The Event Horizon Telescope:
Observing Black Holes with
Schwarzschild Radius Resolution
Sheperd Doeleman
MIT Haystack Observatory
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Centaurus A: Radio
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AGN Taxonomy
Urry & Padovani 1995
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How we view AGN/Jets
M87: Walker et al 2009
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Strong GR Effects:
• The black hole ‘shadow’ (Bardeen 1973; Falcke,
Agol, Melia 2000; Johannsen & Psaltis 2010)
Spinning (a=1)
Non-spinning (a=0)
Dsh = 9/2 * Rsch
Dsh = sqrt(27) * Rsch
• Measuring the shadow gives Mass.
• (Johannsen, Psaltis et al 2012).
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Strong GR Effects:
The Innermost Stable Circular Orbit Stable Circular Orbit Size.
• Innermost
• Maximally‐spinning • Maximally‐spinning • Non‐spinning BH. prograde BH (spinning in same direction as disk). • Accretion disk still rotates! retrograde BH (spinning in opposite direction as disk). • ISCO at 6 GM/c2. • ISCO at 9 GM/c2. • No frame‐dragging: orbits cease to spiral in and instead plunge toward BH inside ISCO. • Frame‐dragging acts in opposition to disk angular momentum, 6
causing orbits to plunge farther out. • ISCO at 1 GM/c2. • Frame‐dragging rotationally supports orbits close to BH. From a talk by Laura Brenneman
© Sky & Telescope, May 2011
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SgrA*: Best Case for a SMBH
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SgrA*: Best Case for a SMBH
• Stellar orbits approaching within 45 AU.
Ghez et al
Genzel et al
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SgrA*: Best Case for a SMBH
• Stellar orbits approaching within 45 AU.
• Short time scale X-ray flares (300 sec rise).
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Short Wavelength VLBI
Resolution:
λ/D (cm) ~ 0.5 mas
λ/D (1.3mm) ~ 30 µas
λ/D (0.8mm) ~ 20 µas
ISM Scattering:
Θscat ~ λ2
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1.3mmλ Observations of SgrA*
90
8k
m
m
k
30
40
m
0k
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2
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Builds on long history of SgrA* VLBI and mmVLBI.
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Determining the size of SgrA*
About 4 Schwarzschild
radii across.
SMT-CARMA
JCMT-CARMA
Evidence for the
existence of an Event
Horizon.
SMT-JCMT
ρ = 10 M  pc
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−3
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Tighter Constraints on BH using
RIAF models of SgrA*.
Broderick, Fish, Doeleman & Loeb 2011
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VLBA Movie of M87 @ 43 GHz (7 mm)
Craig Walker et al. 2008
6.6x109 Solar Mass BH at 16 Mpc
Beam: 0.43x0.21 mas
0.2mas = 0.016pc = 60Rs
1mas/yr = 0.25c
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VLBA Movie of M87 @ 43 GHz (7 mm)
Craig Walker et al. 2008
6.6x109 Solar Mass BH at 16 Mpc
Beam: 0.43x0.21 mas
0.2mas = 0.016pc = 60Rs
1mas/yr = 0.25c
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Relativistic
Jets
Magnetically driven jet launching ?
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Location of M87’s SMBH
Hada et al, Nature, 2011
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M87: the Jet Base Size
5.5 Rsch
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Strong GR Effects: M87 Jet
• Smaller than the lensed ISCO: prograde disk.
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SgrA*’s view of the EHT
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SgrA*’s view of the EHT
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SgrA*’s view of the EHT
LMT
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SgrA*’s view of the EHT
IRAM
LMT
ALMA
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SgrA*’s view of the EHT
IRAM
LMT
ALMA
SPole
SPole
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SgrA*’s view of the EHT
GLT - Greenland
IRAM
LMT
ALMA
SPole
SPole
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Phasing ALMA
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•
•
Single most important objective for EHT.
Increases resolution by x2, sensitivity by x10.
First ALMA VLBI scheduled 2014.
Builds on
work by
Weintroub
et al at CfA
on phased
array
processors.
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Phasing ALMA
•
•
•
Single most important objective for EHT.
Increases resolution by x2, sensitivity by x10.
First ALMA VLBI scheduled 2014.
Builds on
work by
Weintroub
et al at CfA
on phased
array
processors.
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Fringes to APEX: from SMA, SMT
9450km
baseline from
APEX-SMA
28 micro asec
MPIfR, Onsala, SMA, SMT, Haystack
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512Mb/s VLBI System
Analog Filter Backend
Tape Recorder
• Total cost $1 Million to equip a VLBI station
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New 4Gb/s VLBI System
Digital Backend (DBE)
Digital Recorder (Mark5)
• Total cost $75K per station.
• X8 improvement in BW: factor of x2.8 in
sensitivity.
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16 Gb/s VLBI Backends
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Prototype Mark6: 16Gb/s
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Robust 1.3mm VLBI Closure Phases
on quasar 1924-292
Rusen Lu et al 2012
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LMT: Improving RIAF models
through closure phases.
Broderick et al 2011
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The Importance of Phase
Oppenheim
& Lim
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Progression to an Image: M87
Baron & Monnier (U. Michigan)
GR Model
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De
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Br
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Progression to an Image: M87
Baron & Monnier (U. Michigan)
GR Model
4 Stations
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De
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Br
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Progression to an Image: M87
Baron & Monnier (U. Michigan)
GR Model
4 Stations
7 Stations
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Tracing Black Hole Orbits with VLBI
Jeremy Steeger et al
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Preliminary EHT Polarization Results
Fish et al 2009
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South Pole:
Polarization Signatures at the Event Horizon:
Orbiting hot-spot
Quiescent Structure
Fish et al 2009
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GRMHD Simulation of SgrA*
Dolence, Gammie
et al
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EHT Roadmap
• LoI to be signed by participants in late Sept.
• ALMA Phasing submission to ADSC this month
(anticipated ALMA Board approval Nov).
• VLBI @ LMT soon at 3mm (SgrA* parallax).
• Greenland Tel. plans underway (NSF proposal).
• Fringe test with APEX carried out in May.
• Full dual pol 1.3mm VLBI in March.
• NSF SPole proposal awarded (with Ariz & Chic)
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Technical Milestones
• Wideband phased array processors & enable dual
sideband extraction.
• Upgrade JCMT Rx: x2 in Tsys and wideband.
• Test and deploy new VLBI DBE’s & Recorders.
• Modify VLBI correlator (DiFX) code and build
full EHT cluster.
• Experiment with WVR’s for atmospheric phase
correction.
• Procure media - eventual move to solid state.
• Tests at 0.8mm.
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Event Horizon Telescope Collaboration
MIT Haystack: Shep Doeleman, Alan Rogers, Vincent Fish, et al
NAOJ: Mareki Honma, Tomoaki Oyama, Kazunori Akiyama
U. Arizona Steward Obs: Lucy Ziurys, Robert Freund, Dan Marrone
Harvard CfA: Jonathan Weintroub, Jim Moran, Ray Blundell, et al
CARMA: Dick Plambeck, Mel Wright, David Woody, Geoff Bower
NRAO: John Webber, Ray Escoffier, Rich Lacasse
Caltech Submillimeter Observatory: Richard Chamberlin
UC Berkeley SSL: Dan Werthimer
MPIfR: Thomas Krichbaum, Anton Zensus, Alan Roy, et al
IRAM: Michael Bremer, Karl Schuster
APEX: Karl Menten, Michael Lindqvist
James Clerk Maxwell Telescope: Remo Tilanus, Per Friberg
ASIAA: Paul Ho, Makoto Inoue, Keiichi Asada
U. Concepcion: Neil Nagar
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Summary
• 1.3mm VLBI confirms Rsch scale structure in
M87 and SgrA*.
• International collaboration forming strong EHT
organization.
• Key technical advances underway and roadmap
to full EHT by 2015 clear.
• Most effort low risk: greatest risk is funding.
• EHT is opening a new window on BH study.
• GLT is key new element to the EHT.
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M87: Measuring the ISCO
Prograde
No Spin
Retrograde
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