The following document lists the file abstract/TBANIA_SH_HLC.abs
from catalogue VI/111.
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===================================================================== ==> In this proposal, more time is being requested for TBANIA.TMB_2 ===================================================================== Large-scale surveys of the Galactic plane indicate that most of the molecular gas in the Galaxy is translucent. Chemical models of translucent clouds indicate that they are the transition objects between clouds with most of their carbon in atomic form and most of their carbon in CO: translucent clouds are the simplest clouds in which molecules exist in abundance and where photoprocesses dominate their chemistry. Only at high galactic latitudes are translucent clouds easily detected. We have begun a program to study the photochemistry of carbon and the major tracers of its chemical phases CO, [CI], and [CII], as well as dust, in a sample of translucent high latitude clouds. According to chemical models, the C+ column density in homogeneous translucent clouds should be similar to that of [CI]. Although we are using the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) to add [CI] observations of high latitude gas to the existing CO database, C+ observations are entirely missing. We propose to conduct a detailed study of the translucent high latitude cloud G294.4-14.3 with ISO. We wish to map the fine structure line of [CII] on a grid of points which extends from the mostly molecular central regions of the cloud to its photodissociated edges, where the volume filling factor of C+ is expected to be the highest. In addition, we wish to make sensitive measurements of the dust continuum at 120, 160, and 200 microns in order to infer the opacity of the dust, which heats the gas and shields it from UV radiation. Combined with existing and planned observations of [CI] and CO in the cloud, these measurements will for the first time make it possible to observationally constrain the carbon photochemistry of translucent molecular gas.