The discovery of seven extremely low surface brightness galaxies in the
  field of the nearby spiral galaxy M101
  Dwarf satellite galaxies are a key probe of dark matter and of galaxy
formation on small scales and of the dark matter halo masses of their central
galaxies. They have very low surface brightness, which makes it difficult to
identify and study them outside of the Local Group. We used a low surface
brightness-optimized telescope, the Dragonfly Telephoto Array, to search for
dwarf galaxies in the field of the massive spiral galaxy M101. We identify
seven large, low surface brightness objects in this field, with effective radii
of \(10 - 30\) arcseconds and central surface brightnesses of \(\mu_{g} \sim
25.5 - 27.5\) mag arcsec\(^{-2}\). Given their large apparent sizes and low
surface brightnesses, these objects would likely be missed by standard galaxy
searches in deep fields. Assuming the galaxies are dwarf satellites of M101,
their absolute magnitudes are in the range \(-11.6 \lesssim M_{V} \lesssim
-9.3\) and their effective radii are \(350\) pc \(-\) \(1.3\) kpc. Their radial
surface brightness profiles are well fit by Sersic profiles with a very low
Sersic index (\(n \sim 0.3 - 0.7\)). The properties of the sample are similar
to those of well-studied dwarf galaxies in the Local Group, such as Sextans I
and Phoenix. Distance measurements are required to determine whether these
galaxies are in fact associated with M101 or are in its foreground or
background.
