Small grains and IRAS colors
F. Boulanger, C. Beichman, F. X. Desert, G. Helou, M. Perault, C. Ryter;
ApJ, 1988, 332, 328
ABSTRACT:The paper studies how infrared colors of dust emission from the interstellar medium vary with the energy density of the radiation field on the basis
of IRAS observation of the California Nebula.
The data suggest that
color variations result from a combinatin of equilibrium emission from
large grains, and nonequilibrium emission from small grains, with
destruction of the small grains emitting at 12 microns at high energy density; it is
estimated that 80 percent of these small particles are destroyed for an energy
density in ultraviolet photons larger than 50 times that of the average
interstellar radiation field in the solar neighborhood.
In a color-color diagram,
I(v)(60 microns)/I(v)(100 microns) versus I(v)(12 microns)/I(v)(25
microns), the California Nebula measurements at various distances to the
ionizing star Zeta Per follow a sequence similar to that of galaxies.
This
result shows that the position of a galaxy along this sequence is a measure of
the intensity of the radiation field in the regions responsible for the
infrared emission.
KEYWORDS: color-color diagram, infrared astronomy satellite, infrared sources (astronomy), interstellar matter, reflection nebulae, stellar coronas, cosmic dust, far infrared radiation, radiation distribution, star formation
PERSOKEY:dust, iras, fir, mir, region hii, ,
CODE: boulanger88a