The following document lists the file abstract/JTAUBER_ISO_GRAD.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
Spiral galaxies undergo chemical evolution as a result of the processing of material in the interior of stars, and the subsequent ejection of processed gas into the ISM. Thus the chemical state of a galaxy reflects its star formation history, material ejection and recycling phenomena, and the dynamical interaction of the different phases of the ISM. In particular the ratio of C to (13)C should evolve in time, as the abundance of the secondary species (13)C is enhanced over that of the primary species. Since the star formation rate is not homogeneous across a spiral galaxy (but is usually concentrated in its central region, at least in the initial stages of galactic evolution), in time a radial gradient of the isotopic ratios should be set up. A measurement of the gradient can thus set important constraints on the evolutionary history of a galaxy. We here propose to observe the 158 micron lines of ionized atomic carbon and its isotopic counterpart (13)CII in a range of positions along the Galactic plane to measure the distribution of the carbon isotopic ratio (13)C/C. This measure will be complementary to ground- based observations of molecular carbon species. Because of the long integration times required to detect the (13)CII lines, ISO is at present the only platform capable of carrying out these observations.