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Stellar populations and Kinematics of the Magellanic Clouds

Stellar populations and Kinematics of the Magellanic Clouds. R. A. Mendez, E. Costa,Maximiliano Moyano (Universidad de Chile), M.Pedreros (Universiadad de Tarrapacá, Chile), Carme Gallart & Noelia Noel (IAC, Spain).

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Stellar populations and Kinematics of the Magellanic Clouds

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  1. Stellar populations and Kinematics of the Magellanic Clouds R. A. Mendez, E. Costa,Maximiliano Moyano (Universidad de Chile),M.Pedreros (Universiadad de Tarrapacá, Chile),Carme Gallart & Noelia Noel (IAC, Spain) • Project started in 2001 aimed at determining the motion of the SMC wrt 10 background QSOs. [Costa et al. 2008, accepted to AJ] “QSO method” • A complimentary study of the stellar populations and Star Formation History, through deep (Rlim 24) CMDs reaching the oldest MS turnoff in the 10 QSO fields, plus 4 specially selected fields (,  for gradients). [Noel et al., AJ, 2007, 133, 2037] • Proper motions + Vrad => space velocity vector => constraints on the orbit. • Our project produces true space velocities for the MCs, eliminating the need to make assumptions regarding the shape of the orbits. • Knowledge is crucial to determine dynamical status of SMC wrt the LMC & MW. • To our understanding of the evolution and origin of the Magellanic System. SOCHIAS, Enero 2009, René A. Méndez

  2. Reported here Fields observed using 100-inch at LCO (magenta) Fields observed using WFI in La Silla (yellow) SOCHIAS, Enero 2009, René A. Méndez

  3. Las Campanas Obs. Iréneé du Pont 2.5m + Tek 2kX2k (24 μm) • Time-base 6 yrs  £0.5 mas yr-1 per QSO,on 10 QSO fields on SMC, +1 “bonus” bright QSO on LMC, • FOV 8.85 x 8.85 arc-min2 and0.26 arc-secpix-1, • QSOs R ~ 19–20, texp= 600 sec, S/NQSO³ 150 per exposure, seeing ~0.7”–1.3” • R-band astrometry within 1.5 hr from meridian, • Differential Chromatic Refraction frames (3.5 hrs), • Deep B, I-band for CMD (ref stars + Galactic contamination+ MCs stellar pops) SOCHIAS, Enero 2009, René A. Méndez

  4. LMC Center-of-mass PM 41 reference stars (LMC) QSO 0036-7225 Jones, Klemola & Lin, AJ, 1994 “E pour si muove…” Kinematical correction: LMC rotation… Center of mass:Perspective effect… LMC Vector-point diagram… Cleaned to sm£ 0.5 mas y-1 SOCHIAS, Enero 2009, René A. Méndez

  5. “As observed” PM 44 reference stars (SMC) Center-of-mass PM Bright QSO QSO 0557-6713 LMC CMD SMC CMD Faint QSO SMC Vector-point diagram… Cleaned to sm£ 0.7 mas y-1 SOCHIAS, Enero 2009, René A. Méndez

  6. LMC: Vgc,t = 315 ± 20 km s-1 Vgc,r = 86 ± 17 km s-1 Vgc,t = 280 ± 24 km s-1 Vgc,r = 94 ± 17 km s-1 Vrot = 50 km s-1 Vrot = 120 km s-1 Large Vt , small Vr ß near perigalacticon SMC: Vgc,t = 258 ± 50 km s-1 Vgc,r = 20 ± 44 km s-1 84 ± 50 km s-1 Vrot = 50 km s-1 62 ± 63 km s-1 Vrot = 120 km s-1 105 ± 42 km s-1 Kallivayalil et al. 2006 (HST, 2yr baseline!) 142 ± 19 km s-1 Piatek et al. 2008 (HST, same data!) ~90 km s-1 Escape velocity (model, MLMC~2x1010 MSun) SOCHIAS, Enero 2009, René A. Méndez

  7. Galaxy streams…. 2xLynden-Bell (1995): MCs, Draco, UMi, Carina & Sculptor : “Stream#2" Piatek et al. (2005) (m, q)LMC = (1.50 mas yr-1, 90o) (1.86±0.13 mas yr-1, 78±2o) for 50 km s-1(2.7s, 6.3s) (1.72±0.13 mas yr-1, 70±3o) for 120 km s-1 (1.7s, 6.4s) (m, q)SMC = (1.28 mas yr-1, 149o) (1.49±0.23 mas yr-1, 137±15o) (0.9s, 0.8s) SOCHIAS, Enero 2009, René A. Méndez

  8. The Magellanic Stream… Ram pressure stripping model: Heller and Rohlfs (1994) (Vt ,Vr)LMC = (352 , 107) km s-1 Tidal interaction model: Gardiner & Noguchi (1996) (Vt ,Vr)LMC = (286 , 80) km s-1 Measured LMC: (Vgc,t ,Vgc,r)=(315±20,86±17)50 (280±24,94±17)120 …tends to favour the tidal model for the MS... SOCHIAS, Enero 2009, René A. Méndez

  9. And….of course, the enclosed (dinamic) Galactic mass… MMW(d<50 kpc) = (7.3±0.9) x 1011 M€for 50 km s-1 (6.0±0.9) x 1011 M€for 120 km s-1 MMW(d<62 kpc) = (5.8±2.2) x 1011 M€ while theory predicts…MMW < 5.5x1011 M€Sakamoto et al. (2003) wip…8 more QSO fields in the making… SOCHIAS, Enero 2009, René A. Méndez

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