Scientific Aims

The main goals of this joint discussion

• To review the major surveys whose targets are stars.
• To appreciate the scientific goals and the byproducts of these surveys.
• To consider how well the techniques employed achieve these goals.
• To exchange ideas on how best to exploit the opportunities of future surveys.

Good surveys provide the lifeblood for astronomy. Without them the subject is moribund. Astronomers always need more complete samples of the particular objects around which their interest centres and which hold answers to their significant questions. Large resources of manpower, telescopes and data handling are going into current surveys, and even more are planned for future surveys. But how do we best go from the data output to answering our scientific questions?

The question will be posed with respect to the photometric and spectroscopic classification techniques required to identify stars of different types, given the specific types of data which are being provided by the large surveys. The MK System is a starting point, both historical and practical, but how well can physical parameters of stars be derived from the observational data, in view of calibration requirements or interstellar extinction or other factors? Stellar variability also provides distance data, but how do metallicity and extinction affect its reliability? Radial velocity and proper motion information will also be considered, while keeping an eye on the theoretical stellar structure and atmospheric models which translate all these data into the parameters of age and population and location that are meaningful for Galactic studies. Since the Milky Way is an average late-type spiral galaxy, it serves as an important model for the formation and evolution of this class of galaxies.

This joint discussion will dwell on the results for Galactic astronomy coming from the ingenuity, skill, and work of those currently involved with surveys. However these same people will recognize that the full potential of their surveys is only attained by critically examining each analysis method and by providing as many independent checks as possible on the data products and scientific interpretations. It is especially difficult to obtain secure information for the fainter objects which have photometry of lesser accuracy and spectra of lower signal to noise. The translation of data from survey specific filters into commonly used filters may not be straightforward. Follow up spectroscopy may be essential for adequate parameterization of the objects and calibration of the full samples.

As we reflect together in this meeting on the strengths and weaknesses of large surveys, we shall be able to rejoice in the former and learn how future surveys might give their best answers to astronomy's key questions this century.