SPECTROSCOPY OF THE THREE DISTANT ANDROMEDAN SATELLITES CASSIOPEIA III, LACERTA I, AND PERSEUS I

• Published in: Astrophysical journal. Letters Vol. 793; no. 1; pp. 1 - 5
• Main Authors: Martin, Nicolas F, Chambers, Kenneth C, Collins, Michelle L M, Ibata, Rodrigo A, Rich, R Michael, Bell, Eric F, Bernard, Edouard J, Ferguson, Annette M N, Flewelling, Heather, Kaiser, Nicholas, Magnier, Eugene A, Tonry, John L, Wainscoat, Richard J
• Format: Journal Article
• Language: English
• Published: United States 20.09.2014
• Subjects: Andromeda Galaxy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Dispersions; Dwarf galaxies; EMISSION SPECTROSCOPY; GALAXIES; HYDROGEN; IRON; LIMITING VALUES; LUMINOSITY; MASS; METALLICITY; Satellites; Spectroscopy; STARS; Texts; VISIBLE RADIATION
• ISSN: 2041-8213; 2041-8205; 2041-8213
• DOI: 10.1088/2041-8205/793/1/L14

We present Keck II/DEIMOS spectroscopy of the three distant dwarf galaxies of M31 Lacerta I, Cassiopeia III, and Perseus I, recently discovered within the Pan-STARRS1 3[pi] imaging survey. The systemic velocities of the three systems ([upsilon] sub(r,helio) = -198.4 + or - 1.1 km s super(-1), -371.6 + or - 0.7 km s super(-1), and -326 + or - 3 km s super(-1), respectively) confirm that they are satellites of M31. In the case of Lacerta I and Cassiopeia III, the high quality of the data obtained for 126 and 212 member stars, respectively, yields reliable constraints on their global velocity dispersions ([sigma] sub(vr) = 10.3 + or - 0.9 km s super(-1) and 8.4 + or - 0.6 km s super(-1), respectively), leading to dynamical-mass estimates for both of ~4 x 10 super(7) M sub([middot in circle]) within their half-light radius. These translate to V-band mass-to-light ratios of (ProQuest: Formulae and/or non-USASCII text omitted) and (ProQuest: Formulae and/or non-USASCII text omitted) in solar units. We also use our spectroscopic data to determine the average metallicity of the three dwarf galaxies ([Fe/H] = -2.0 + or - 0.1, -1.7 + or - 0.1, and -2.0 + or - 0.2, respectively). All these properties are typical of dwarf galaxy satellites of Andromeda with their luminosity and size.