Optical-NIR analysis of globular clusters in the IKN dwarf spheroidal: a
  complex star formation history
  Age, metallicity and spatial distribution of globular clusters (GCs) provide
a powerful tool to reconstruct major star-formation episodes in galaxies. IKN
is a faint dwarf spheroidal (dSph) in the M81 group of galaxies. It contains
five old GCs, which makes it the galaxy with the highest known specific
frequency (SN=126). We estimate the photometric age, metallicity and spatial
distribution of the poorly studied IKN GCs. We search SDSS for GC candidates
beyond the HST field of view, which covers half of IKN. To break the
age-metallicity degeneracy in the V-I colour we use WHT/LIRIS Ks-band
photometry and derive photometric ages and metallicities by comparison with SSP
models in the V,I,Ks colour space. IKN GCs' VIKs colours are consistent with
old ages ($\geq\!8$ Gyr) and a metallicity distribution with a higher mean than
typical for such a dSph ([Fe/H$]\!\simeq\!-1.4_{-0.2}^{+0.6}$ dex). Their
photometric masses range ($0.5 <{\cal M_{\rm GC}}<4\times10^5M_\odot$) implies
a high mass ratio between GCs and field stars, of $10.6\%$. Mixture model
analysis of the RGB field stars' metallicity suggests that 72\% of the stars
may have formed together with the GCs. Using the most massive GC-SFR relation
we calculate a SFR of $\sim\!10M_\odot/$yr during its formation epoch. We note
that the more massive GCs are closer to the galaxy photometric centre. IKN GCs
also appear spatially aligned along a line close to the IKN major-axis and
nearly orthogonal to the plane of spatial distribution of galaxies in the M81
group. We identify one new IKN GC candidate based on colour and PSF analysis of
the SDSS data. The evidence towards i) broad and high metallicity distribution
of the field IKN RGB stars and its GCs, ii) high fraction and iii), spatial
alignment of IKN GCs, supports a scenario for tidally triggered complex IKN's
SFH in the context of interactions with galaxies in the M81 group.
