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Radio Astronomy Search for Axion Dark Matter: SKA Insights

Explore the methodologies and results of the search for cold dark matter axions using radio astronomy, presenting novel spectral features and the significance of astrophysical magnetic fields. Dive into the challenges, approaches, and potential outcomes in this cutting-edge study.

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Radio Astronomy Search for Axion Dark Matter: SKA Insights

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  1. Searching for Cold Dark Matter Axionswith the SKA Katharine Kelley 3 June 2019 Supervisor Prof. Peter Quinn

  2. Agenda • Introduction • Where were we two years ago – what’s changed? • The challenge with astrophysical observation • Non-resonant conversion • Astrophysical magnetic fields • Approach • Results: Unique Spectral Features • Results: Central Molecular Zone • Pulsars: Key Considerations and Results • Summary A Radio Astronomy Search for Axion Dark Matter

  3. Introduction A Radio Astronomy Search for Axion Dark Matter

  4. Introduction • Compton Frequency • 10-6 – 10-3eV0.2 – 200GHz A Radio Astronomy Search for Axion Dark Matter

  5. Axion-two photon coupling • Non-resonant conversion of a cold axion: • momentum required from the virtual photon to satisfy E=pc- direction of propagation therefore perpendicular to the field • Dependency on the spatial profile of the field • Non-static fields may contribute energy to the interaction • Changes in environment may impact rate • Resonant conversion: • Axion and real photon have the same properties • Field transverse to propagation of axion contributes to conversion • Astrophysically the real photon requires an ‘effective mass’ to balance energy - momentum • Direction of propagation of real photon the same as the axion A Radio Astronomy Search for Axion Dark Matter

  6. New Radio Telescopes 0.7 – 1.8GHz 0.4 – 2.5 GHz 2.5 – 13.8 GHz 0.4 – 13.8 GHz Axion Mass: ~ 1.7 – 57 μ eV A Radio Astronomy Search for Axion Dark Matter

  7. New Radio Telescopes SKA1-low: 130,000 dipoles 70 – 350 MHz MWA 70 – 300 MHz A Radio Astronomy Search for Axion Dark Matter

  8. Why the SKA? A Radio Astronomy Search for Axion Dark Matter

  9. 20172019 A Radio Astronomy Search for Axion Dark Matter

  10. Radio Telescopes • Observations of the Central Molecular Zone • Turbulent magnetic fields • Non-resonant axion conversion • Magnetic energy over millimetre to metre length scales A Radio Astronomy Search for Axion Dark Matter

  11. Photon Production Rate Static Field Non-Static Field Very Challenging Static Field 1 – 1,000 m-1 Presentation Title (Edit in File > 'Page Setup’ > ‘Header/footer’)

  12. Approach A Radio Astronomy Search for Axion Dark Matter

  13. Astrophysical Magnetic Fields Central Molecular Zone: 130 micro G ISM (MW and M31): 50 micro G decaying r-1 Galaxy cluster: Core ~ 4 micro G Pulsars: B < 109 T A Radio Astronomy Search for Axion Dark Matter

  14. Astrophysical Magnetic Fields Galactic Centre: R ~ 1 kpc B ~ 10-3 G ISM: R ~ 10s kpc B ~ 10-6G Galaxy clusters: R ~ 1000s kpc B ~ 10-6 G Pulsars: R ~ 1 km B ~ 109 - 1012G A Radio Astronomy Search for Axion Dark Matter

  15. Dark Matter Density A Radio Astronomy Search for Axion Dark Matter

  16. Results:Unique Spectral Features A Radio Astronomy Search for Axion Dark Matter

  17. Natural Spectral Features • Unique spectral features • Strength proportional to: • - dark matter density • - square of the magnetic field • - volume observed • - integration time • - distance to source • Polarisation given by the B field – perpendicular to synchrotron radiation • Central frequency: • - 0.2 – 200 GHz for conversion in a static field • Maxwellian profile: axion velocity distribution in the frame of conversion • The frame of the B field sets the frame of conversion Frames of Reference A Radio Astronomy Search for Axion Dark Matter

  18. Unique Spectral Profiles Central Molecular Zone Galaxy Cluster Andromeda Interstellar Medium A Radio Astronomy Search for Axion Dark Matter

  19. Results: Central Molecular Zone A Radio Astronomy Search for Axion Dark Matter

  20. CMZ: Low Density Plasma A Radio Astronomy Search for Axion Dark Matter

  21. Axion Coupling - CMZ A Radio Astronomy Search for Axion Dark Matter

  22. Pulsars: Key considerations and Results A Radio Astronomy Search for Axion Dark Matter

  23. Pulsars • Density: 1015 – 1016 m-3 • Conversion frame is rotating • Non-resonant vs resonant conversion • Solar dark matter density • Vacuum polarisation effect • Non-static components of the field • ~ 1,000 ATNF vs 107 • Same frame as the Earth Presentation Title (Edit in File > 'Page Setup’ > ‘Header/footer’)

  24. Flux and Spectral Profiles Presentation Title (Edit in File > 'Page Setup’ > ‘Header/footer’)

  25. Pulsars Presentation Title (Edit in File > 'Page Setup’ > ‘Header/footer’)

  26. Summary • Non-resonant conversion very challenging due to scale of magnetic field • Best opportunity may be nearby pulsars, modelling shows 107 within 5kpc • Unique spectral profile for each observation could support identification • Very difficult to exclude regions of parameter space due to uncertainty over field structure • Could support identification if a detection is made in the laboratory • Investigation of unidentified spectral lines should continue • Neutron star mergers, binary stars, AGN A Radio Astronomy Search for Axion Dark Matter

  27. Coma Cluster A Radio Astronomy Search for Axion Dark Matter

  28. ISM: Milky Way A Radio Astronomy Search for Axion Dark Matter

  29. ISM: Andromeda A Radio Astronomy Search for Axion Dark Matter

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