J/ApJ/808/108 M2FS stellar spectroscopy of Reticulum 2 (Walker+, 2015)
Magellan/M2FS spectroscopy of the Reticulum 2 dwarf spheroidal galaxy.
Walker M.G., Mateo M., Olszewski E.W., Bailey III J.I., Koposov S.E.,
Belokurov V., Evans N.W.
<Astrophys. J., 808, 108 (2015)>
=2015ApJ...808..108W 2015ApJ...808..108W (SIMBAD/NED BibCode)
ADC_Keywords: Abundances, [Fe/H] ; Galaxies, spectra ; Photometry, ugriz
Keywords: galaxies: dwarf; galaxies: individual: "Reticulum 2";
galaxies: kinematics and dynamics; Local Group;
methods: data analysis; techniques: spectroscopic
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
(νilos, median random error δνlos=1.4km/s), effective
temperature (Teff, δTef=478K), surface gravity (logg,
δlogg=0.63dex), and iron abundance ([Fe/H],
δ[Fe/H]=0.47dex). We use these results to confirm 17 stars as
members of Ret 2. From the member sample we estimate a velocity
dispersion of σνlos=3.6-0.7+1.0km/s about a mean of
<νlos≥64.31.2+1.2km/s in the solar rest frame (~-90.9km/s in
the Galactic rest frame), and a metallicity dispersion of
σ[Fe/H]=0.49-0.14+0.19dex 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)∼5Rhσνlos2/(2G)=2.4-0.8+1.4x105M☉
enclosed within projected halflight radius Rh∼32pc, with
mass-to-light ratio ∼2M(Rh)/LV=467-168+286 in solar units.
Description:
On 2015 February 19, we observed Ret 2 with the Michigan/Magellan
Fiber System (M2FS) on the 6.5m Magellan/Clay Telescope at Las
Campanas Observatory, Chile (5132-5186Å at effective resolution
R∼18000).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 152 38 M2FS stellar spectroscopy of Reticulum 2
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)
J/MNRAS/448/2717 : Bayesian analysis of resolved spectra (Walker+, 2015)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/776/80 : PAndAS view of Andromeda satellites. I. (Martin+, 2013)
J/AJ/144/4 : Properties of Local Group dwarf gal. (McConnachie+, 2012)
J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/MNRAS/380/281 : Faint galactic satellites spectrosc. survey (Martin+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [Ret2-]
6- 8 I03 --- Ret2 [4/178] Target Identifier
10- 11 I2 h RAh [3] Hour of Right Ascension (J2000)
13- 14 I2 min RAm [33/36] Minute of Right Ascension (J2000)
16- 20 F5.2 s RAs Second of Right Ascension (J2000)
22 A1 --- DE- [-] Sign of the Declination (J2000)
23- 24 I2 deg DEd [53/54] Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000)
34- 37 F4.1 arcmin R [1.2/18] Angular Separation from Center
39- 43 F5.2 mag gmag [17.3/20.7] Magnitude in g band (1)
45- 49 F5.2 mag rmag [16.8/20.3] Magnitude in r band (1)
51- 55 F5.1 --- S/N [1/16] Median Signal/Noise Ratio per pixel
57- 62 F6.1 km/s Vlos [16/309] Solar rest frame line-of-sight
velocity (νlos)
64- 68 F5.1 km/s e_Vlos [0.4/3.3] Uncertainty in Vlos
70- 75 F6.1 --- sVlos [-0.5/0.9] Skewness in Vlos
77- 83 F7.1 --- kVlos [2/4] Kurtosis in Vlos
85- 88 I4 K Teff [4494/6506] Effective Temperature
90- 93 I4 K e_Teff [50/1034] Uncertainty in Teff
95- 99 F5.1 --- sTeff [-0.4/2.1] Skewness in Teff
101-105 F5.1 --- kTeff [2/9.2] Kurtosis in Teff
107-110 F4.2 [cm/s2] logg [0.5/4.8] Log surface gravity
112-115 F4.2 [cm/s2] e_logg [0.1/1.3] Uncertainty in logg
117-121 F5.1 --- slogg [-1.7/0.8] Skewness in logg
123-127 F5.1 --- klogg [2.2/6.8] Kurtosis in logg
129-133 F5.2 [-] [Fe/H] [-3.6/-0.01] Metallicity
135-138 F4.2 [-] e_[Fe/H] [0.04/1.1] Uncertainty in [Fe/H]
140-144 F5.1 --- s[Fe/H] [-0.6/1.5] Skewness in [Fe/H]
146-150 F5.1 --- k[Fe/H] [2/5.7] Kurtosis in [Fe/H]
152 A1 --- Mm? Member of Ret 2? (Y/N)
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Note (1): g, r magnitudes from the photometry of K15 (Koposov et al.,
2015ApJ...805..130K 2015ApJ...805..130K), corrected for extinction using the dust maps
of Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Dec-2015