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Pulsar Timing and Galaxy Evolution Common Ground in the GWB Sarah Burke Swinburne University/ATNF ATNF GW Mtg December 12, 2008 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: mBH > ~106 MSun GW 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) 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 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? Characteristic Strain Stochastic GWB Sources Gravitational wave frequency 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. 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a FF (LZW) decompressor eeded to see this picture. 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) log amplitude 0402+379 Rodriguez et al. 2006 Double nucleus log amplitude log frequency Direct Detection: Spatially Resolved Systems log frequency Parameter space 2-point correlations Number CLASS Galaxy merger rates VLBI Pulsar timing sensitivity AT20G Chance radio, xray double detections 0 1 10 100 1000 1e4 1e5 1e6 1e7 1e8 ---> Integrated over redshift bin and BH mass range Linear separation between most massive galactic BHs (pc) Parameter space Number Galaxy groups, large scale clustering, chance projeted separations Bound binary BH systems 0 1 10 100 1000 1e4 1e5 1e6 1e7 1e8 ---> Integrated over redshift bin and BH mass range Linear separation between most massive galactic BHs (pc) Where things get interesting Number 3-body interactions with stellar background GW emission; final inspiral Binary hardening Jaffe and Backer (2003): N a13/2 0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5 BH separation Where things get interesting Number Hard binary stage: longer than a Hubble time? DANGER! NO astrophysical Efficient loss-cone gravitational wave repopulation background! Stall region? 0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5 BH separation Aiming for results LBA resolution limit VIPS resolution limit Sources in a GW regime that will coalesce in t = 1/H0 (H0 = 72 km/s/Mpc) Preliminary Counts CLASS Imaging and spectral indices of ~10000 flatspectrum sources 149 sources with multiple flat-spectrum components identified 22 identified as gravitational lenses Preliminary Counts Short-long baseline Visibility ratio Australia Telescope 20GHz Survey Blue: spectral index -0.5 Yellow: spectral index -0.3 Rajan Chettri, Ron Ekers Preliminary Counts At the moment… a little bleak 10 30 50 70 N 90 110 130 CLASS 0402+379 NGC6240 0 1e-3 1e-2 0.1 1 10 100 1000 1e4 1e5 BH separation Science aims 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. (END) Outline of talk 1. The problem & background 2. How we’re approaching Pulsars detect binaries in a unique frequency range Binary populations unknown GWB models are very unconstrained Galaxy evolution models are very unconstrained 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)