LACERTA I AND CASSIOPEIA III. TWO LUMINOUS AND DISTANT ANDROMEDA SATELLITE DWARF GALAXIES FOUND IN THE 3[pi] PAN-STARRS1 SURVEY

• Published in: The Astrophysical journal 2013-07, Vol.772 (1), p.1-6
• Main Authors: Martin, Nicolas F, Slater, Colin T, Schlafly, Edward F, Morganson, Eric, Rix, Hans-Walter, Bell, Eric F, Laevens, Benjamin P M, Bernard, Edouard J, Ferguson, Annette M N, Finkbeiner, Douglas P
• Format: Article
• Language: English
• Subjects: Andromeda Galaxy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; DISTANCE; Dwarf galaxies; DWARF STARS; GALAXIES; Imaging; Local group (astronomy); Planes; SATELLITES; Surface brightness; SURFACES
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/772/1/15

We 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 sub(P1) - and i sub(P1) -band imaging data. Both are luminous systems (M sub(v) ~ -12) located at projected distances of 20[degrees].3 and 10[degrees].5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756 super(+44) sub(-28) kpc and 772 super(+61) sub(-56) kpc, respectively, and corresponding M31-centric distances of 275 + or - 7 kpc and 144 super(+6) sub(-4) kpc. The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (r sub(h) = 4.2 super(+0.4) sub(-0.5) arcmin or 912 super(+124) sub(-93) pc for Lac I; r sub(h) = 6.5 super(+1.2) sub(-1.0) arcmin or 1456 + or - 267 pc for Cas III) and consequently low surface brightness ( mu sub(0) ~ 26.0 mag arcsec super(-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 3[pi] Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.