The following document lists the file abstract/TZIMMERM_TZIL1457.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
The closest molecular cloud L1457 represents a unique target to study the interfaces of molecular, atomic, and ionized gas phases at very small size scales; due to its vicinity (65 pc) the highest spatial resolution possible can be achieved. Since molecular clouds show a very inhomogenous spatial structure at all size scales the gas phases are expected to be mixed in high as well as low density regions. We want to determine the ratio of mixing in dependence of the density and the temperature to investigate the physics and chemistry. For this reason we propose to observe strip-like maps in fine-structur transitions of OI and CII along a steep intensity gradient in the southern dense core of L1457 with the ISO LWS. Moreover, observing of the OI 63 mum and the CII 158 mum transitions allow a direct determination of the most important cooling processes of molecular clouds gas which is not possible with ground-based telescopes but only with ISO. Although the CII 158 mum transition has already been detected with COBE in diffuse clouds, the sensitivity and angular resolution obtained with ISO will give a detailed picture of the small scale distribution of CII over an extended region; the same region will be mapped in OI 63 mum, so in addition this would be the first detection of OI in a diffuse cloud. Observing the proposed region, we will manage to cover continuously, with respect to the angular resolution auf ISO, a region containing high as well as low density gas, and determine in this way the variation of the gas phases abundancy ratio with varying excitation conditions.