Metalpoor globular clusters of the Galactic bulge

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Metal-poor globular clustersof the Galactic bulge

• B. Barbuy
• IAG - Universidade de São Paulo

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VLT-UVES, Flames, Gemini-Phoenix, (Crires)?

• M. Zoccali, V. Hill, A. Renzini, S. Ortolani,
• D. Minniti, M. Asplund, E. Bica, B. Dias,
• A. Gomez, A. Alves-Brito, J. Meléndez,
• R.M. Rich, L. Pasquini, B. Gustafsson, N. Ryde

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• Formation of Globular Clusters
• Major merger models with metal-rich clusters
• forming during mergers, metal-poor ones form
• in original spirals not a dominant process
• b) Metal-poor GCs form in dwarf galaxies within
• the protogalactic potential, and metal-rich
  ones
• form later in a second phase
• c) Accretion scenarios a massive galaxy core
• forms metal-rich GCs, and metal-poor ones
• are accreted from dwarf galaxies
• (Strader et al. 2005)?

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d) scenario (c) is compatible with an inside-out
picture, in which case metal-poor clusters
could also form first in the bulge, and should be
very old e) Bekki (2005) metal-poor GCs formed
before reionization and process was truncated
at z5 to 15 f) Bars form bulges in this
case bulge stars should be disk stars
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Globular clusters in the Galaxy Total
160 Projected towards the bulge 80 within
20x20, Rlt 4kpc 65 clusters
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10x 10
?metal-poor Fe/H-1.0 ?-metal-rich Fe/Hgt-0.6
metal-poor Fe/Hlt-1.6 (halo?)?
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BHB Fe/H -1.0
HP1 UVES
OthersFLAMES (Phoenix)?
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4 fields field and clusters Zoccali et
al. 2007, 2008 Bulge metallicity
distribution from 1000 field giants
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metal-poor clusters fields
NGC 6325 NGC 6355
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Al3 NGC 6642
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Evidences for old bulge
2 metal-rich g.c. OLD
Ortolani et al. 1995, Nature, 377, 701
also Feltzing Gilmore 01
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Bulge LF N6528 (solid) field (dotted) ? bulge
field is old
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Zoccali et al. 2003
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13 Gyr Z0.004
11Gyr
13Gyr
16Gyr
Z0.0001
Lee et al. 1994 ApJ 423 248
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• BHB with
• Fe/H-1.0
• very old
• Ter4normal
• halo

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Na/O vs. Fe/H
O/Mg vs. Fe/H
Alves-Brito et al. 2008b
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Ca/Fe vs. Fe/H

• AGs
• ? Disco
• Reddy et al. 2006
• o Bojo
• Fulbright et al. 2007

Alves-Brito 2008 PhD thesis
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N6558-42
preliminary work
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CONCLUSIONS
Several Fe/H-1 clusters in the bulge may be
the oldest objects in the Galaxy
a-element overabundances (O,Mg, Si)? indicate a
fast chemical enrichment
BHB globulars seem different from thick disk
and halo
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Fields
FLAMES Data
Better coverage needed
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The End
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Côté 1999
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HP-1 VLT-UVES
2 stars, V17, 3h
Fe/H-1.0 O,Mg,Eu/Fe0.3 Si/Fe0.3 Ca,Ti/F
e0 Barbuy et al. 2006 AA, 449, 349
Ortolani et al. 1997 MNRAS 284, 692 NTT(1994),
seeing0.5
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Why Oxygen is important ? high oxygen-to-iron indi
cates fast early enrichment
Matteucci Brocato 1990, ApJ, 365, 539
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Coelho et al. 2001 cooler giants show TiO bands