We use deep wide-field photometry from the Large Binocular Camera to study the stellar and structural properties of the recently discovered Andromeda X and Andromeda XVII ( And X and And XVII ) dwarf galaxies .
Using the mean apparent magnitude of the horizontal branch ( HB ) , we derive distances of 621 \pm 20 kpc to And X and 734 \pm 23 kpc to And XVII , closer by > 60 kpc than the previous estimates which were based on red giant branch ( RGB ) observations .
Thus our results warrant against the use of the RGB tip method for determining distances to systems with sparsely populated RGBs , and show how crucial HB observations are in obtaining accurate distances in systems such as these .
We find that And X is a relatively faint ( M _ { V } = - 7.36 ) , highly elongated ( \epsilon = 0.48 ) system at a distance of 174 \pm 62 kpc from Andromeda .
And XVII is brighter ( M _ { V } = - 8.61 ) with an M31-centric distance of 73 kpc which makes it one of the closest satellites to Andromeda .
Both galaxies are metal-poor : we derive \langle [ Fe / H ] \rangle = - 2.2 for And X , while And XVII shows \langle [ Fe / H ] \rangle = -2.0 , consistent with the relation of higher luminosity dwarfs being more metal-rich .
Additionally , both galaxies show considerable intrinsic spreads in metallicity ( 0.2 and 0.3 dex for And X and And XVII respectively ) , consistent with multiple stellar populations .