The Galactic Centersome recent highlights

Reinhard GenzelMPE & UCB Physics

see Genzel, Eisenhauer & Gillessen arXiv:1006.0064(Rev.Mod.Phys.)

a complete orbit: S2

1992

2002

2010

2001

Ghez et al. 2008, Gillessen et al. 2009a,b

SgrA*

M= 4.30(±0.20)stat(0.30)sys x106 M

R0= 8.28 (±0.15)stat(±0.29)sys kpc

Ghez et al. 2008, Gillessen et al. 2009 a,b

SgrA*

Backer & Sramek 1996, Menten et al. 1997, Bower et al. 2003, 2005, Reid & Brunthaler 2004, Shen et al. 2005, Baganoff et al. 2001, 2003, Aharonian et al. 2004-06, Bartko et al. 2007, Doeleman et al. 2008, Falcke, Melia & Algol 2000, Broderick & Loeb 2006, 2007, Fish et al. 2009

104

103

102

10

1

R/Rs

vpm 2 (2σ), 20 km/s expected Brownian motion: 0.2 km/s

Reid & Brunthaler 2004

θFWHM (1.3mm) =37 (+5,-3) μarcsec < θmin(lensing)

Avery Broderick’s

dream of the future

Milosavljevic & Hansen 2003, Mikkola & Merritt 2008, Gualandris & Merritt 2007, 2009, Gillessen et al. 2009a

could SgrA* be a binary ?

excluded

allowed

mass distribution of the nuclear cluster

Genzel et al. 1996, Haller et al. 1996, Trippe et al. 2008, Schödel et al. 2009, Freitag et al. 2006, Hopman & Alexander 2007, Beloborodov et al. 2006, Gillessen et al. 2009a,b, Ghez et al. 2008, Bartko et al. 2010

dynamical detection of stellar mass at 1pc and light allows a rangeof IMF and central concentrations

the exact numbers are important for LISA inspiral event rates and perturbation of S-star orbits

102

103

104

105

106

107

0.001 0.01 0.1 1 10

103 104 105 106 107

=1.75

2 limitnon-closureS2-orbit

MS

SBHNS

WD

SBH

MS

=1.8

=0

=1.3

CNDS-stars

old stars

Ro= 8.3 kpc

S2

clockwise disk

radius (parsec)

encl

osed

mas

s (s

olar

mas

ses)

R/Rs

-20

-10

0

10

20

-1001020

R.A.-offset from SgrA* (arcsec)

Dec

.-of

fset

from

Sgr

A*

(arc

sec)

Allen et al. 1990, Forrest et al. 1987, Krabbe et al. 1991, 1995, Gerhard 2001, Levin & Beloborodov 2003, Genzel et al. 2003, Kim et al. 2003, Portegies Zwart et al. 2003. 2004, Guerkan et al. 2005, Paumard et al. 2006, Martins et al. 2007, Alexander et al. 2007, Yu, Lu & Lin 2007, Lu et al. 2008, Bartko et al. 1009a , Hobbs & Nayakshin 2008, Bonnell & Rice 2008, Kocsis & Tremaine 2010

0

1

2.04 2.06 2.08 2.10 2.12 2.14 2.16 2.18 2.20

IRS16 SW (Ofpe/LBV)

wavelength (m)

-0.1

0

0.1

2.05 2.10 2.15 2.20 2.25 2.30 2.35 2.40

IRS16SE2 (WN5/6)

wavelength (m)

0.9

1.0

2.10 2.15 2.20

1 light year

The paradox of youth: young stars near the BH

~180 OB stars in the central parsec !

they can account for the entire FIR, UV and EUV luminosity of the Galactic Center and the excitation/ionization of the SgrA West

HII region

and exhibit ordered motion

Allen et al. 1990, Forrest et al. 1987, Krabbe et al. 1991, 1995, Gerhard 2001, Levin & Beloborodov 2003, Genzel et al. 2003, Kim et al. 2003, Portegies Zwart et al. 2003. 2004, Guerkan et al. 2005, Paumard et al. 2006, Martins et al. 2007, Alexander et al. 2007, Yu, Lu & Lin 2007, Lu et al. 2008, Bartko et al. 1009a , Hobbs & Nayakshin 2008, Bonnell & Rice 2008, Kocsis & Tremaine 2010

The paradox of youth: young stars near the BH

two warped & thick disks or a single, more complex structure ?

Top heavy IMF

Paumard et al. 2006, Bartko et al. 2010, Buchholz et al. 2009, Nayakshin & Sunyaev 2005

0.45 0.3/

< ~ 30

dN dm m

m M

PMF (KLF)= IMFfor young populationand at high mass end of continuous star formation

2.3

/

dN dm m

limits on A-stars in ‘deep’ fields

only believable case for significantly top heavy IMF ? (Bastian 2010)

Star formation history in central

parsec

Blum et al. 2003, Maness et al. 2007, Pfuhl et al. 2010, Löckmann et al. 2010

10-4

10-3

10-2

10-1

106 107 108 109 1010

Pfuhl 2010: =0.85Pfuhl 2010 red clump: =2.35 (m

l=2.35), R2.5pc

Blum 2003 bright giants: =2.35 (ml=0.7), R2.5pc

red supergiants: =-0.85, R2.5pcred supergiants: =-0.85, R1pc6 Myr star disk(s): =-0.85, R1 pc

look-back time t (yr)

star

form

atio

n ra

te (

Msu

n y

r-1)

103

104

105

106

107

106 107 108 109 1010

look-back time t (yr)

form

ed s

tars

(M

sun)

over ≥1pc and 10 Gyrs: IMF cannot have been as flat as in disk(s)

Genzel et al.1996, 2003, Eisenhauer et al. 2005, Schödel et al. 2007, Bartko et al. 2009b, Buchholz et al. 2009, Do et al. 2009, Dale et al. 2009, Merritt 2009, Dale et al. 2009, Davies 2010

is there a stellar cusp ?

the cusp consists mainly of relatively massive young stars; their lifetime is too short to be relaxed by two-body relaxation

the old stars do not exhibit a cusp

collisions? initial conditions ? top heavy IMF ? gouging by IMBH?

0.01

0.1

1

10

100

1 10

0.01 0.1 1

0.0001

0.001

0.01

0.1

1

late type stars K15.5 B-stars K

s16

B-stars K15.5O/WR-stars clockwiseK

s<12.5 AGB stars

amplitude of red clump in KLFall stars K

s17

distance from SgrA* (arcseconds)

stel

lar

surf

ace

dens

ity (

star

s ar

csec

-2)

ampl

itude

of r

ed c

lum

p in

KLF

distance (parsec)

S-stars

B

O/WR

AGB

late

red clumpdepth

1”(0.04 pc)

R ~ 1 light month

near-isotropic, random orientation (p=74%)

properties of cusp star orbits

Gillessen et al. 2009a

monitoring the orbits of the innermost 100 stars in the central light year; currently 35 orbits

thermaleccentricties ~2σ greater than thermal distribution

evidence for remnants

Muno et al. 2005

evidence for stellar remnant binaries from X-ray (radio) transients

how did the young stars get into the central pc ?

star disk(s)

central cusp

in situ star formation:tidally disrupted ‘dispersion ring’ of gas + gravitational instability in disk

+ -

external formation:transport by in-spiraling massive cluster (+ IMBH?)

- -

transport by scattering & relaxation:massive perturbers + Hills capture + resonant relaxationnear BH

-

+?Alexander, Merritt, Gerhard, Hills, Nayakshin, Levin, Bonnell, Tremaine, Morris, Portegies Zwart, Perets

hyper velocity stars

Brown et al. 2005, 2006, 2008, 2010, Hills 1989, Yu & Tremaine 2003

expected ejection rate 10-5 yr-1: ~103 HVs within 100 kpc

Emission from SgrA*

Baganoff et al. 2001, Genzel et al. 2003,, Ghez et al. 2004, 2005, Eisenhauer et al. 2005, Gillessen et al. 2006, Eckart et al. 2005, 2006a/b, 2008, Trippe et al. 2007, Meyer et al. 2007, Porquet et al. 2008, Marrone et al. 2008, Do et al. 2008, Yusef-Zadeh et al. 2008, 2010, Dodds-Eden et al. 2009, 2010, Sabha et al. 2010

L’-band VLT

XMM

1E+31

1E+32

1E+33

1E+34

1E+35

1E+36

1E+37

1E+08 1E+10 1E+12 1E+14 1E+16 1E+18 1E+20vL

v [e

rg/s

]

v [Hz]

Synchrotron model

IC model

SSC model

Steady state model

x 0.1x 1

x 10

x 0.01

1E+31

1E+32

1E+33

1E+34

1E+35

1E+36

1E+37

1E+08 1E+10 1E+12 1E+14 1E+16 1E+18 1E+20

vLv

[erg

/s]

v [Hz]

X-ra

ys

near

infr

aredm

id-

infr

ared

subm

m

mm

cm Synchtron

InverseCompton

Brems-strahlung

Nonthermalelectrons

Dodds-Eden et al. 2010:40 epochs 2004-2009

Do et al. 20096 epochs 2005-2007red power law PSD

prob

abili

ty o

f Flu

x(m

Jy)

0 4 8 12 16 20 dereddened Flux (mJy)

cumulative flux distribution

magnetic reconnection

Baganoff et al. 2001, Genzel et al. 2003,, Ghez et al. 2004, 2005, Eisenhauer et al. 2005, Gillessen et al. 2006, Eckart et al. 2005, 2006a/b, 2008, Trippe et al. 2007, Meyer et al. 2007, Porquet et al. 2008, Marrone et al. 2008, Sharma et al. 2007, Do et al. 2008, Dodds-Eden et al. 2010a,b,Yusef-Zadeh et al. 2006-2010, Markoff 2010, Melia & Falcke 2001

magnetic reconnection eventacceleration of electrons, drop in B-field

IR/X-synchrotron radiationadiabatic expansion

Dodds-Eden et al. 2010a

The potential of GC measurements for new

constraints on GR

S-star orbits

centralcusp

flares+submm

BH merger gravitational wave pattern

6 RS

Earth Orbit

RS ~ 10 µas

fiel

d cu

rvat

ure

Psaltis 2004

post-Newt. to β2

(grav.redshift,transv. Doppler)

radial & L-T precess.Q2=J2/M (no hair)

strong field effects:photon orbit….

Eisenhauer et al. 2008,Rubilar & Eckart 2001, Weinberg et al. 2005, Zucker et al. 2006, Will 2008, Merritt et al. 2010