to evaluate the oscillator strength of lattice
vibrations, and an IR spectrum for coronene is calculated which takes into account
the amounts of energy radiated in the far, near, and mid-infrared regions,
respectively.
It is found that the fraction of energy emitted in the mid-infrared is
related to the amount of carbon in the molecules, and may be as large as 10 percent
or more.
On the basis of an analysis of the emission spectra, it is
predicted that the Cirrus Clouds observed by the IRAS satellite at a wavelength of
100 should also be detectable at 12 microns.
It is suggested that the
emission of molecules like coronene is the major source of mid-infrared
radiation in objects on the scale of a galaxy.
A direct test of this suggestion is
the spectroscopic signature which should be present in the emission.
KEYWORDS: emission spectra, graphite, infrared spectra, interstellar extinction, interstellar matter, molecular clouds, evaporation, interstellar radiation, optical properties, particle size distribution
PERSOKEY:dust, ,
CODE: puget85