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Galactic Structure

While the knowledge of the early phases of the evolution of the Universe is increasing with the incresing in size and angular resolution of the optical-near infrared telescopes, we remain astonishingly ignorant on the past history of our own Galaxy. There are at least two conflicting theory on the Galaxy formation (Searle and Zinn 1978 ApJ, 225, 357, Eggen, Lynden-Bell, Sandage, 1962, 136, 748), and we have little information on the star formation history of the halo and the thick disk (how many stars formed, where and when?), on the fragmentation processes (with which mass spectrum?). What is the fraction of gas left after the halo formation? Are there significant deviations on the extremes of the mass function, so that we can expect a large number of remnants and/or brown dwarfs? Also the structure of the halo and old disk is not well established . And though we have indications that the distribution function of the stars evolved with time, we do not know well the time scale and even less is known on the mechanism which is driving this evolution.

A wide field imager able to perform deep, multicolor surveys is a unique opportunity we have to better determine the ditribution function beyond the solar neighborood. From these surveys, repeated in time in order to have also the proper motion information we can extract:
1) luminosity functions of the different components (distinguished by proper motions and possibly radial velocities);
2) color distribution (fundamental to distinguish different stellar populations);
3) velocity distribution; velocity dispersion gradients
4) density distributions.

Though for the determination of the shape of the a wide field imaging facility in a smaller size telescope might be sufficent, there are a number of works for which the LBT prime focus instrument is a unique opportunity. The possible projects of interest for this instrument are briefly described below.


next up previous contents
Next: The faint end of Up: Stellar populations Previous: Stellar populations
Guido Buscema
1999-01-29