Tip of the red giant branch distance to the nearby dwarf galaxy [TT2009]
  25 in the NGC 891 group
  Dwarf galaxies are key objects for small-scale cosmological tests like the
abundance problems or the planes-of-satellites problem. It is therefore a
crucial task to get accurate information for as many nearby dwarf galaxies as
possible. Using extremely deep, ground-based $V$ and $i$-band Subaru Suprime
Cam photometry with a completeness of $i=27$ mag, we measure the tip of the red
giant branch distance for the dwarf galaxy [TT2009] 25. This dwarf resides in
the field around the Milky Way-analog NGC 891. By using a Bayesian approach, we
measure a distance of $10.28^{+1.17}_{-1.73}$ Mpc, which is consistent with the
distance of NGC 891, thus we confirm it as a member of NGC 891. The dwarf
galaxy follows the scaling relations defined by the Local Group dwarfs. We do
not find an extended stellar halo around [TT2009] 25. In the small field of
view of 100 kpc covered by the survey, only one bright dwarf galaxy and the
giant stream are apparent. This is comparable to the Milky Way, where one
bright dwarfs reside in the same volume, as well as the Sagittarius stream -
excluding satellites which are farther away but would be projected in the
line-of-sight. It is thus imperative to survey for additional dwarf galaxies in
a larger area around NGC 891 to test the abundance of dwarf galaxies and
compare it to the number of satellites around the Milky Way.
