the high brightness of the mid-j 13co, mid-j and high-j 12co lines observed in many uv excited sources require the presence of very high density clumps in pdrs. the presence of these extremely high density clumps within massive star forming regions can be tested unambigiuously through observations of certain pdr species, whose chemical abundance and excitation require high (n(h) < 10^7 cm^-3) or very high densities (n(h) < 10^8 cm-3). such tracers are the h2o, oh and ch rotational lines. theoretical models predict that these molecules are chemically produced very efficiently in the outer hot layers of high density pdrs.
Instrument
LWS01 , LWS04
Temporal Coverage
1996-11-04T18:40:33Z/1997-04-29T07:06:02Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's 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.
