the high galactic latitude molecular clouds are generally not located near intense sources of far-ultraviolet (fuv) radiation. most of these objects are translucent clouds: that is, the densities and temperatures measured for the cores are typical of diffuse clouds. because of the former property, molecules are able to form in abundance in translucent clouds. however, since the visual extinction is low (av < 2 typically), the ambient radiation field plays an important role in their chemistry. in the cores of translucent clouds the visual extinction is such that h2 -> hi and cii -> c -> co photochemistry is occuring. these objects make ideal laboratories for testing chemical models of regions with low fuv field intensities. however, few observations have been made toward intermediate-density molecular clouds with no enhanced fuv flux. observations of a variety of atomic and molecular species can provide important constraints for interstellar chemistry. in particular, for cloud complexes which are both nearby and have accurately known distances, a multi-species observational program can provide quite detailed information about the physical state of the gas. in addition to parameters like volume number density and kinetic temperature, an accurate measurement of the cooling rate of the gas can be measured. missing from, and vital to, any complete characterization of the physical state of the atomic and molecular interstellar medium of these objects are direct measurements of ionized carbon. iso lws observations of cii will be used in conjunction with existing ci, co, and hi data to study the gas properties of atomic/molecular cores identified in a sample of nearby (d<200 pc) high galactic latitude translucent molecular clouds. iso measurements of cii emission from a sample of translucent clouds with optically determined distances should give the cooling rate as a function of density and av. they can also provide important constraints on models for photodissociation regions (pdrs) in translucent clouds near weak fuv radiation fields.
Instrument
LWS02
Temporal Coverage
1998-02-05T19:27:28Z/1998-02-05T20:17:14Z
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.
European Space Agency, BANIA et al., 1999, 'PROBING THE STRUCTURE OF NEARBY TRANSLUCENT MOLECULAR CLOUDS: CONSTRAINING THE CHEMISTRY OF HIGH GALACTIC LATITUDE GAS', 1.0, European Space Agency, https://doi.org/10.5270/esa-vfibgcg
