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J/ApJ/756/74     2MASS view of Sgr dSph. VII. Kinematics     (Frinchaboy+, 2012)

A 2MASS all-sky view of the Sagittarius dwarf galaxy. VII. Kinematics of the main body of the Sagittarius dSph. Frinchaboy P.M., Majewski S.R., Munoz R.R., Law D.R., Lokas E.L., Kunkel W.E., Patterson R.J., Johnston K.V. <Astrophys. J., 756, 74 (2012)> =2012ApJ...756...74F
ADC_Keywords: Stars, M-type ; Stars, giant ; Radial velocities ; Galaxies, IR ; Photometry, infrared Keywords: galaxies: individual: Sgr dSph; galaxies: kinematics and dynamics; Local Group Abstract: We have assembled a large-area spectroscopic survey of giant stars in the Sagittarius (Sgr) dwarf galaxy core. Using medium resolution (R∼15000), multifiber spectroscopy we have measured velocities of these stars, which extend up to 12° from the galaxy's center (3.7 core radii or 0.4 times the King limiting radius). From these high-quality spectra we identify 1310 Sgr members out of 2296 stars surveyed, distributed across 24 different fields across the Sgr core. Additional slit spectra were obtained of stars bridging from the Sgr core to its trailing tail. Our systematic, large-area sample shows no evidence for significant rotation, a result at odds with the ∼20km/s rotation required as an explanation for the bifurcation seen in the Sgr tidal stream; the observed small (≤4km/s) velocity trend primarily along the major axis is consistent with models of the projected motion of an extended body on the sky with no need for intrinsic rotation. The Sgr core is found to have a flat velocity dispersion (except for a kinematically colder center point) across its surveyed extent and into its tidal tails, a property that matches the velocity dispersion profiles measured for other Milky Way dwarf spheroidal (dSph) galaxies. We comment on the possible significance of this observed kinematical similarity for the dynamical state of the other classical Milky Way dSphs in light of the fact that Sgr is clearly a strongly tidally disrupted system. Description: Spectroscopic data were obtained using the Hydra spectrograph on the Blanco 4m telescope at Cerro Tololo Inter-American Observatory (CTIO) on the nights of 2003 July 19-22 and 2003 August 1-7. The spectral range covered was 7740-8740Å with R∼15000. We obtained supplementary data with the Modular Spectrograph on the DuPont 2.5m telescope on the nights of UT 2003 September 19 and 20. See section 5.1 File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 92 2296 Sagittarius stellar velocity data table5.dat 71 37 Supplementary radial velocity data on M giants observed with the DuPont telescope
See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/MNRAS/427/2647 : Sgr dSph stars spectral classification (McDonald+, 2012) J/A+A/520/A95 : Abundances of red giants in M54 and Sgr dSph (Carretta+, 2010) J/A+A/513/A62 : Sgr dSph VIMOS phot. and radial velocities (Giuffrida+, 2010) J/ApJ/708/1290 : A 2MASS view of the Sgr dSph. VI. (Chou+, 2010) J/A+A/465/815 : Abundances of Sgr dSph stars (Sbordone+, 2007) J/ApJ/670/346 : M giant stars in the Sgr dwarf galaxy. V. (Chou+, 2007) J/AJ/128/245 : M giant stars in the Sgr dwarf galaxy (Majewski+, 2004) J/A+A/414/503 : Abundances in the Sgr dSph (Bonifacio+, 2004) J/AJ/113/634 : The survival of Sagittarius dwarf galaxy (Ibata+ 1997) J/AJ/110/1141 : Variables in the Sagittarius dSph (Mateo+ 1995) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Field Sagittarius field name (1) 10- 25 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMSSs; J2000) 27- 31 F5.2 mag Kmag0 [8.8/14] Dereddened 2MASS K magnitude 33- 36 F4.2 mag (J-K)0 [0.5/1.4] Dereddened 2MASS J-K color index 38- 41 F4.2 mag E(B-V) [0.07/0.3] E(B-V) from Schlegel et al. 1998ApJ...500..525S 43- 49 F7.4 deg GLON Galactic Longitude 51- 58 F8.4 deg GLAT Galactic Latitude 60- 66 F7.3 deg Lambda [0.001/360] The Sgr longitude as viewed from the Sun (Λ) (G1) 68- 73 F6.1 km/s HRV [-356.7/301.2] Heliocentric radial velocity 75- 80 F6.1 km/s Vgsr [-336.4/318.5] Galactocentric radial velocity 82- 84 F3.1 km/s e_HRV [1.2/5] Mean error on radial velocity 86- 90 F5.2 --- R [5/61] Tonry-Davis ratio (1979AJ.....84.1511T) 92 A1 --- Mm [YN] Membership flag (Y=yes, N=no)
Note (1): Field are: ---------------------------------------------- Field GLON GLAT <E(B-V)> spec ---------------------------------------------- Major+00 5.51 -14.21 0.154 Major-04 4.92 -10.11 0.197 Major-02 5.20 -12.26 0.170 Major+02 5.91 -15.99 0.121 Major+04 6.26 -17.90 0.101 Major+06 6.47 -20.02 0.119 Major+08 6.57 -22.04 0.088 Major+10 6.88 -24.05 0.159 Major+12 6.89 -26.15 0.176 Minor-03 2.57 -14.47 0.089 Minor-02 3.75 -14.21 0.125 Minor-01 4.62 -14.29 0.155 Minor+01 6.55 -13.94 0.162 Minor+02 7.77 -13.81 0.206 Minor+03 8.51 -13.56 0.219 Minor+05 10.69 -13.27 0.204 SE+04 3.27 -17.20 0.100 SE+02 4.46 -15.57 0.118 NW+02 6.94 -12.58 0.173 NW+04 7.81 -10.87 0.265 SW+04 2.28 -11.79 0.121 SW+02 4.08 -12.99 0.153 NE+02 7.50 -15.27 0.118 ESE+07 3.46 -20.02 0.095 ---------------------------------------------- See Figure 1 and table 1 for further explanations.
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 16 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMSSs; J2000) 18- 22 F5.2 mag Kmag0 [9.7/12.4] Dereddened 2MASS K magnitude 24- 27 F4.2 mag (J-K)0 [0.9/1.3] Dereddened 2MASS J-K color index 29- 32 F4.2 mag E(B-V) [0/0.2] E(B-V) from Schlegel et al. 1998ApJ...500..525S 34- 37 F4.1 deg GLON Galactic Longitude 39- 43 F5.1 deg GLAT Galactic Latitude 45- 48 F4.1 deg Lambda [12.7/48.2] The Sgr longitude as viewed from the Sun (Λ) (G1) 50- 55 F6.1 km/s HRV [-133.2/144.2] Heliocentric radial velocity 57- 62 F6.1 km/s Vgsr [-120.7/165.7] Galactocentric radial velocity 64- 67 F4.2 --- CCP [0.2/0.95] Peak of the cross-correlation spectrum 69 I1 --- Q [4/7] Data quality (7=best; 0=worst) 71 A1 --- Mm [YN] Membership flag (Y=yes, N=no)
Global Notes: Note (G1): The Sgr coordinate system is described in Majewski et al. (2003ApJ...599.1082M) and is defined by virtue of the orientation of the extended tidal stream. However, we note that (as shown in that same reference; see their Figure 7) the main body of Sgr is canted by about 6° with respect to the mean orientation of the stream, so that our major and minor axis positions do not directly line up with the (Λ, B) system.
History: From electronic version of the journal References: Majewski et al. Paper I. 2003ApJ...599.1082M Majewski et al. Paper II. 2004AJ....128..245M Cat. J/AJ/128/245 Johnston et al. Paper III. 2005ApJ...619..800J Law et al. Paper IV. 2005ApJ...619..807L Chou et al. Paper V 2007ApJ...670..346C Cat. J/ApJ/670/346 Chou et al. Paper VI. 2010ApJ...708.1290C Cat. J/ApJ/708/1290
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Mar-2014
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