The luminosity function of the globular cluster NGC 6752 with the Hubble Space Telescope: evidence of mass segregation

Abstract

We present the luminosity function (LF) for the lower main sequence of the Galactic globular cluster NGC6752, as obtained from Hubble Space Telescope (HST) observations centred 2 arcmin from the cluster centre. We present data in the F814W and F555W filters. Our LF reaches down to M_I=11 or, translated to a mass function, to M~=0.12 Msolar. The LF reaches a maximum between M_I=8.5 and 9, and shows no indication of an increase towards lower luminosities/masses; this is at variance with some ground-based observations, but is similar to all other HST-based LFs. There is a clear indication of mass segregation since the relative numbers of bright/faint stars differ from that found in ground-based observations and in other clusters analysed with the HST.