Globular Clusters with Multiple Populations as Remaining Cores of Primordial Galaxy Building Blocks

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Globular Clusters with Multiple Populations as
Remaining Cores of Primordial Galaxy Building
Blocks

• Young-Wook Lee
• Yonsei University, Seoul, South Korea
• Science with the GMT, Canberra, March 26, 2008

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Formation of the MW Galaxy Milestones

• 1. ELS 1962 Larson 1974 (Collapse)
• 2. Searle Zinn 1978 Toomre 1977 (Accretion)
• 3. Zinn 1993 van den Bergh 1993
  (CollapseAccretion)
• 4. Sagittarius dwarf, halo substructures, LCDM
  simulations...
• 5. Remaining question
• Where are the building blocks predicted by
  LCDM?
• ? Missing satellites problem (Moore99
  Klypin99)
• ? Early reionization could alleviate part of
  the problem (Bullock00)
• ? But stellar halo bulge are there
• dSphs appear to have little to do with
  halo formation (e.g., a/Fe).
• Where are the relics of building blocks
  that formed the Galaxy?

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CTIO 0.9m 760 frames!Lee, Rey, Sohn et al.
1999, Nature, 402, 55First good evidence for
the multiple populations in GC.(early hint
Norris96)
Clues from the Multiple Populations in w Cen
Discovery Paper! 130,000 stars
VLT 8.2m 30 frames Sollimar, Ferraro et al.
2005 (see also Pancino2000)
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Super-He-rich Subpopulations in w
CentauriEvidence from MS New Y2 Isochrones
Model Lee et al. 2005
Observation Bedin et al. 2004
See also Norris 04 Piotto05 Sollima06
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Super-He-rich Subpopulations in w
CentauriEvidence from Extended HB
Observation Ferraro et al. 2004
Model Lee et al. 2005
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Super-He-rich Subpopulations in NGC 2808Evidence
from Extended HB MS
(Piotto02)
Piotto07 HST/ACS
Lee05 Prediction EHB is a strong signature of
the presence of multiple populations in a GC!
HB is much more sensitive to any paramater
variation in GC! (see also DAntona05)
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1. Ejecta from Stars(1) AGB stars of
4-6M? (DAntona Caloi 04)(2) Wind from very
massive rotating stars (Maeder Meynet 06)(3)
Mini SNe (Piotto et al. 05)(4) First stars (Choi
Yi 07)? Significant fraction of He-enriched
subpopulation ( 25, w Cen NGC 2808) is not
reproduced from the yields of 1st generation!
(Bekki Norris 06 Karakas06 Choi Yi 07
Romano07)2. Gravitational Sedimentation of He
in Mini halos Diffusion time-scale can fall
below 108 yrs in mini halos dominated by DM until
the end of reionization (z 6) (Chuzhoy 06) ?
Consistent with many observations (e.g., NGC
2808), including radial gradient of extreme HB
blue MS! (Rey04 Sollimar06 Milone07 see
also Bekki Norris 06)
Where does the Helium come from?
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Direct Evidence for the Multiple Populations in
EHB Globular Clusters

• w Cen Lee99, Bedin04 (early hint Norris96)
• M54 (Sagittarius dwarf) Sarajedini Layden 95
• NGC 2808 Piotto07 Lee05 DAntona05
• NGC 1851 Milone07 (double subgiant branch)
• NGC 6388 Piotto 08 (double subgiant branch)
• HST/ACS survey (Piotto06 at Venice conference)
• Out of 59 GCs in their survey, 27 (mostly
  EHB GCs) show clear evidence of double MS or
  broadened MS !!
• ? Working hypothesis GCs with EHB as remaining
  cores of disrupted building blocks (dwarfs,
  subsystems, mini halos)?
• 1. Survey of 114 GCs with good CMDs suggests 28
  (25) have EHB!
• 2. LF, kinematics, MDF other properties of EHB
  GCs?

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Classification of GCs with EHB(CMD from
Piotto02 Y.-W. Lees compilation with H.-Y.
Lee)
25 (28/114) of Milky Way GCs have Extended HB
(EHB)!

• Normal HB

Strongly EHB (?VHB 3.5 )
Moderately EHB (3.0
?VHB
(?(B-V)HB0.78 with clear color bimodality)
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Extended HB (EHB) GCs are more massive than
normal GCs! (Lee, Gim Casetti-Dinescu 2007,
ApJ, 661, L49)
Early hints Fusi Pecci1993 Ree2002 Recio-Blanco
2006 NB. 1. Inferred mass of EHB GCs is
comparable to low-luminosity dwarf galaxies. 2.
Most GCs belonging to dwarf satellite galaxies
are fainter than Mv - 8 (MackeyvdB 04) have
no EHB! ? EHB GCs might have a unique origin?
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Full Spatial Motions Orbital Parameters for 55
GCs from Dinescu1999, 2003, 2007
OH GCs only (most of them are in the inner halo)
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Monte-Carlo Simulations Occurrence of this by
random selection
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Lee, Gim Casetti-Dinescu 2007, ApJ, 661, L49
EHB GCs r -0.02 to -0.31, p-values 0.25 to
0.95 Normal OH (P) r -0.71 to -0.95, p-values
0.000003 to 0.01 (except Lz, r 0.17 p-value
0.59),
excluding N6528 in panels (d) (e)

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• Kinematics of GCs with w/o EHB
• 1. Spatial motion of EHB GCs is dominated by
  random motion with no correlation between
  kinematics and metallicity.
• 2. However, most normal GCs in the inner halo
  (OH) show clear correlations between kinematics
  and metallicity, which is consistent with the
  ELS-like dissipational collapse.

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Metallicity Distribution Function
Rgc
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M/L ratio of EHB GCs appears distinct from normal
GCs
J. H. Yoon2008, in preparation Data from
Mandushev91, Mass from sv rc
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EHB GCs are distinct from normal GCs in

• 1. Mass
• 2. Kinematics
• 3. Metallicity distribution function
• 4. Mass-to-luminosity ratio?
• 5. Presence of multiple populations
  (super-He-rich subpopulations)
• ? Relics of primordial building blocks!

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ConclusionMW Formation Merger, Collapse,
Accretion

• Present-day Galactic GCs are ensemble of
  heterogeneous objects originated from three
  distinct phases of the Milky Way formation!
• (1) EHB GCs remaining cores or relics of first
  building blocks that assembled to form the
  nucleus and halo of the proto-Galaxy
• (2) OHD/B GCs with normal HB genuine GCs formed
  in the dissipational collapse of a transient
  gas-rich inner halo system that eventually formed
  the Galactic disk (ELS 1962)
• (3) YH GCs with normal HB genuine GCs formed in
  the outskirts of outlying building blocks that
  later accreted to the outer halo of the Milky Way
  (Searle Zinn 1978)

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GMT Multi-Object Spectroscopy of MS stars in EHB
Globular Clusters
8.2m VLT FLAMES Spectroscopy Blue MS is more
metal-rich! ? Implies super Y-rich (Piotto et
al. 2005) Intermediate resolution spectra 20-21
mag with 8.2m 12hrs/cluster ? 23-25 mag with
GMT
w Cen
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GMT MOS for the detection of EHB GCs in Fornax
gEs
NGC 1399 (CTIO 4m, Kim08)
SUBARU 10hrs Exp. (Kim08, in prep.) Bright GCs
(V 25
Origin of Color Bimodality of Globular Cluster
Systems of gEs

• Simple projection effect, rather than true
  metallicity bimodality! (Yoon, Yi, Lee 2006,
  Science)
• ? No significant age spread (Dt Es with GC color bimodality (80 MBmost massive Es completed at early Universe!

Bruzual Charlot 03
Data Peng06
Our Models
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GMT NIR AO Imager Photometry of bright RGB stars
in globular clusters in Fornax gEs
If diffraction limited, reliable photometry might
be possible to 1-3 mags below RGB tip at
Fornax/Virgo distances (Tolstoy 2006 GMT Science
Case Nov. 2006). (1) Measurement of global
metallicity from NIR RGB color, such as J-K. (2)
Discovery of multiple RGBs, if any (w
Cen-like)? (3) distance, etc