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Star Clusters in the
Galactic Center
Donald F. Figer
STScI
Sgr A* at 30 Workshop
Green Bank W.Va
March 25, 26, 2004
Collaborators
Massive Stars
Paco Najarro, CSIC
Tom Geballe, Gemini
Rolf Kudritzki, UH
IMF
Andrea Stolte, UF
Pavel Kroupa, U. Kiel
Carsten Weidner, U. Kiel
Stellar Velocities
Mark Morris, UCLA
Eric Becklin, UCLA
Ian McLean, UCLA
Cluster Dynamics
Sungsoo Kim, KHU
Star Formation History in GC
Mike Rich, UCLA
Gene Serabyn, JPL
Science Questions
•
•
•
•
•
•
•
•
•
What is the most massive star that can form?
Is the IMF universal?
What is the evolutionary sequence for massive stars?
What causes massive stars to "erupt"?
What is the star formation history of the Galactic
Center?
How do super-star clusters form?
How do super-star clusters affect their environments?
What is the dynamical evolution of massive clusters?
What is the connection between nuclear star formation
and massive central black holes?
GC Young Star Geography
60 pc
20 cm
N
E
Yusef-Zadeh, Morris, Chance 1984; Lang, Morris, Echevarria 1999
Galactic Center: Extinction
K band
60 pc
V band
N
E
Digitized Sky Survey
Figer 1995
Galactic Center Clusters
N
1 pc
E
Pistol Star
Central
Cluster
Quintuplet Cluster
Arches
Cluster
The Central Cluster
Schoedel et al. 2002; Genzel et al. 2003
Central cluster: Massive Stars
Genzel et al. 2000; Krabbe et al. 1991, 1995
Central cluster: High Resolution Spectra
Figer et al. 2004, in prep.
Central cluster: Radial Velocities
Figer et al. 2003
Radial Velocity Project
Radial Velocity Project
Arches Cluster
Lick 3-m
Figer 1995, PhD Thesis
Arches Cluster
Keck I 10-m
Serabyn, Shupe, & Figer
Nature 1998, 394, 448
Arches Cluster
HST/NICMOS
Figer et al. 1999, ApJ. 525, 750
Arches Cluster
VLT NAOS/CONICA
Stolte, A. 2003, PhD Thesis, University of Heidelberg
19” = 0.75 pc
Arches Cluster: P-alpha
see also:
Nagata et al.1995
Cotera et al.1996
Blum et al. 2001
Figer et al. 2002, ApJ, 581, 258
NIII
NIII
HeII
HeI/HI
NIII
HeI
HeI
Arches stars: WN9 stars
Figer et al. 2002, ApJ, 581, 258
Arches stars: O stars
HI
HeI
68
27
Figer et al. 2002, ApJ, 581, 258
Arches Cluster Mass Function
HST/NICMOS
VLT/NAOS/CONICA
Stolte et al. 2002
Arches Cluster: Mass Segregation
Figer et al. 1999, ApJ, 525, 750
Arches Cluster: Upper Mass Cutoff
Evidence for an
upper mass
cutoff to the
IMF
1000 M!
>20 stars
Figer 2003, IAU 212
Quintuplet cluster
Quintuplet cluster: Massive Stars
Figer, Najarro, & Kudritzki 2004, in prep.
Quintuplet-proper Members: DWCLs?
L~104.6 L
T~700 K
R~250 AU
WR Movie from Monnier, Tuthill, & Danchi 2002, ApJ, 567, L137
WC stars
Figer et al. 1999, ApJ, 525, 759
Pistol Star: Estimating the Luminosity
• Observing on the
Rayleigh-Jeans tail:
Can we guess the
animal by observing
its tail?
+l
1 um
Pistol Star: Estimating the Luminosity
+l
Beware!
1 um
Pistol Star: Spectrum
Figer et al. 1999, ApJ, 525, 759
Pistol Star: Mass
JHKLMN
+
D.M.
+
temperature
Lum.
+
model
2 Myr
Lum.
Mass
tracks by Langer
Figer et al. 1998, ApJ, 506, 384
LBVs in the Quintuplet
• Both the Pistol Star and FMM362 are
Luminous, Blue, and Variable
Pistol Star
FMM362
Figer et al. 1999, ApJ, 525, 759
Geballe et al. 2000, ApJ, 530, 97
LBV 1806-20
• Claim
• 1-7 LPistol
• 150-1000 Msun
• Primary uncertainties
• distance
• temperature
• singularity
• Figer, Najarro, Kudritzki
• in prep
• R=22000 1.5-4.2 um
• NIRSPEC/Keck
LBV 1806-20 is a binary?
Figer, Najarro, Kudritzki 2004, in prep.
Massive Stars in GC
Quintuplet
Arches
Center
Other
Total
Galaxy
red is estimate
WC
11
0
15
2
28
101
WN
LBV
5
6
15
2
28
2
0
5
0
7
O
100
160
100
?
360
134
13
?
RSG
1
0
2
?
3
?
Star Formation History in the GC
Figer et al. 2004, ApJ, 601, 319
Conclusions
• Massive GC clusters continuously likely form,
disperse, and populate the region.
• Most massive/compact young clusters in the Galaxy
are in the GC
• IMF is flat (at least in one cluster), and upper mass
cutoff might be observed
• The Pistol Star and FMM362 are amongst the most
massive stars in the Galaxy