Pulsar Timing and Galaxy Evolution Sarah Burke Swinburne University/ATNF ATNF GW Mtg December 12, 2008 Sarah Burke Swinburne University/ATNF ATNF GW Mtg December 12, 2008 Common Ground in the GWB Supervisors: Matthew Bailes, David Barnes, Simon Johnston, Dick Manchester In collaboration with: Dick Manchester, Ron Ekers, Chris Phillips

CLAIM Pulsar timing should detect GW emission from binary supermassive black hole (SMBH) systems at sub-pc separations Supermassive: m BH > ~10 6 M Sun

GW detection from PTing GWB A background of emission from hard binaries Supermassive systems with BH mass ratio >0.3 P orb = 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 P orb = s Contributing population anywhere from z = 0 to high redshift (z > 6) Single source Nearby (z<1) P orb = 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 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 Sources Gravitational wave frequency Characteristic Strain

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.

CLAIM Identification 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 Methods Et cetera

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 Rodriguez et al log frequency log amplitude log frequency log amplitude Double nucleus

VLBI Parameter space Number e4 1e5 1e6 1e7 1e8 ---> AT20G CLASS 2-point correlations Galaxy merger rates Chance radio, xray double detections Pulsar timing sensitivity Integrated over redshift bin and BH mass range Linear separation between most massive galactic BHs (pc)

Parameter space Linear separation between most massive galactic BHs (pc) Number e4 1e5 1e6 1e7 1e8 ---> Integrated over redshift bin and BH mass range Bound, merging galaxies/halos Massive objects falling to centre; dynamical friction Bound binary BH systems Galaxy groups, large scale clustering, chance projeted separations

Where things get interesting BH separation Number 0 1e-3 1e e4 1e5 Dynamical friction 3-body interactions with stellar background Binary hardening GW emission; final inspiral Jaffe and Backer (2003): N  a 13/2 Loss cone depletion

Where things get interesting BH separation Number 0 1e-3 1e e4 1e5 Stall region? Hard binary stage: longer than a Hubble time? Efficient loss-cone repopulation DANGER! NO astrophysical gravitational wave background!

Aiming for results VIPS resolution limit LBA resolution limit Sources in a GW regime that will coalesce in t = 1/H 0 (H 0 = 72 km/s/Mpc)

Preliminary 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 Counts Australia Telescope 20GHz Survey Blue: spectral index -0.5 Yellow: spectral index -0.3 Rajan Chettri, Ron Ekers Short-long baseline Visibility ratio

Preliminary Counts BH separation N 0 1e-3 1e e4 1e CLASS 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 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 aims

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Outline 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)