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THE GALACTIC BULGE

THE GALACTIC BULGE. B. Barbuy IAG - Universidade de S ã o Paulo. S. Ortolani, E. Bica, M. Zoccali, V. Hill, D.Minniti, A. Renzini, A. Gomez, C. Babusiaux. Galactic bulge:. Template for stellar populations in Ellipticals and bulge of spirals

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THE GALACTIC BULGE

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  1. THE GALACTIC BULGE B. Barbuy IAG - Universidade de São Paulo S. Ortolani, E. Bica, M. Zoccali, V. Hill, D.Minniti, A. Renzini, A. Gomez, C. Babusiaux

  2. Galactic bulge: • Template for stellar populations in Ellipticals and bulge of spirals • Spectra provide metallicity, kinematics - field and globular clusters • Formation of the bulge: secular evolution or classical scenario, or satellite accretion • More recent evidence: X-shape bulge; He-enrichment Chemical enrichment by massive spinstars

  3. Outline: • Interest of studies on Galactic bulge • Data available on metallicity, kinematics in field bulge stars • More recent evidence: X-shape bulge; He-rich? • Metal-poor globular clusters in the inner bulge

  4. VVV: 84 million stars (Saito+ 2012)

  5. Multi-object high-res spectroscopy needed – not logical to do stars one by one FLAMES: 7 stars with UVES – R = 45,000 130 fibers with Giraffe – R = 22,000 Many programs: Bulge field Globular clusters

  6. METALLICITY (from high-res) 800 bulge field *s Zoccali+2008 l(°) b(°) BW 1.14 -4.2 -6° 0.2 -6 -1 0 -12 6553 5.2 -3

  7. KINEMATICS Babusiaux+ 2010 Baade’s Window: Metal-rich stars = bar Metal-poor stars = spheroid or thick disk b>-4o = Spheroid’s b<4o mix pops masks non-gradient

  8. Gonzalez et al. 2011 GIRAFFE spectra 650 stars

  9. Cescutti & Matteucci 2011,A&A,525,126 • Intense 10xSFR and short timescale of formation, 0.1-0.3Gyr • O and Mg: (Zoccali+06; Fulbright+06; Lecureur+07) • Si,S (Alves-Brito+10;Ryde+09;Bensby+10)

  10. Clarkson+ 2008 Sagittarius Window: l=1.25° b=-2.65° proper motion cleaned

  11. More recent evidence: • X-shape bulge • Microlensed metal-rich dwarfs: Helium-rich

  12. Saito et al. 2012 2 red clumps at ǂ distances ΔKs clump best seen in #8

  13. FLAMES: Vazquez, Zoccali et al. 2012

  14. CONCLUSIONS BULGE FIELD • If X-shape is an indication of a • pseudobulge, there remains to explain: • Kinematic difference between metal-poor • and metal-rich stars  but metal-poor • is a tiny fraction, and could be very old • alpha-element enhancement  but all • the structure could be very old • X-shape could have formed in the 1st 1Gyr

  15. Formation of inner bulge metal-poor Globular Clusters: First generation of massive fast-evolving stars: redshifts z~35 (Gao et al. 2010). Second generation of low-mass stars: forming in inner parts of galaxies.

  16. Metal-poor globular clusters in the Galactic Bulge Marin- Franch+09 added: NGC 6522: oldest so far

  17. Metal-poor GCs: Padova, Y=0.30, ages = 10, 13 Gyr BHB: Old

  18. Padova 13 Gyr Z=0.002, Y=0.23, 0.30 or He- Rich?

  19. CONCLUSIONS ON METAL-POOR GCs: Oldest objects in the Galaxy? Younger if He-enhanced: counts on blue extended HB needed Metal-rich inner bulge GC NGC 6553: RGBB/RC~0.3 – He not enhanced Field and GCs: further evidence on enrichment by fast rotating massive *s: Ba, Y, He

  20. SCIENCE ONLY FEASIBLE WITH MULTI-OBJECT HIGH-RES IN >8m CLASS E-ELT  Turn-off stars

  21. Microlensed dwarfs: high He

  22. Turn-off stars of bulge clusters: Age, metallicity, element abundance spread Oldest in the Galaxy, more subject to gravitational disruption, etc. Multiple populations in many of them? And clearly: multiple populations in the Galactic bulge, to be disentangled

  23. The End

  24. Chiappini+ 2011 Nature 472, 454 Excess Y confirms

  25. [Ba/Eu]=+0.5 s-fraction r-fraction Ba: 0.853 0.147 Eu: 0.027 0.973 From r-process only, Ba could not be more abundant than Eu  There is a significant s-production of Ba Excess Ba, Y predicted in massive spinstars (Barbuy+09)

  26. Evidence of enrichment by Massive spinstars Rotational mixing transports: 12C from He-burning core into H-rich layers 14N and 13C This primary 14N is transported back to He core  converted to 22Ne = main neutron source s-process occurs in hydrostatic He-core burning  primary s-process Ba is produced r-process in the explosion: Eu + some Ba

  27. SCIENCE ONLY FEASIBLE WITH MULTI-OBJECT HIGH-RES IN >8m CLASS PRESENTLY: FLAMES/VLT MIKE/MAGELLAN M2FS/MAGELLAN – 2013

  28. E-ELT TURN-OFF STARS

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