TY - JOUR
T1 - Spectroscopy of the Three Distant Andromedan Satellites Cassiopeia III, Lacerta I, and Perseus I
AU - Martin, Nicolas F.
AU - Chambers, Kenneth C.
AU - Collins, Michelle L. M.
AU - Ibata, Rodrigo A.
AU - Rich, R. Michael
AU - Bell, Eric F.
AU - Bernard, Edouard J.
AU - Ferguson, Annette M. N.
AU - Flewelling, Heather
AU - Kaiser, Nicholas
AU - Magnier, Eugene A.
AU - Tonry, John L.
AU - Wainscoat, Richard J.
PY - 2014/9/20
Y1 - 2014/9/20
N2 - 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 3π imaging survey. The systemic
velocities of the three systems (v r, helio = -198.4
± 1.1 km s-1, -371.6 ± 0.7 km
s-1, and -326 ± 3 km s-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 (σvr = 10.3 ±
0.9 km s-1 and 8.4 ± 0.6 km
s-1, respectively), leading to dynamical-mass estimates
for both of ~4 × 107 M ⊙ within their
half-light radius. These translate to V-band mass-to-light ratios of
15^{+12}_{-9} and 8^{+9}_{-5} in solar units. We also use our
spectroscopic data to determine the average metallicity of the three
dwarf galaxies ([Fe/H] = -2.0 ± 0.1, -1.7 ±
0.1, and -2.0 ± 0.2, respectively). All these properties
are typical of dwarf galaxy satellites of Andromeda with their
luminosity and size.
AB - 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 3π imaging survey. The systemic
velocities of the three systems (v r, helio = -198.4
± 1.1 km s-1, -371.6 ± 0.7 km
s-1, and -326 ± 3 km s-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 (σvr = 10.3 ±
0.9 km s-1 and 8.4 ± 0.6 km
s-1, respectively), leading to dynamical-mass estimates
for both of ~4 × 107 M ⊙ within their
half-light radius. These translate to V-band mass-to-light ratios of
15^{+12}_{-9} and 8^{+9}_{-5} in solar units. We also use our
spectroscopic data to determine the average metallicity of the three
dwarf galaxies ([Fe/H] = -2.0 ± 0.1, -1.7 ±
0.1, and -2.0 ± 0.2, respectively). All these properties
are typical of dwarf galaxy satellites of Andromeda with their
luminosity and size.
KW - galaxies: individual (Cas III Lac I Per I)
KW - galaxies: kinematics and dynamics
KW - Local Group
KW - DWARF SPHEROIDAL GALAXIES
KW - UNIVERSAL MASS PROFILE
KW - LOCAL GROUP
KW - MILKY-WAY
KW - KINEMATICS
KW - SYSTEM
KW - XXVIII
U2 - 10.1088/2041-8205/793/1/L14
DO - 10.1088/2041-8205/793/1/L14
M3 - Article
VL - 793
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - 14
ER -