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Taking a Radio Census of Binary Supermassive Black Holes
Taking a Radio Census of Binary Supermassive Black Holes
Sarah Burke SpolaorSwinburne University of Technology
CSIRO Astronomy and Space Sciences (ATNF)
Sarah Burke SpolaorSwinburne University of Technology
CSIRO Astronomy and Space Sciences (ATNF)
Stalling, inspirals, gravitational radiation, and SKAStalling, inspirals, gravitational radiation, and SKA
< 200 parsecsShape inner galaxyHigh velocity starsHelp mould fundamental relations with MBH?
< 200 parsecsShape inner galaxyHigh velocity starsHelp mould fundamental relations with MBH?
< 1 parsecGravitational waves: Pulsar timing arraysz < 2MBH > 106 M
< 1 parsecGravitational waves: Pulsar timing arraysz < 2MBH > 106 M
CoalescenceGravitational waves: LISAMBH < 107 M
CoalescenceGravitational waves: LISAMBH < 107 M
BH separation (pc)
Rel
ativ
e N
umbe
r of B
inar
ies
(per
z p
er M
BH)
0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5
Dynamical friction(efficient)
3-body stellar interactions?
Disk “ringing”?Gas drag?
GW emission inPulsar Timing band
Jaffe and Backer (2003):N α
a13/2
Binary SMBHforms
?
LISA: final inspiral and ringdown
N α
a?
BH separation (pc)0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5
“Stall”region?
Pre-GW stage: longer than a Hubble time?
DANGER!NO astrophysical gravitational wave
signals!
Merritt 2006
BUT!Plenty of visible stalled systems?
Rel
ativ
e N
umbe
r of B
inar
ies
(per
z p
er M
BH) less
efficient
0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5
GW emissionN α
a13/2
Dynamical friction?
Known small-orbit systemsKnown small-orbit systems
BH semi-maj. axisLISA: final inspiral and ringdown
3C75
NGC326
me™ and a) decompressorsee this picture.
NGC6240
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Rodriguezet al 2006
Rel
ativ
e #
Komossa et al. 2003
Owen et al. 1985 Owen et al. 1985
Optical gal/QSOdoubles; disturbed galactic structure
1 mas resolution
Long Baseline InterferometryLong Baseline Interferometrylin
ear s
cale
, pc
redshift
Stall radius
Binary forms
2 x108 Mbinary
Radio spectral mappingRadio spectral mapping
Exploit:Radio active galactic nucleus ≈ black holeUnique spectral energy distribution of compact radio nuclei --> (flat/peaking; α>-0.5 at GHz)Sub-mas radio resolution
Do:Spectral mapping at GHz frequenciesSearch for multiple flat-spectrum componentsAt interesting scales & masses!
Exploit:Radio active galactic nucleus ≈ black holeUnique spectral energy distribution of compact radio nuclei --> (flat/peaking; α>-0.5 at GHz)Sub-mas radio resolution
Do:Spectral mapping at GHz frequenciesSearch for multiple flat-spectrum componentsAt interesting scales & masses!
Direct Detection:Spatially Resolved Systems
log frequency
log
ampl
itude
log frequency
log
ampl
itude
DoubleAGN @7 parsecs!
GHz-peak spectrum:
unique to young, synchrotron cores
GHz-peak spectrum:unique to young, synchrotron cores
>1 GHz>1 GHz
0402+379Rodriguez et al. 2006
Spectral index, α
(S ~ f α)
Our searchOur search
>105 hrs archival VLBA data (Petrov et al.)
2, 5, 8, 15, 24, up to 43 GHz
3982 spectral images for 3114 active galactic nuclei (drawn from ~6000)
>105 hrs archival VLBA data (Petrov et al.)
2, 5, 8, 15, 24, up to 43 GHz
3982 spectral images for 3114 active galactic nuclei (drawn from ~6000)
Submitted to MNRAS;“A Radio Census of Binary Supermassive Black Holes”, Burke-Spolaor 2010
min
. res
olva
ble
scal
e (p
c) Binary formed
Stall radius
Pulsar band
ResultsResultsONE binary out of 3114! (Rodriguez source)
0.03% radio AGN visible as binary
0.15 < tinspiral < 1.5 Gyr (no stalling!)
ONE binary out of 3114! (Rodriguez source)
0.03% radio AGN visible as binary
0.15 < tinspiral < 1.5 Gyr (no stalling!)
Caveat:Covariance with probability of radio ignitionof second black hole: Pradio
Survey many sources!
The way forward?The way forward?
To find another:~3,000
To detect ~10:~30,000
To break Pradio - tinspiral degeneracy:~45,000 (and find no more)
To have far higher success rate:Have sensitivity << 40 mJy
To find another:~3,000
To detect ~10:~30,000
To break Pradio - tinspiral degeneracy:~45,000 (and find no more)
To have far higher success rate:Have sensitivity << 40 mJy
Method RequirementsMethod Requirements1.
Multi-frequency GHz
2. Long enough baselines
3. Image/flux fidelity
u, v coverageCalibration/variability
4. Need many sources
5. Few mJy sensitivity
1. Multi-frequency GHz
2. Long enough baselines
3. Image/flux fidelity
u, v coverageCalibration/variability
4. Need many sources
5. Few mJy sensitivity
Beamsize
Possible SKA design issue
SKA wins over VLBA
SKA BaselinesSKA Baselines
ν,ν, GHzGHzλ,λ,cmcm
θθ3000km3000km
, , masmas
linear res linear res at any z, at any z, DD3000km3000km
1 21 20 < 170 pc
2 15 10 < 85 pc5 6 4 < 35 pc8 3.7 2.5 < 20 pc
10 3 2 < 15 pc20 1.5 1 < 9 pc40 0.7 0.5 < 4 pc
At z < 0.1 At z < 0.1 At z < 0.2At z < 0.2 At z < 0.3At z < 0.3>> Earth >>>Earth Moon-ish
> Earth >>Earth >>Earth7,360 km >Earth > Earth4,600 km 8,250 km Too big
3680 km 6,600 km 9,000 km1840 km 3,300 km 4,470 km920 km 1,650 km 2,230 km
Minimum baseline to resolve astall Minimum baseline to resolve astall
ConclusionsConclusionsOnly direct way to find/probe small-orbit supermassive black hole binaries
Relevance: gravitational waves, galaxy formation, post-merger dynamical processes
<0.03% of radio AGN exhibit binariesNo evidence for widespread stalling
0.15 < tinsp < 1.5 Gyr
Need more sources, long baselines, adequate sensitivity, multi-frequency >GHz coverage
SKA will tell all! (?)
Only direct way to find/probe small-orbit supermassive black hole binaries
Relevance: gravitational waves, galaxy formation, post-merger dynamical processes
<0.03% of radio AGN exhibit binariesNo evidence for widespread stalling
0.15 < tinsp < 1.5 Gyr
Need more sources, long baselines, adequate sensitivity, multi-frequency >GHz coverage
SKA will tell all! (?)
(END)(END)
Merger rate predictionsMerger rate predictions
How long can the inspiral last before a positive detection?
Millennium Database: Springel et al. (2005)
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