The following document lists the file abstract/JSTUTZKI_PDRDENS.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
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.