Star Clusters in the Galactic Center

Sgr A* at 30 WorkshopGreen Bank W.Va

March 25, 26, 2004

Donald F. FigerSTScI

CollaboratorsMassive Stars

Paco Najarro, CSICTom Geballe, GeminiRolf Kudritzki, UH

IMFAndrea Stolte, UFPavel Kroupa, U. Kiel Carsten Weidner, U. Kiel

Stellar VelocitiesMark Morris, UCLAEric Becklin, UCLAIan McLean, UCLA

Cluster DynamicsSungsoo Kim, KHU

Star Formation History in GCMike Rich, UCLAGene 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

Yusef-Zadeh, Morris, Chance 1984; Lang, Morris, Echevarria 1999

20 cm

N

E

60 p

c

Galactic Center: ExtinctionK band

Figer 1995

V band

Digitized Sky Survey

60 p

c

N

E

Galactic Center Clusters

CentralCluster

N

E

Quintuplet Cluster

1 pc

Pistol StarArchesCluster

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

Lick 3-m Figer 1995, PhD Thesis

Arches Cluster

Keck I 10-m Serabyn, Shupe, & FigerNature 1998, 394, 448

Arches Cluster

HST/NICMOS Figer et al. 1999, ApJ. 525, 750

Arches Cluster

VLT NAOS/CONICAStolte, A. 2003, PhD Thesis, University of Heidelberg

Arches Cluster

Arches Cluster: P-alpha

19”

= 0

.75

pc

see also:

Nagata et al.1995Cotera et al.1996Blum et al. 2001

Figer et al. 2002, ApJ, 581, 258

Arches stars: WN9 stars

He

I

He

I

He

I/H

I

NII

I

He

II

NII

I

NII

I

Figer et al. 2002, ApJ, 581, 258

Arches stars: O stars

68

27

HI

HeI

Figer et al. 2002, ApJ, 581, 258

Arches Cluster Mass Function

Stolte et al. 2002

HST/NICMOS VLT/NAOS/CONICA

Arches Cluster: Mass Segregation

Figer et al. 1999, ApJ, 525, 750

Arches Cluster: Upper Mass Cutoff

Figer 2003, IAU 212

1000 M!

Evidence for an upper masscutoff to the IMF

>20 stars

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

Figer et al. 1999, ApJ, 525, 759

WC stars

• Observing on the Rayleigh-Jeans tail:

Can we guess the animal by observing its tail?

Pistol Star: Estimating the Luminosity

1 um+

Beware!

Pistol Star: Estimating the Luminosity

1 um+

Figer et al. 1999, ApJ, 525, 759

Pistol Star: Spectrum

Pistol Star: Mass

JHKLMN+

D.M.+

temperature

Lum.

Lum.+

modelMass

tracks by Langer

Figer et al. 1998, ApJ, 506, 384

2 Myr

Figer et al. 1999, ApJ, 525, 759

LBVs in the Quintuplet

Geballe et al. 2000, ApJ, 530, 97

FMM362

• Both the Pistol Star and FMM362 are Luminous, Blue, and Variable

Pistol Star

• 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

Figer, Najarro, Kudritzki 2004, in prep.

LBV 1806-20 is a binary?

Massive Stars in GC

WC WN LBV O RSG

Quintuplet 11 5 2 100 1Arches 0 6 0 160 0Center 15 15 5 100 2Other 2 2 0 ? ?Total 28 28 7 360 3

Galaxy 101 134 13 ? ?

red is estimate

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