THICKNESS OF THIN STELLAR DISKS AND THE MASS OF THE DARK HALO

It is shown that thin galaxies with an apparent axial ratio b/a less-t han-or-equal-to 0.1 viewed edge-on have a geometrical thickness that c an be explained only by the presence of a massive dark halo. Analysis of the stability condition for stellar disks and the results of numeri cal simulation of N-body galaxies lead to the conclusion that the mini mum possible relative thickness z0/R0 of a collisionless disk decrease s with increasing relative mass-mu of the halo. Therefore, existing me asurements of the ratio z0/R0 for disks of normal galaxies can be used to estimate the relative halo mass.