Spectrophotometry of UIR bands in the diffuse emission of the galactic disk.
K. Mattila, D. Lemke, L. K. Haikala, R. J. Laureijs, A. Leger, K. Lehtinen, C. Leinert, P. G. Mezger;
AaA, 1996, 315, L353
ABSTRACT:The spectrum of the unidentified infrared (UIR) emission bands between 5.8 and 11.6{mu}m has been observed for the first time for the diffuse
emission of the galactic disk where the interstellar radiation field (ISRF) is
quite low.
The UIR bands at 6.2, 7.7, 8.6, and 11.3{mu}m have absolute
intensities which are ~1/10th of the values observed in planetary and reflection
nebulae.
However, the intensity ratios and band widths are similar, pointing to a common
carrier for the UIR bands over a large range of different environmental
parameters in the ISM.
This mid-IR emission from a low-ISRF medium and the absence
of any detectable continuum emission at 10{mu}m in the diffuse galactic
spectra go against any significant contribution from grains at equilibrium
temperature or emission during temperature spikes of very small silicate grains;
it supports the identification of the UIR bands as being due to the PAH
molecules.
KEYWORDS: interstellar medium: dust, infrared: ism: bands, galaxy: general
CODE: mattila96