{ A large sample of carbon stars in the LMCRussell
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چکیده
The application of multi-object instruments to nearby galaxies permits the spectroscopy of large samples of faint stars. Such data are needed to determine the kinematics and metallicity distributions of stellar systems, to complement the excellent photometric data now becoming available. Together, these data should reveal the star formation and evolutionary histories of Local Group galaxies. The Two-degree Field (2dF) instrument on the Anglo-Australian Telescope is described and some initial results are presented for a sample of 700 carbon stars in the Large Magellanic Cloud. The velocity precision is more than adequate for kine-matic studies, while the application of Principal Component Analysis techniques promises to yield an objective and quantitative classiication scheme for carbon stars. This may lead to a better understanding of the carbon stars themselves, as well as enhancing their use as tracers of the intermediate-age and old stellar populations. Another application of multi-bre spectroscopy, to a sample of main sequence stars in the glob-ular cluster 47 Tuc, illustrates the possibility of combining the data for many faint stars to yield composite spectra with relatively high signal-to-noise ratio. 1. The case for multi-object spectroscopy One of the surprises that arose during the preparations for IAU Symposium 192 was the imbalance between photometric and spectroscopic data. By analogy with recent developments in observational cosmology, where the combination of HST imaging and Keck spectroscopy is producing tremendous advances in the study of high redshift galaxies and quasars, we had expected that the most powerful facilities would already be in widespread use for the spectroscopy of stars in Local Group galaxies. However, the contributions to this meeting indicate that this has barely begun to happen.
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تاریخ انتشار 2007