NEAR HORIZON EFFECTS
Avery E. Broderick
EHT Collaboration
Sheperd Doeleman (MIT Haystack)
Vincent Fish (MIT Haystack)
Alan Rogers (MIT Haystack)
Ru-Sen Lu (MPIfR)
Michael D Johnson (CfA)
Dimitrios Psaltis (Arizona)
Tim Johannsen (UW-PI-CITA)
Avi Loeb (Harvard)
Carlos Wang (UW)
Elizabeth Griffin (UW)
Vancouver, Testing Gravity, 16.1.15
NEAR HORIZON EFFECTS:
HOW THE EVENT HORIZON TELESCOPE
IS ACCESSING GRAVITY VIA DIRECT IMAGING
Avery E. Broderick
EHT Collaboration
Sheperd Doeleman (MIT Haystack)
Vincent Fish (MIT Haystack)
Alan Rogers (MIT Haystack)
Ru-Sen Lu (MPIfR)
Michael D Johnson (CfA)
Dimitrios Psaltis (Arizona)
Tim Johannsen (UW-PI-CITA)
Avi Loeb (Harvard)
Carlos Wang (UW)
Elizabeth Griffin (UW)
Vancouver, Testing Gravity, 16.1.15
DIRECT IMAGING IS
EASIER SAID THAN DONE …
Galactic
Center
(Sgr A*)
Vancouver, Testing Gravity, 16.1.15
Very Long
Baseline Array
• Earth-sized mm VLBI array
http://www.eventhorizontelescope.org/
Haystack
CARMA
SMA,
JCMT
• Existing telescopes.
• Resolutions of ~𝟏𝟎 𝝁𝒂𝒔
ARO-SMT
IRAM
30m
LMT
APEX,
ASTE,
ALMA
APEX,
ASTE,
ALMA
SPT
SPT
Vancouver, Testing Gravity, 16.1.15
Plateau de
Bure
• Earth-sized mm VLBI array
http://www.eventhorizontelescope.org/
Haystack
CARMA
SMA,
JCMT
• Existing telescopes.
• Resolutions of ~𝟏𝟎 𝝁𝒂𝒔
ARO-SMT
IRAM
30m
LMT
•
•
•
•
•
Baselines 3  15
Closure phases 1  10 APEX,
ASTE,
SNRs improve x10
ALMA
Baseline lengths x2
Long EW and NW baseline!
APEX,
ASTE,
ALMA
SPT
SPT
Vancouver, Testing Gravity, 16.1.15
Plateau de
Bure
WHY MILLIMETER WAVELENGTHS?
Absorption in the source!
(Sgr A* & M87)
Optically thick
Scattering in …!
(Only Sgr A*)
Scattering
dominated
Optically
thin
Structure
dominated
+ applicability of radio techniques!
Vancouver, Testing Gravity, 16.1.15
RECONSTRUCTING IMAGES OF SGR A* (DISKS)
Interstellar
electron
cattering
Vancouver, Testing Gravity, 16.1.15
BSMEM image
reconstruction
Deconvolution of
the scattering
Fish et al. (2014)
RECONSTRUCTING IMAGES OF M87 (JETS)
7 stations BSMEM
Vancouver, Testing Gravity, 16.1.15
Lu et al. (2014)
PUBLISHED: “PROTO-EHT”
• 3 baselines
(2 long)
• Time ranges
from 10s-2yr
• Single data
type
Vancouver, Testing Gravity, 16.1.15
NOW: “PROTO-EHT”
• 5 baselines
(4 long)
• Time ranges
from 10s-7yr
• Many data
types
Vancouver, Testing Gravity, 16.1.15
VISIBILITIES
CARMA-SMT
1/53𝜇𝑎𝑠
V
𝑃ℓ(Jy)
𝐷~37.2 ± 0.5 𝜇𝑎𝑠
CARMA-JCMT
JCMT-SMT
6
Spatial frequency
−6 (10 /𝑟𝑎𝑑)
10 ℓ
Vancouver, Testing Gravity, 16.1.15
CLOSURE PHASES
Overlap
with
published
|V|’s
Statistically significant,
net positive CPs!
Ordered Phases
Courtesy of Vincent Fish
& EHT Collaboration
Random Phases
Vancouver, Testing Gravity, 16.1.15
POLARIZATION!
Vancouver, Testing Gravity, 16.1.15
𝑄 + 𝑖𝑈
𝑚=
𝐼
CONTEXT
Vancouver, Testing Gravity, 16.1.15
ANATOMY OF AN IMAGE
Vancouver, Testing Gravity, 16.1.15
ASTROPHYSICAL INPUTS
Dynamics
Magnetic Fields
Elizabeth Griffin
Thin disk
Thick disk
Carlos Wang
Plasma Distribution
Vancouver, Testing Gravity, 16.1.15
ASTROPHYSICAL MODELING
Misaligned disk?
J. McKinney
Dexter & Fragile (2013)
Tchekhovskoy et al.
Hot thick disk?
Vancouver, Testing Gravity, 16.1.15
Hot thin disk?
SPIN CONSTRAINTS
& EXPERIMENTAL VERIFICATION
Vancouver, Testing Gravity, 16.1.15
BUILDING CONFIDENCE: TESTING RIAFS
|V| Data
Closure Phase Data
Broad a priori
consistency!
Vancouver, Testing Gravity, 16.1.15
Courtesy of Vincent Fish &
EHT Collaboration
ORIENTING WITH THE ENVIRONMENT:
DISTRIBUTION OF STELLAR ANG. MOM.
Bartko et al. (2009)
Young stellar disks in
Galactic Center
See Psaltis et al. (2015)
Vancouver, Testing Gravity, 16.1.15
(90∘ −𝜉) in radians
LIMITS ON PRECESSION AND ITS CAUSES
Any precession at all
Aliasing
from 1 yr
Vancouver, Testing Gravity, 16.1.15
Lense-Thirring precession
Orbiting
S-Stars
FLARING DISK FEATURES
|V| Data
Closure Phase Data
On Day 94 of 2011
BUT!!
This was expected …
Vancouver, Testing Gravity, 16.1.15
Courtesy of Vincent Fish &
EHT Collaboration
MEASURING “MASS”
𝑀/𝐷
On horizon scales
Vancouver, Testing Gravity, 16.1.15
𝑀/𝐷1.8
On 3000x horizon scales
MEASURING “MASS” NOW
AND IN THE FUTURE
+TMT
Vancouver, Testing Gravity, 16.1.15
CONSTRAINING MONOPOLE HAIR
2
𝑑𝑠 = − 1 + 𝛼13
𝑀
𝑟
3
2𝑀
2𝑀
1−
𝑑𝑡 2 + 1 −
𝑟
𝑟
Johannsen (2013)
−1
2
2
2
2
2
𝑑𝑟 + 𝑟 𝑑𝜃 + 𝑟 sin 𝜃 1 + 𝛼13
𝑀
𝑟
3
𝑑𝜙 2
+TMT
Vancouver, Testing Gravity, 16.1.15
QUADRUPOLE HAIR:
LIMITS ON QUASI-KERR
𝐾
𝑔𝜇𝜈 = 𝑔𝜇𝜈
+ 𝜖ℎ𝜇𝜈
𝑀=𝑀
𝐽 = 𝑎𝑀
𝑄 = −𝑎2 𝑀 − 𝜖𝑀3
• Solution to vacuum Einstein equations when 𝒂 ≪ 𝑴
• Adds quadrupolar perturbation
(based on Hartle-Thorne metric for slowly spinning neutron stars!)
• No-hair theorems  Quasi-Kerr metric must be sick! It is inside 𝟐𝑴.
Vancouver, Testing Gravity, 16.1.15
LIMITS ON VIOLATIONS OF GR
IN JANUARY (|𝑉| THROUGH 2009)
Vancouver, Testing Gravity, 16.1.15
LIMITS ON VIOLATIONS OF GR
IN SEPTEMBER (+ CP THROUGH 2013)
Vancouver, Testing Gravity, 16.1.15
LIMITS ON VIOLATIONS OF GR
IN SINGLE NIGHT NEXT YEAR!
1% precision
strong-field tests
of GR imminent!
Vancouver, Testing Gravity, 16.1.15
ALMA
SPT
LMT
POSSIBILITIES FOR SPACETIME TOMOGRAPHY!
|V| Data
Closure Phase Data
On Day 94 of 2011
BUT!!
This was expected …
Vancouver, Testing Gravity, 16.1.15
Courtesy of Vincent Fish &
EHT Collaboration
COULD THIS BE A HOT SPOT?
YES!
But …
Vancouver, Testing Gravity, 16.1.15
CLOSURE PHASE VARIABILITY REVISITED!
f12
f31
f23
Expect ~5x better!
a = 0.9
Hot-spot at ~ 6M
Period = 27 min.
Vancouver, Testing Gravity, 16.1.15
Doeleman, Fish, A.E.B., Loeb & Rogers (2009)
TRACKING SPOTS WITH
POLARIZATION
cf. GRAVITY
Johnson et al. (2014)
Vancouver, Testing Gravity, 16.1.15
SUMMARY
• Sub-event horizon structure already detected
in astrophysical black holes
• EHT provides a heterogeneous data set, and is part of a
larger constellation of information about EHT sources
• While considerable astrophysical uncertainty remains, there are
many reasons to believe current accretion models of Sgr A*
• Gravity may be tested with the EHT via a number of avenues,
sub-percent precision tests of no hair theorems are imminent.
Vancouver, Testing Gravity, 16.1.15