Nitrogen abundances and multiple stellar populations in the globular
  clusters of the Fornax dSph
  We use measurements of nitrogen abundances in red giants to search for
multiple stellar populations in the four most metal-poor globular clusters
(GCs) in the Fornax dwarf spheroidal galaxy (Fornax 1, 2, 3, and 5). New
imaging in the F343N filter, obtained with the Wide Field Camera 3 on the
Hubble Space Telescope, is combined with archival F555W and F814W observations
to determine the strength of the NH band near 3370 AA. After accounting for
observational errors, the spread in the F343N-F555W colors of red giants in the
Fornax GCs is similar to that in M15 and corresponds to an abundance range of
Delta([N/Fe])=2 dex, as observed also in several Galactic GCs. The spread in
F555W-F814W is, instead, fully accounted for by observational errors. The stars
with the reddest F343N-F555W colors (indicative of N-enhanced composition) have
more centrally concentrated radial distributions in all four clusters, although
the difference is not highly statistically significant within any individual
cluster. From double-Gaussian fits to the color distributions we find roughly
equal numbers of "N-normal" and "N-enhanced" stars (formally about 40% N-normal
stars in Fornax 1, 3, and 5 and 60% in Fornax 2). We conclude that GC
formation, in particular regarding the processes responsible for the origin of
multiple stellar populations, appears to have operated similarly in the Milky
Way and in the Fornax dSph. Combined with the high ratio of metal-poor GCs to
field stars in the Fornax dSph, this places an important constraint on
scenarios for the origin of multiple stellar populations in GCs.
