The puzzle of metallicity and multiple stellar populations in the
  Globular Clusters in Fornax
  We examine the photometric data for Fornax clusters, focussing our attention
on their horizontal branch color distribution and, when available, on the RR
Lyr variables fraction and period distribution. Based on our understanding of
the HB morphology in terms of varying helium content in the context of multiple
stellar generations, we show that clusters F2, F3 and F5 must contain
substantial fractions of second generation stars (~54-65%). On the basis of a
simple chemical evolution model we show that the helium distribution in these
clusters can be reproduced by models with cluster initial masses ranging from
values equal to ~4 to ~10 times larger than the current masses. Models with a
very short second generation star formation episode can also reproduce the
observed helium distribution but require larger initial masses up to about
twenty times the current mass. While the lower limit of this range of possible
initial GC masses is consistent with those suggested by the observations of the
low metallicity field stars, we also discuss the possibility that the
metallicity scale of field stars (based on CaII triplet spectroscopy) and the
metallicities derived for the clusters in Fornax may not be consistent with
each other. The reproduction of the HB morphology in F2,F3,F5 requires two
interesting hypotheses: 1) the first generation HB stars lie all at "red"
colours. According to this interpretation, the low metallicity stars in the
field of Fornax, populating the HB at colours bluer than the blue side
((V-I)o<=0.3 or (B-V)o<=0.2) of the RR Lyrs, should be second generation stars
born in the clusters;a preliminary analysis of available colour surveys of
Fornax field provides a fraction ~20% of blue HB stars, in the low metallicity
range; 2) the mass loss from individual second generation red giants is a few
percent of a solar mass larger than the mass loss from first generation stars.
