Statistical analysis of Fe abundances gradients in the Galaxy

Using the high precision data of the proper motions and parallaxes from Hip parcos catalogue, we obtained the orbital parameters of 1302 stars in the G alaxy based on the mass distribution model provided by Alien and Santillan. Fe abundances of 1295 stars among our samples were analyzed. With the corr elation analyses between [Fe/H] and orbital parameters, we obtained that th e Fe gradient is - 0.057 +/- 0.007 dex/kpc along the direction of the maxim um galactocentric distance (here-after DG(max)) in the range of 8.5 kpc < D G(max) < 17 kpc. We also got the result that the vertical gradient is steep er than the radial gradient. Furthermore, we divided the samples into two s ubgroups: giants and dwarfs; F, G and K stars; and then analyzed them respe ctively. Our results show that the gradient becomes flatter and flatter fro m giants to dwarfs, from F type to G and K type stars. We also divided the samples into disk and halo stars using maximum vertical distance Z(max) = 1 kpc as the criterion and got the result that the abundances of the disk st ars are much higher than that of the halo stars. Our work suggests the exis tence of the galactic gradient and supports those chemical evolution medels which show that the halo was formed before the disk at the early stage of the Galaxy.