1. B. Barbuy IAG - Universidade de São Paulo
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

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

7. FLAMES: 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

8. METALLICITY
(from high-res)
800 bulge field *s
Zoccali+2008
l(°) b(°) BW
-6°

9. 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

10. Gonzalez et al. 2011
GIRAFFE
spectra
650 stars

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

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

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

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

15. FLAMES: Vazquez, Zoccali et al. 2012

16. 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

17. 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.

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

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

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

22. 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

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

24. Microlensed dwarfs: high He

28. 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

29. The End

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

34. [Ba/Eu]=+0.5
s-fraction r-fraction
Ba:
Eu:
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)

35. 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

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

37. E-ELT
TURN-OFF STARS