Stellar population and structural properties of dwarf galaxies and young
  stellar systems in the M81 group
  We use Hyper Suprime-Cam on the Subaru Telescope to investigate the
structural and photometric properties of early-type dwarf galaxies and young
stellar systems at the center of the M81 Group. We have mapped resolved stars
to $\sim2$ magnitudes below the tip of the red giant branch over almost 6.5
square degrees, corresponding to a projected area of $160\times160 \rm{kpc}$ at
the distance of M81. The resulting stellar catalogue enables a homogeneous
analysis of the member galaxies with unprecedented sensitivity to low surface
brightness emission. The radial profiles of the dwarf galaxies are
well-described by Sersic and King profiles, and show no obvious signatures of
tidal disruption. The measured radii for most of these systems are larger than
the existing literature values and we find the total luminosity of IKN
($\rm{M_{V,0}}=-14.29$) to be almost 3 magnitudes brighter than
previously-thought. We identify new dwarf satellite candidates, d1006+69 and
d1009+68, which we estimate to lie at a distance of $4.3\pm0.2$ Mpc and
$3.5\pm0.5$ Mpc. With $\rm{M_{V,0}}=-8.91\pm0.40$ and
$\rm{[M/H]}=-1.83\pm0.28$, d1006+69 is one of the faintest and most metal-poor
dwarf satellites currently-known in the M81 Group. The luminosity functions of
young stellar systems in the outlying tidal HI debris imply continuous star
formation in the recent past and the existence of populations as young as 30
Myr old. We find no evidence for old RGB stars coincident with the young
MS/cHeB stars which define these objects, supporting the idea that they are
genuinely new stellar systems resulting from triggered star formation in
gaseous tidal debris.
