THE GALACTIC BULGE

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B. Barbuy

THE GALACTIC BULGEB. BarbuyIAG - Universidade de São PauloS. Ortolani, E. Bica, M. Zoccali,V. Hill, D.Minniti, A. Renzini,A. Gomez, C. Babusiaux


Galactic bulge: Template for stellar populations in Ellipticalsand bulge of spirals Spectra provide metallicity, kinematics- field and globular clustersFormation of the bulge: secular evolution orclassical scenario, or satellite accretion More recent evidence:X-shape bulge; He-enrichmentenrichmentChemical enrichment by massive spinstars


VVV: 84 million stars (Saito+ 2012)


Multi-object high-res spectroscopyneeded – not logical to do stars one by oneFLAMES:7 stars with UVES – R = 45,000130 fibers with Giraffe – R = 22,000Many programs:Bulge fieldGlobular clusters


METALLICITY(from high-res)800 bulge field *sZoccali+2008l(°) b(°)BW 1.14 -4.2-6° 0.2 -6-1 0 -126553 5.2 -3


KINEMATICSBabusiaux+ 2010Baade’s Window:Metal-rich stars = barMetal-poor stars =spheroid or thick diskb>-4 o =Spheroid’sb


GIRAFFEspectra650 starsGonzalez et al. 2011


Cescutti & Matteucci2011,A&A,525,126 Intense 10xSFRand shorttimescale offormation, 0.1-0.3Gyr O and Mg:(Zoccali+06;Fulbright+06;Lecureur+07) Si,S (Alves-Brito+10;Ryde+09;Bensby+10)


Clarkson+2008SagittariusWindow:l=1.25°b=-2.65°propermotioncleaned


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


Saito et al. 20122 red clumps at Ƣdistances∆Ks clumpbest seen in #8


FLAMES: Vazquez, Zoccali et al. 2012


CONCLUSIONS BULGE FIELDIf X-shape is an indication of apseudobulge, there remains to explain:•Kinematic difference between metal-poorand metal-rich stars but metal-pooris a tiny fraction, and could be very old•alpha-element enhancement but allthe structure could be very oldX-shape could have formed in the 1 st 1Gyr


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


Metal-poor globular clusters in the Galactic BulgeMarin-Franch+09added:NGC 6522:oldestso far


Metal-poor GCs:Padova, Y=0.30, ages = 10, 13 GyrBHB:Old


Padova 13 Gyr Z=0.002, Y=0.23, 0.30orHe-Rich?


CONCLUSIONS ON METAL-POOR GCs:Oldest objects in the Galaxy?Younger if He-enhanced: counts onblue extended HB neededMetal-rich inner bulge GC NGC 6553:RGBB/RC~0.3 – He not enhancedField and GCs: further evidence on enrichmentby fast rotating massive *s: Ba, Y, He


SCIENCE ONLY FEASIBLEWITH MULTI-OBJECT HIGH-RES IN >8m CLASSE-ELT Turn-off stars


Microlensed dwarfs: high He


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


The End


Chiappini+2011Nature472, 454Excess Yconfirms


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


Evidence of enrichment by Massive spinstarsRotational mixing transports:12C from He-burning core into H-rich layers 14 N and 13 CThis primary 14 N is transported back to He core converted to 22 Ne = main neutron sources-process occurs in hydrostatic He-coreburning primary s-process Ba is producedr-process in the explosion: Eu + some Ba


SCIENCE ONLY FEASIBLEWITH MULTI-OBJECT HIGH-RES IN >8m CLASSPRESENTLY:FLAMES/VLTMIKE/MAGELLANM2FS/MAGELLAN – 2013


E-ELTELTTURN-OFF STARS

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