Detection of UIR bands in an isolated local interstellar cirrus cloud
D. Lemke, K. Mattila, K. Lehtinen, R. J. Laureijs, T. Liljestrom, A. Leger, U. Herbstmeier;
AaA, 1998, 331, 742
ABSTRACT:The unidentified infrared (UIR) emission bands at 7.7 and 11.3 mu m have been detected in the emission of an isolated cirrus cloud externally heated
by the typical interstellar radiation field (ISRF) of the solar
neighbourhood.
For the observations we used ISOPHOT, the photometer aboard ISO.
The
detected UIR bands have absolute intensities ~ 1/1000th of the values typically
observed in planetary and reflection nebulae.
The intensity ratio 11.3 to 7.7
mu m is at the higher end of the range observed for reflection nebulae,
planetaries, HII regions, or for the diffuse emission of the inner Galaxy.
An
enhanced emission level is observed also in the bands 6 - 9 mu m and 12 - 14 mu m,
suggesting the presence of the 6.2, 8.6 and 12.7 mu m UIR bands.
At 10 and 16 mu m
continuum emission has been detected which must be due to very small grains.
The
observations presented give further evidence that the UIR features seem to be
ubiquitous throughout the galaxy.
This is in support of the PAHs as carriers of the
features and, moreover, as key agents in transforming the stellar UV into
infrared radiation.
Based on observations made with ISO, an ESA project with
instruments funded by ESA member states (especially the PI countries: France,
Germany, the Netherlands and the United Kingdom) and with the participation of
ISAS and NASA
KEYWORDS: dust, extinction, infrared: ism: lines and bands, galaxy: general
PERSOKEY:cirrus, iso, dust, pah, mir, ,
CODE: lemke98