Discovery of Isolated, Quenched, and Likely Backsplash Galaxies near M101

I report the discovery of three faint, semi-resolved quiescent dwarf galaxies, which are strong backsplash candidates associated with the nearby satellite-poor spiral M101 (D ~ 7 Mpc). The galaxies lie in a magnitude range MV ~ -7.65 to -8.4 and half-light radii rh ~ 110 to 229 pc. Shapiro DG-I (Sha DG-I/MAGE1412+5650) is a concurrently discovered, likely backsplash isolated dwarf galaxy. Shapiro DG-II (Sha DG-II) is a smaller, faint dwarf and a likely satellite companion to the SMC-mass galaxy NGC 5585 (D ~ 6.84 Mpc). Shapiro DG-III (Sha DG-III) is a faint, isolated dwarf on the edge of the ultra-faint regime, and a strong backsplash candidate. The three candidates lie within the search area beyond the virial radius of M101 ~250 kpc up to 350 kpc. A nondetection of UV emission coincident with the dwarf galaxies in GALEX indicates a lack of recent star formation. Hydrodynamical simulations predict backsplash quenching as the primary quenching method for dwarf galaxies outside of the virial radii but within ~1 Mpc of their hosts. The newly discovered candidates likely provide a local observational example of this process. In this work, archival and follow-up observations are compared to simulations and abundance models, and a pathway is created for deeper imaging and analysis to better understand the evolution of these galaxies.