Pulsar Timing and Galaxy EvolutionPulsar Timing and Galaxy Evolution

Sarah BurkeSwinburne University/ATNF

ATNF GW MtgDecember 12, 2008

Sarah BurkeSwinburne University/ATNF

ATNF GW MtgDecember 12, 2008

Common Ground in the GWBCommon Ground in the GWB

Supervisors:Matthew Bailes,David Barnes,Simon Johnston,Dick Manchester

In collaboration with:Dick Manchester,Ron Ekers,Chris Phillips

CLAIMCLAIMPulsar timing should detect GW emission

from binary supermassive black hole (SMBH) systems at sub-pc separations

Supermassive: mBH > ~106 MSun

GW detection from PTingGW detection from PTing

GWB A background of emission

from hard binaries Supermassive systems

with BH mass ratio >0.3 Porb = 106 - 108 s Contributing population

anywhere from z = 0 to high redshift (z > 6)

GWB A background of emission

from hard binaries Supermassive systems

with BH mass ratio >0.3 Porb = 106 - 108 s Contributing population

anywhere from z = 0 to high redshift (z > 6)

Single source Nearby (z<1) Porb = 106 - 109 s Very close orbital

separation; a < ~0.1 pc

Single source Nearby (z<1) Porb = 106 - 109 s Very close orbital

separation; a < ~0.1 pc

All binary black holes must have been formed via a galaxy merger and undergo subsequent inspiral processes before reaching the pulsar regime.

The modelling approachThe modelling approach

1. How many merged galaxies exist?- How many galaxies containing SMBHs are merging?- What is the BH mass function?- When/where in the universe did the merger happen?

2. What is the timescale for inspiral, coalescence of a resulting SMBH binary?

1. How many merged galaxies exist?- How many galaxies containing SMBHs are merging?- What is the BH mass function?- When/where in the universe did the merger happen?

2. What is the timescale for inspiral, coalescence of a resulting SMBH binary?

Stochastic GWB SourcesStochastic GWB Sources

Gravitational wave frequency

Cha

ract

eris

tic S

trai

n

A long way to go!A long way to go!

“Last parsec” problem is still unresolved!

Binary SMBH populations unknown Even at earlier stages of binary evolution

Hierarchical models vs. Monolithic

No local binary black holes to test GR theory and pulsar timing methods.

“Last parsec” problem is still unresolved!

Binary SMBH populations unknown Even at earlier stages of binary evolution

Hierarchical models vs. Monolithic

No local binary black holes to test GR theory and pulsar timing methods.

CLAIMCLAIMIdentification of SMBH binary systems in local galaxies will be beneficial to pulsar

timers and galaxy evolutionists

Thus far, all binary evidence has been tenuous and (nearly) all claims for binaries have been

indirect

Binary Detection MethodsBinary Detection Methods

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Etcetera

A robust, direct binary BH detection method

A robust, direct binary BH detection method

Exploitation: Unique spectral energy distribution of AGN Relation of AGN to BHs (Ron’s talk) Existence of double, compact flat/inverted

spectrum sources not yet explored

Combined with: High-frequency selection favours AGN

(AT20G) Good LBA resolution (~1 mas)

Exploitation: Unique spectral energy distribution of AGN Relation of AGN to BHs (Ron’s talk) Existence of double, compact flat/inverted

spectrum sources not yet explored

Combined with: High-frequency selection favours AGN

(AT20G) Good LBA resolution (~1 mas)

Direct Detection:Spatially Resolved Systems

0402+379Rodriguez et al. 2006

log frequency

log

ampl

itude

log frequency

log

ampl

itude

Doublenucleus

VLBI

Parameter spaceParameter spaceN

umbe

r

0 1 10 100 1000 1e4 1e5 1e6 1e7 1e8 --->

AT20G

CLASS

2-pointcorrelations

Galaxy merger rates

Chance radio, xray double detections

Pulsar timingsensitivity

Integrated over redshift bin and BH mass range

Linear separation between most massive galactic BHs (pc)

Parameter spaceParameter space

Linear separation between most massive galactic BHs (pc)

Num

ber

0 1 10 100 1000 1e4 1e5 1e6 1e7 1e8 --->

Integrated over redshift bin and BH mass range

Bou

nd, m

ergi

ng

gala

xies

/hal

os

Massive objects

falling to centre;

dynamical friction

Bound binaryBH systems

Galaxy groups, large scale clustering, chance projeted separations

Where things get interestingWhere things get interesting

BH separation

Num

ber

0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5

Dynamical friction

3-body interactionswith stellar background

BinaryhardeningGW emission;

final inspiralJaffe and Backer (2003):N a13/2

Loss conedepletion

Where things get interestingWhere things get interesting

BH separation

Num

ber

0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5

Stallregion?

Hard binary stage: longer than a Hubble time?

Efficient loss-cone repopulation

DANGER!NO astrophysical gravitational wave

background!

Aiming for resultsAiming for results

VIPS resolution limit

LBA resolution limit Sources in a GW regime that will coalesce int = 1/H0 (H0 = 72 km/s/Mpc)

Preliminary CountsPreliminary Counts

CLASS Imaging and spectral indices of ~10000 flat-

spectrum sources 149 sources with multiple flat-spectrum

components identified 22 identified as gravitational lenses

CLASS Imaging and spectral indices of ~10000 flat-

spectrum sources 149 sources with multiple flat-spectrum

components identified 22 identified as gravitational lenses

Preliminary CountsPreliminary CountsAustralia Telescope 20GHz Survey

Blue: spectral index -0.5 Yellow: spectral index -0.3

Rajan Chettri,Ron Ekers

Sho

rt-l

ong

base

line

Vis

ibili

ty r

atio

Preliminary CountsPreliminary Counts

BH separation

N

0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5

10

3

0

50

7

0

90

1

10

13

0

CLASS

0402+379 NGC6240

At the moment… a little bleak

Pulsar timing: Possible discovery of individual GW-emitting

sources Observationally constrained

parameters/scenarios in GWB models Stochastic GWB power spectrum based on

actual sources or predictions from counts With any detections, can put a lower limit on

the GWB for pulsar timing. Direct evidence for close binary black holes

and black hole coalescence

Pulsar timing: Possible discovery of individual GW-emitting

sources Observationally constrained

parameters/scenarios in GWB models Stochastic GWB power spectrum based on

actual sources or predictions from counts With any detections, can put a lower limit on

the GWB for pulsar timing. Direct evidence for close binary black holes

and black hole coalescence

Science aimsScience aims

Merger dynamics & MBH Evolution: Observational check of hierarchical galaxy

formation models Local binary population count Discovering new BH systems: ability to study

host galaxies and post-merger dynamics, timescales.

Merger dynamics & MBH Evolution: Observational check of hierarchical galaxy

formation models Local binary population count Discovering new BH systems: ability to study

host galaxies and post-merger dynamics, timescales.

Science aimsScience aims

(END)(END)

Outline of talkOutline of talk 1. The problem & background

Pulsars detect binaries in a unique frequency range Binary populations unknown GWB models are very unconstrained Galaxy evolution models are very unconstrained

2. How we’re approaching CUT TO THE CHASE: Direct observations of BHs are possible! And will give science. Show N vs a plots, or some a/adot vs

a plots. 3. What will result

No detections: various interpretations; BHBs do not exist, or only exist only for very short periods of time.

An OBSERVED lower limit for a GWB (statistical or actual)

1. The problem & background Pulsars detect binaries in a unique frequency range Binary populations unknown GWB models are very unconstrained Galaxy evolution models are very unconstrained

2. How we’re approaching CUT TO THE CHASE: Direct observations of BHs are possible! And will give science. Show N vs a plots, or some a/adot vs

a plots. 3. What will result

No detections: various interpretations; BHBs do not exist, or only exist only for very short periods of time.

An OBSERVED lower limit for a GWB (statistical or actual)