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)