Pulsar Key Science with the SKA

Transcription

1 Pulsar Key Science with the SKA Strong-field tests of gravity using Pulsars and Black Holes Michael Kramer Krabi, April 2007

2 Pulsar Key Science with the SKA Strong-field tests of gravity using Pulsars and Black Holes Michael Kramer Krabi, April 2007

3 Pulsar Key Science with the SKA Strong-field tests of gravity using Pulsars and Black Holes Michael Kramer Krabi, April 2007

4 The question

5 Some clues to the answer Experiments made in Solar System provide precise tests - Lunar Laser Ranging - Space-craft communication, e.g. Cassini - Rader reflections at planets - Gyro-experiments, e.g. Gravity-Probe B - etc. which GR all passed with flying colours!

6 Some further, unexpected clues the discovery of Dark Energy from cosmology experiments is consistent with general relativity but only when assuming a cosmological constant the implied value for the vacuum energy density is vastly incompatible with particle physics (by % Dark Energy normal matter Dark matter orders of magnitude), i.e. physics is incompatible by a factor of ~ /04/ SKA Pulsar Workshop!! 5% 25%

7 Do we need new physics? General relativity? Relativistic Gravity (large scale) Quantum Gravity Quantum Mechanics (small scale) Standard particle physics model? Can we find an experiment that breaks either theory? e.g.: Will the LHC find the Higgs? Will we make an observation where GR breaks down?

8 Where can we expect to see deviations from GR? Experiments made in Solar System provide precise tests but only in weak gravitational field! In strong gravitational fields, physics may be different! e.g. additional scalar field may appear only in strong fields: Scalar Charge (for β 0 =-6) Damour & Esposito-Farese (1996) Scalarisation

9 Where can we expect to see deviations from GR? Experiments made in Solar System provide precise tests but only in weak gravitational field! In strong gravitational fields, physics may be different! Compute energy in gravitational field: Neutron stars & Black Holes: ε ε NS BH Solar system: ε Sun Earth Moon Weak field experiments alone are not sufficient! ε ε ε = E gravity 2 mc

10 Was Einstein right? log(gm/rc 2 ) log(gm/ac 2 )

11 Was Einstein right? log(2gm/ac 2 ) log(m[m ])

12 Galactic Census with the SKA The pulsar experiment: Find most/all pulsars in Galaxy Timing of discovered binary and millisecond pulsars to very high precision: Find them! Time them! VLBI them! Benefiting from SKA twice: Unique sensitivity: many pulsars, ~10,000-30,000 Not just a continuation incl. of many what rare has systems! been done before Unique timing - Complete precision and new multiple quality of beams! science possible!

13 Pulsar Science with the SKA Very wide range of applications: Galactic probes: Interstellar medium/magnetic field Magnetic field Star formation history Dynamics Population via distances (ISM, VLBI) Electron distribution Movement in potential Galactic Centre

14 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars: Formation & Population Search nearby galaxies! Turbulent magnetized IGM Giant pulses Reach the local group!

15 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics: Radio emission Resolving magnetospheres Relation to high-energies

16 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics Extreme Dense Matter Physics: Ultra-strong B-fields Equations-of-State Core collapses Variation of G

17 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics Extreme Dense Matter Physics Multi-wavelength studies: Photonic windows

18 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics Extreme Dense Matter Physics Multi-wavelength studies: Photonic windows Non-photonic windows

19 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics Extreme Dense Matter Physics Multi-wavelength studies Exotic systems: planets millisecond pulsars relativistic binaries double pulsars PSR-BH systems 3.Holy Grail: PSR-BH Double Pulsars Planets

20 Pulsar Science with the SKA Very wide range of applications: Galactic probes Extragalactic pulsars Relativistic plasma physics Extreme Dense Matter Physics Multi-wavelength studies Exotic systems Gravitational physics: - Ultra-strong gravity - BH properties - Study of Gravitational Wave Background

21 Criteria for selection of KSP Selection followed the submission of proposals: A KSP must address a yet unanswered fundamental question in physics or astrophysics can only be done in the radio with the SKA or the SKA plays at least a decisive role in answering the question must excite the funding agencies and general public Was Einstein right? Featuring What are the Black Hole properties? Do naked singularities exist? Do Black Holes have hairs? What is the nature of the cosmological gravitational wave background?

22 SKA Key Science Projects Key science selected by international community: Strong-field tests of gravity using pulsars & black holes Galaxy evolution, cosmology and dark energy Probing the dark ages The origin and evolution of cosmic magnetism The cradle of life Exploration of the unknown Each KSP has one/two shepherds Detailed science case published in New Astronomy Reviews, 2004 eds Carilli & Rawlings, Vol 48, 11-12

23 Current SKA structure SKA was born global ; >50 institutes in 18 countries actively involved International Science Advisory Committee International Collaboration Working Group International SKA Steering Committee Executive Committee International SKA Project Office International Engineering Advisory Committee International Site Selection Advisory Committee Engineering Working Group Site Evaluation Working Group Science Working Group Simulations Working Group Outreach Committee Operations Working Group

24 SKA Timeline Initial concept First SKA Working Group ISSC MoAs Science Case published Site ranking Intergovernmental discussions Site Selection 1% SKA Science 10% SKA Science SKA Complete Feasibility study Concept exposition Optimise Reference Design Define SKA System Phase 1 Build 10% SKA Full array Build 100% SKA Construct 1% SKA pathfinders Pathfinders are world-class facilities in their own right! It will be a lot of fun!!

25 Gravity Key Science Project Discovering PSR-BH binaries Discovering PSR around GC-BH Measuring BH properties: - No-hair theorem - Cosmic Censorship conjecture 26/04/2007 Detect AND STUDY GW signals Stochastic background from - MBH-MBH mergers - Cosmic strings etc. Single source detection GW spectra SKA Pulsar Workshop

26 Gravity Key Science Project 1. Survey the Galaxy 2. Survey the Galactic Centre 3. Time the discovered pulsars to identify the interesting pulsars 4. Perform long-term high-precision timing on selected pulsars 5. Use VLBI observations to measure proper motion and parallax 26/04/2007 SKA Pulsar Workshop

27 Some important questions How to do the survey? What is the optimal configuration? How to do the beam forming? How to do the processing? How can we process quickly to monitor whole sky for transients? How do we time 20,000 or more pulsars? The problems: Data rates, Computing, Efficiency Some progress since Sydney, August 2005 reported here but more to be done!!