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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
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