TY - JOUR
T1 - MAGELLAN/M2FS SPECTROSCOPY of the RETICULUM 2 DWARF SPHEROIDAL GALAXY
AU - Walker, Matthew G.
AU - Mateo, Mario
AU - Olszewski, Edward W.
AU - Iii, John I.Bailey
AU - Koposov, Sergey E.
AU - Belokurov, Vasily
AU - Evans, N. Wyn
N1 - Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved.
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 182 stellar targets along the line of sight (LOS) to the newly discovered "ultrafaint" object Reticulum 2 (Ret 2). For 37 of these targets, the spectra are sufficient to provide simultaneous estimates of LOS velocity (νlos, median random error δνlos= 1.4 km s-1), effective temperature (Teff, Δ Teff K), surface gravity (loh g, δlog g = 0.63 dex), and iron abundance ([Fe/H], δ[Fe/H] = 0.47 dex). We use these results to confirm 17 stars as members of Ret 2. From the member sample we estimate a velocity dispersion of σνlos = 3.60.7+1.0km s-1 about a mean of 〈νlos〉 = 64.3-1.2+1.2 km s-1 in the solar rest frame ( ∼ -90.9 km s-1 in the Galactic rest frame), and a metallicity dispersion of σ [Fe/H] = 0.49-0.140.19 dex about a mean of 〈 [Fe/H]〉= -2.58-0.33+0.34. These estimates marginalize over possible velocity and metallicity gradients, which are consistent with zero. Our results place Ret 2 on chemodynamical scaling relations followed by the Milky Way's dwarf-galactic satellites. Under assumptions of dynamic equilibrium and negligible contamination from binary stars - both of which must be checked with deeper imaging and repeat spectroscopic observations - the estimated velocity dispersion suggests a dynamical mass of M(Rh)≈5Rhσνlos;2/(2G) = 2.4-0.8+1.4 × 105 M⊙enclosed within projected halflight radius Rh ∼32 pc, with mass-to-light ratio ≈2M (Rh)/LV = 467-168+286in solar units.
AB - We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 182 stellar targets along the line of sight (LOS) to the newly discovered "ultrafaint" object Reticulum 2 (Ret 2). For 37 of these targets, the spectra are sufficient to provide simultaneous estimates of LOS velocity (νlos, median random error δνlos= 1.4 km s-1), effective temperature (Teff, Δ Teff K), surface gravity (loh g, δlog g = 0.63 dex), and iron abundance ([Fe/H], δ[Fe/H] = 0.47 dex). We use these results to confirm 17 stars as members of Ret 2. From the member sample we estimate a velocity dispersion of σνlos = 3.60.7+1.0km s-1 about a mean of 〈νlos〉 = 64.3-1.2+1.2 km s-1 in the solar rest frame ( ∼ -90.9 km s-1 in the Galactic rest frame), and a metallicity dispersion of σ [Fe/H] = 0.49-0.140.19 dex about a mean of 〈 [Fe/H]〉= -2.58-0.33+0.34. These estimates marginalize over possible velocity and metallicity gradients, which are consistent with zero. Our results place Ret 2 on chemodynamical scaling relations followed by the Milky Way's dwarf-galactic satellites. Under assumptions of dynamic equilibrium and negligible contamination from binary stars - both of which must be checked with deeper imaging and repeat spectroscopic observations - the estimated velocity dispersion suggests a dynamical mass of M(Rh)≈5Rhσνlos;2/(2G) = 2.4-0.8+1.4 × 105 M⊙enclosed within projected halflight radius Rh ∼32 pc, with mass-to-light ratio ≈2M (Rh)/LV = 467-168+286in solar units.
KW - Local Group
KW - galaxies: dwarf
KW - galaxies: individual (Reticulum 2)
KW - galaxies: kinematics and dynamics
KW - methods: data analysis
KW - techniques: spectroscopic
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U2 - 10.1088/0004-637X/808/2/108
DO - 10.1088/0004-637X/808/2/108
M3 - Article
AN - SCOPUS:84940781590
VL - 808
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 108
ER -