Martin, Nicolas F.Slater, Colin T.Schlafly, Edward F.Morganson, EricRix, Hans-WalterBell, Eric F.Laevens, Benjamin P. M.Bernard, Edouard J.Ferguson, Annette M. N.Finkbeiner, DouglasBurgett, William S.Chambers, Kenneth C.Hodapp, Klaus W.Kaiser, NicholasKudritzki, Rolf-PeterMagnier, Eugene A.Morgan, Jeffrey S.Price, Paul A.Tonry, John L.Wainscoat, Richard J.2017-07-182013Martin, Nicolas F., Colin T. Slater, Edward F. Schlafly, Eric Morganson, Hans-Walter Rix, Eric F. Bell, Benjamin P. M. Laevens, et al. 2013. “Lacerta I and Cassiopeia III. Two Luminous and Distant Andromeda Satellite Dwarf Galaxies Found in the 3π Pan-STARRS1 Survey.” The Astrophysical Journal 772 (1) (June 28): 15. doi:10.1088/0004-637x/772/1/15.0004-637Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:33462058We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r P1- and i P1-band imaging data. Both are luminous systems (MV ~ –12) located at projected distances of 20fdg3 and 10fdg5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of $756^{+44}_{-28}{\rm \,kpc}$ and $772^{+61}_{-56}{\rm \,kpc}$, respectively, and corresponding M31-centric distances of 275 ± 7 kpc and $144^{+6}_{-4}{\rm \,kpc}$. The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes ($r_h = 4.2^{+0.4}_{-0.5}$ arcmin or $912^{+124}_{-93}{\rm \,pc}$ for Lac I; $r_h = 6.5^{+1.2}_{-1.0}$ arcmin or 1456 ± 267 pc for Cas III) and consequently low surface brightness (μ0 ~ 26.0 mag arcsec–2), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3π Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.en-USgalaxies: individual (Andromeda XXXI, Andromeda XXXII, Cassiopeia III, Lacerta I)Local GroupJournal Article2017-05-1620132017-07-1810.1088/0004-637X/772/1/15