THE LOWER MAIN-SEQUENCE OF THE GLOBULAR-CLUSTER M3 WITH THE HUBBLE-SPACE-TELESCOPE - LUMINOSITY AND MASS FUNCTIONS

We present HST observations of the lower main sequence of the Galactic globular cluster M3. Our data, obtained with WFPC2 in the F814W and F 555W filters, sample a region centred about 4 arcmin away from the clu ster centre (at similar to 4.2 core radii). The photometry of the WF2, WF3 and WF4 fields extends down to V similar to 26.5 (I similar to 25 ), much deeper than any previous ground-based study on this cluster. T he resulting luminosity function (LF) for the main sequence covers the interval M-I=3-10.5, and reaches a maximum between M-I=8.5 and 9, sha ring in this feature the same behaviour as other clusters studied with HST so far. Making use of four different mass-luminosity (M-L) relati ons (theoretical and semi-empirical) a present-day mass function (MF) has also been obtained, which spans the mass interval similar or equal to 0.8-0.18 M.. Independent of the adopted M-L relation, the MF clear ly flattens out at the low-mass limits. However, no attempt has been m ade to take into account possible effects due, for instance, to mass s egregation and evaporation.