* Astronomy

Title: d1005+68: A New Faint Dwarf Galaxy in the M81 Group
Author: Adam Smercina, Eric F. Bell, Colin T. Slater, Paul A. Price, Jeremy Bailin, Antonela Monachesi

We present the discovery of d1005+68, a new faint dwarf galaxy in the M81 Group, using observations taken with the Subaru Hyper Suprime-Cam. d1005+68's color-magnitude diagram is consistent with a distance of 3.98_{-0.43}^{+0.39} Mpc, establishing group membership. We derive an absolute V-band magnitude, from stellar isochrone fitting, of M_{V} = -7.94_{-0.50}^{+0.38}, with a half-light radius of r_{h} = 188_{-41}^{+39} pc. These place d1005+68 within the radius-luminosity locus of Local Group and M81 satellites and among the faintest confirmed satellites outside the Local Group. Assuming an age of 12 Gyr, d1005+68's red giant branch is best fit by an isochrone of [Fe/H] =-1.90±0.24. It has a projected separation from nearby M81 satellite BK5N of only 5 kpc. As this is well within BK5N's virial radius, we speculate that d1005+68 may be a satellite of BK5N. If confirmed, this would make d1005+68 one of the first detected satellites-of-a-satellite.

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