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The Galactic Centera laboratory for testing physical processes near massive black holes
Reinhard Genzel, Frank Eisenhauer & Stefan Gilllessen, MPE
Radio Source 3C 273
The GC Legacy Program: Motivation
an unambiguous ‘proof ’ for the existence of a black hole requires the determination of the gravitational field/space time metric to the
scale of the event horizon.
1 light year ( 8” )1 light year ( 8” )
The GC Legacy Program: high resolution imaging & precision astrometry of stars
(as tracers of gravity)at 8 kpc:, 1mas=1 lh, 1mas/yr = 39 km/s
year
1990 2000 2010 2020
0.2”
20mas
2mas
300µas103
AstrometricPrecision
10µas
in Stuttgart
As seen from Munich
in San Francisco
on the MoonCurrent status (after 60 NTT and 170 VLT nights): 104 proper motions, 103.5 radial velocities/spectra, 47 individual orbits
CRIRES
FAST (1990)
SHARP(1991)
ESO NTT
NACO (MPIA & MPE)(2001)
3D(1993)
SINFONI(MPE + ASTRON)(2004)
PARSEC(MPE+MPIA+ESO)(2007)
GRAVITY(MPE+ESO +Grenoble + Paris +Cologne +Porto+MPIA_ (2015)
ESO VLT(I)APEX
The MPE-ESO Galactic Center Legacy Program
0
10
20
1990 1995 2000 2005 2010 20151
10
100
1000
47 orbits25 orbits6 orbits
G2peri
cusp
large velocitydispersion of nuclearcluster
top heavyIMF
HeI stars
IR flares
G2discovery
O star disks
firstNTT images
proper motions
S2 orbit
year
refereed publications per year
citations of top papers
Citations of top papers
Ref
eree
d pa
pers
per
yea
r 1000
100
NTT-SHARP/3D-2.2 LP1GTO LP2 Monitoring program
year
VISIR
0.05 0.025 0 -0.025 -0.05 -0.075
0.05
0.025
0
0.025
0.05
0.075
0.15
0.125
0.15
0.175
0.1
R.A. H''L
DecH''L
Highlights of the Galactic Center Legacy Program
2 lightdays
SgrA*
S2
1 lightweek
1 light year
0
20
40
60
80
100
250 300 350 400 450
3.6
8.6
13.6
18.6
23.6
28.6
33.6
38.6
43.6
48.6
53.6
58.6
63.6
68.6
time after UT 0:0:0 on Apr 4, 2007 (minutes)
3.8 µm dereddened flux density (mJy)
X-ray count rate (s-1)
1 hour IR
X
old
young
all
B-W
radius (1 light year)
Σ
• Compelling Detection of 4x106 M8 Central Mass, which must be a Schwarzschild-Kerr Black Hole, if GR is applicable
• ‘Paradox of Youth’: presence of a compact cluster of B/A-stars immediately around the MBH, as well as one or two rotating disks of O/WR stars surrounding it, indicating that episodic star formation and/or fast loss-cone injection/capture is effective near the MBH; the O/WR disk(s) have a top-heavy IMF
• No Bahcall-Wolf cusp: nature or nurture?• G2: tidal disruption of gas cloud/envelope in front of our eyes• ‘feeble’ emission and lack of ‘Big Blue Bump’ from MBH
(ηEdd~10-8 : advection dominated accretion & outflows)• IR/X- flares from inner accretion zone of MBH: synchrotron
emission from accelerated (γ~103) electrons at ~10 RS: magnetic reconnection events?
velocity
tim
e/po
siti
on
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]
Synchrotronmodel
IC model
SSCmodel
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-‐raysnearinfraredmid-‐
infrared
subm
m
mm
cm Synchtron
InverseCompton
Brems-‐strahlung
Nonthermalelectrons
no IR-UVbump
Photon energy
0.05 0.025 0 -0.025 -0.05 -0.075
0.05
0.025
0
0.025
0.05
0.075
0.15
0.125
0.15
0.175
0.1
R.A. H''L
DecH''L
stellar orbits testing the potential: S2
1992
2002/2018
2001SgrA*
MPE-VLTUCLA-Keck
S2/S02P=15.9 yRperi=1400 RS
(17 lh)βperi=0.03
Schödel et al. 2002, 2003, Ghez et al. 2003, 2008, Eisenhauer et al. 2003, 2005, Gillessen et al. 2009a,b, Meyer et al. 2012, Chatzopoulos et al. 2015, Fritz et al. 2015, Plewa et al. 2015
M�= 4.26(±0.14)stat(±0.2)sys x106 M8
R0= 8.36 (±0.1)stat(±0.15)sys kpcρ�>1016..19.5 M8pc-3
Mextended/M�< a few 10-2
M� & SgrA* coincident <0.3mas
S2-orbit
Cluster
Inward boundGRAVITY & submm-‐VLBI
pulsars?
1
2
3
4
5
β2 effects in radial velocities
relativisticprograde precession
spin fromFlares, L-‐T precession
Strong curvature:photon orbit
Quadrupole moment of metric, no hair & quantum effects
residuals of S2 data-‐Newtonvs. GR
GRAVITY(first years)
2
3S2: ~ 12 '1
SS
Re aπ ⎛ ⎞ΔΦ = ⎜ ⎟− ⎝ ⎠
‘shadow’
0.5”(1 light month)
Impact of GC Legacy Program
• Driver of State of the Art Instrumentation Development: FAST, SHARP, 3D, NACO, SINFONI, PARSEC, LABOCA, KMOS, GRAVITY
• Education: 29 PhDs, 25 postdocs Europe-wide • Papers: ~100 refereed publications , ~11,000 citations
• Remarkable String of (Theoretically) Unexpected Discoveries over 25 Years• A Highlight Result of ESO, in head-to-head competition with Keck
• GC as a Physics Laboratory: currently best proof of MBH paradigm: next step PN and strong-curvature tests of GR
• GC as an Astrophysics Laboratory: gas accretion, star formation and dynamics/structure/evolution of star cluster near MBH
: measuring R0 to percent accuracy: guidance on MBH accretion in low-density limit: strong participation & stimulation of theory