Lacerta I and Cassiopeia III. Two Luminous and Distant Andromeda Satellite Dwarf Galaxies Found in the 3π Pan-STARRS1 Survey
Abstract
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 P1- and i P1-band imaging data. Both are luminous systems (MV ~ -12) located at projected distances of 20.°3 and 10.°5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756^{+44}_{-28}\,kpc and 772^{+61}_{-56}\,kpc, respectively, and corresponding M31-centric distances of 275 ± 7 kpc and 144^{+6}_{-4}\,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}\,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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2013
- DOI:
- 10.1088/0004-637X/772/1/15
- arXiv:
- arXiv:1305.5301
- Bibcode:
- 2013ApJ...772...15M
- Keywords:
-
- galaxies: individual: Andromeda XXXI Andromeda XXXII Cassiopeia III Lacerta I;
- Local Group;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 7 pages, 5 figures. Accepted for publication in ApJ