we propose to investigate the nature of small dust particles in regions of the interstellar medium showing large ir color variations. the observations will consist of one-dimentional rasters (cuts) with isocam accross regions showing high color gradients in the iras data (12 to 100 microns). the selected targets include dense filaments inside cold molecular clouds, edges of molecular clouds in various radiation fields, including some showing enhanced 12 and 25 micron halos, vicinity of hot stars. the cuts will be observed in all ir features attributed to small dust particles (pah, hac, qcc, ..) as well as in the nearby continuum. the origin of the ir color variations is still unknown. the obtained data will therefore constitute a complete data base of small dust particles emission, in regions where their abundance and probably their nature sharply changes with physical conditions as radiation field, density, temperature, .. the proposed observations will provide information on color variations over a wider range of spatial scales and with more specific spectroscopic information. in particular, the combination of filters will allow to separate the continuum and feature emission from small particles.it will be possible to study processes leading to formation and destruction of small dust particles in space, as well as their relationship with the gas phase and dust surface chemistry. possible trigering of small dust particles enhancement by shocks and its impact upon gas phase temperature through photoelectric heating will also be investigated. apart from evidencing abundance variations, these obser- vations may provide information about other properties as size spectrum, dehydrogenation, ionization, .. which affect the ir emission of small particles. this proposal complements the gto program fboulang_smallpar. it is less extenssive as far as sky coverage is concerned, but will give more detailled spectral information, which will be critical to understand the role played by small particles in the ism chemistry.
Instrument
CAM01 , CAM04 , LWS02 , PHT03 , PHT22
Temporal Coverage
1996-08-13T17:10:26Z/1997-07-14T12:43:41Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
