the galactic bulge

THE GALACTIC BULGETHE GALACTIC BULGE

B. BarbuyB. Barbuy

IAG - Universidade de SIAG - Universidade de São Pauloo Paulo

S. Ortolani, E. Bica, M. Zoccali,V. Hill, D.Minniti, A. Renzini, A. Gomez, C. Babusiaux

Galactic bulge:Galactic bulge:

Template for stellar populations in EllipticalsTemplate for stellar populations in Ellipticals

and bulge of spirals and bulge of spirals Spectra provide metallicity, kinematicsSpectra provide metallicity, kinematics

- field and globular clusters- field and globular clusters Formation of the bulge: secular evolution orFormation of the bulge: secular evolution or

classical scenario, or satellite accretionclassical scenario, or satellite accretion More recent evidence:More recent evidence:

X-shape bulge; He-enrichmentX-shape bulge; He-enrichment

Chemical enrichment by massive spinstarsChemical enrichment by massive spinstars

Outline:Outline:

Interest of studies on Galactic bulge Interest of studies on Galactic bulge Data available on metallicity, kinematicsData available on metallicity, kinematics

in field bulge starsin field bulge stars More recent evidence: X-shape bulge; He-rich?More recent evidence: X-shape bulge; He-rich? Metal-poor globular clusters in the inner bulgeMetal-poor globular clusters in the inner bulge

VVV: 84 million stars (Saito+ 2012)

FLAMES:

7 stars with UVES – R = 45,000130 fibers with Giraffe – R = 22,000

Many programs:Bulge fieldGlobular clusters

Multi-object high-res spectroscopy needed – not logical to do stars one by one

800 bulge field *sZoccali+2008

l(°) b(°)BW 1.14 -4.2-6° 0.2 -6-1 0 -126553 5.2 -3

METALLICITY(from high-res)

Babusiaux+ 2010Baade’s Window:Metal-rich stars = bar

Metal-poor stars = spheroid or thick disk b>-4o =Spheroid’s

b<4o mix pops masks non-gradient

KINEMATICS

Gonzalez et al. 2011Gonzalez et al. 2011

GIRAFFE spectra650 stars

Cescutti & Matteucci Cescutti & Matteucci 2011,A&A,525,1262011,A&A,525,126

Intense 10xSFR Intense 10xSFR and short and short timescale of timescale of formation, formation, 0.1-0.1-0.3Gyr0.3Gyr

O and Mg: O and Mg: (Zoccali+06; (Zoccali+06; Fulbright+06; Fulbright+06; Lecureur+07)Lecureur+07)

Si,S (Alves-Si,S (Alves-Brito+10;Ryde+09Brito+10;Ryde+09;Bensby+10);Bensby+10)

Clarkson+2008

SagittariusWindow: l=1.25° b=-2.65°

proper motion cleaned

More recent evidence:More recent evidence:

X-shape bulgeX-shape bulge Microlensed metal-rich dwarfs: Helium-Microlensed metal-rich dwarfs: Helium-

rich rich

Saito et al. 2012

2 red clumps at ǂ distances

ΔKs clump best seen in #8

FLAMES: Vazquez, Zoccali et al. 2012

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 oldX-shape could have formed in the 1st 1Gyr

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.

Metal-poor globular clusters in the Galactic Bulge

Marin-Franch+09

added:NGC 6522: oldest so far

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

BHB:Old

Padova 13 Gyr Z=0.002, Y=0.23, 0.30

or

He-Rich?

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

SCIENCE ONLY FEASIBLE SCIENCE ONLY FEASIBLE WITH MULTI-OBJECT HIGH-WITH MULTI-OBJECT HIGH-

RES IN >8m CLASSRES IN >8m CLASS

E-ELT Turn-off stars

Microlensed dwarfs: high He

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

The End

Chiappini+ 2011Nature472, 454

Excess Yconfirms

[Ba/Eu]=+0.5

s-fraction r-fractionBa: 0.853 0.147Eu: 0.027 0.973

From r-process only, Ba could not be moreabundant than Eu There is a significant s-production of Ba

Excess Ba, Y predicted in massive spinstars

(Barbuy+09)

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-coreburning primary s-process Ba is produced

r-process in the explosion: Eu + some Ba

SCIENCE ONLY FEASIBLE SCIENCE ONLY FEASIBLE WITH MULTI-OBJECT HIGH-WITH MULTI-OBJECT HIGH-

RES IN >8m CLASSRES IN >8m CLASS

PRESENTLY: PRESENTLY: FLAMES/VLTFLAMES/VLT

MIKE/MAGELLANMIKE/MAGELLAN

M2FS/MAGELLAN – 2013M2FS/MAGELLAN – 2013

E-ELTE-ELT

TURN-OFF STARSTURN-OFF STARS