Abstract
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 (ν<inf>los</inf>, median random error δ<inf>νlos</inf>= 1.4 km s<sup>-1</sup>), effective temperature (T<inf>eff</inf>, Δ <inf>Teff</inf> K), surface gravity (loh g, δ<inf>log g</inf> = 0.63 dex), and iron abundance ([Fe/H], <sup>δ</sup>[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 σ<inf>νlos</inf> = 3.6<inf>0.7</inf><sup>+1.0</sup>km s<sup>-1</sup> about a mean of 〈ν<inf>los</inf>〉 = 64.3<inf>-1.2</inf><sup>+1.2</sup> km s<sup>-1</sup> in the solar rest frame ( ∼ -90.9 km s<sup>-1</sup> in the Galactic rest frame), and a metallicity dispersion of <sup>σ</sup> [Fe/H] = 0.49<inf>-0.14</inf><sup>0.19</sup> dex about a mean of 〈 [Fe/H]〉= -2.58<inf>-0.33</inf><sup>+0.34</sup>. 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(R<inf>h</inf>)≈5R<inf>hσνlos;</inf><sup>2</sup>/(2G) = 2.4<inf>-0.8</inf><sup>+1.4</sup> × 10<sup>5</sup> M<inf>⊙</inf>enclosed within projected halflight radius R<inf>h</inf> ∼32 pc, with mass-to-light ratio ≈2M (R<inf>h</inf>)/L<inf>V</inf> = 467<inf>-168</inf><sup>+286</sup>in solar units.
| Original language | English (US) |
|---|---|
| Article number | 108 |
| Journal | Astrophysical Journal |
| Volume | 808 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 1 2015 |
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Keywords
- galaxies: dwarf
- galaxies: individual (Reticulum 2)
- galaxies: kinematics and dynamics
- Local Group
- methods: data analysis
- techniques: spectroscopic
ASJC Scopus subject areas
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
MAGELLAN/M2FS SPECTROSCOPY of the RETICULUM 2 DWARF SPHEROIDAL GALAXY. / Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W; Iii, John I Bailey; Koposov, Sergey E.; Belokurov, Vasily; Evans, N. Wyn.
In: Astrophysical Journal, Vol. 808, No. 2, 108, 01.08.2015.Research output: Contribution to journal › Article
}
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
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 - galaxies: dwarf
KW - galaxies: individual (Reticulum 2)
KW - galaxies: kinematics and dynamics
KW - Local Group
KW - methods: data analysis
KW - techniques: spectroscopic
UR - http://www.scopus.com/inward/record.url?scp=84940781590&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84940781590&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/808/2/108
DO - 10.1088/0004-637X/808/2/108
M3 - Article
VL - 808
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 108
ER -