The LBT Satellites of Nearby Galaxies Survey (LBT-SONG): The Satellite
  Population of NGC 628
  We present the first satellite system of the Large Binocular Telescope
Satellites Of Nearby Galaxies Survey (LBT-SONG), a survey to characterize the
close satellite populations of Large Magellanic Cloud to Milky Way-mass,
star-forming galaxies in the Local Volume. In this paper, we describe our
unresolved diffuse satellite finding and completeness measurement methodology
and apply this framework to NGC 628, an isolated galaxy with $\sim1/4$ the
stellar mass of the Milky Way. We present two new dwarf satellite galaxy
candidates: NGC 628 dwA, and dwB with $\text{M}_{\text{V}}$ = $-12.2$ and
$-7.7$, respectively. NGC 628 dwA is a classical dwarf while NGC 628 dwB is a
low-luminosity galaxy that appears to have been quenched after reionization.
Completeness corrections indicate that the presence of these two satellites is
consistent with CDM predictions. The satellite colors indicate that the
galaxies are neither actively star-forming nor do they have the purely ancient
stellar populations characteristic of ultrafaint dwarfs. Instead, and
consistent with our previous work on the NGC 4214 system, they show signs of
recent quenching, further indicating that environmental quenching can play a
role in modifying satellite populations even for hosts smaller than the Milky
Way.
