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