Luminosity function and mass segregation in M92

Abstract

We present WFPC2-HST observations of the lower main sequence of the galactic globular cluster M92 (NGC6341), extending down to V ~= 27. Our data, which cover a region of the cluster extending from the very center out to r ~= 380 arcsec, show that the slope of the luminosity function becomes flatter going towards the center of the cluster, as expected if M92 is a dynamically relaxed system. The slope of the inferred power-law mass function we computed ranges from x ~= 0.7 for the field centered at r = 18.61 core radii, to x ~= 0.3 for the annular field centered at r = 10.61 core radii, where a value of 14 arcsec has been used for the core radius of M92. Such a result, obtained without making any use of dynamical theoretical models, shows that segregation effects are at work in M92.