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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

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

galactic bulge
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

outline
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
slide7

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

slide8

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

slide9

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

gonzalez et al 2011
Gonzalez et al. 2011

GIRAFFE

spectra

650 stars

cescutti matteucci 2011 a a 525 126
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)
slide12

Clarkson+

2008

Sagittarius

Window:

l=1.25°

b=-2.65°

proper

motion

cleaned

more recent evidence
More recent evidence:
  • X-shape bulge
  • Microlensed metal-rich dwarfs: Helium-rich
slide14

Saito et al. 2012

2 red clumps at ǂ

distances

ΔKs clump

best seen in #8

slide16

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
slide17

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.

slide18

Metal-poor globular clusters in the Galactic Bulge

Marin-

Franch+09

added:

NGC 6522:

oldest

so far

slide20

Metal-poor GCs:

Padova, Y=0.30, ages = 10, 13 Gyr

BHB:

Old

slide22

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

slide28

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

slide32

Chiappini+

2011

Nature

472, 454

Excess Y

confirms

slide34

[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)

slide35

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

science only feasible with multi object high res in 8m class1

SCIENCE ONLY FEASIBLE WITH MULTI-OBJECT HIGH-RES IN >8m CLASS

PRESENTLY: FLAMES/VLT

MIKE/MAGELLAN

M2FS/MAGELLAN – 2013

e elt

E-ELT

TURN-OFF STARS

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