Axions and X-ray astronomy

Transcription

1 Axions and X-ray astronomy Francesca Day University of Cambridge Alsatian Workshop on X-ray Polarimetry November : M Berg, J Conlon, FD, N Jennings, S Krippendorf, A Powell & M Rummel : J Conlon, FD, N Jennings, S Krippendorf & M Rummel : J Conlon, FD, N Jennings, S Krippendorf & F Muia Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

2 Reproduced from Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

3 Outline 1 Axions 2 Axion searches in X-rays 3 Conclusions Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

4 Axions Axions Axions are ultra-light particles that exist in many extensions of the Standard Model Explain null measurements of the neutron electric dipole moment String theory compactificiations typically give rise to many axions at a range of masses Axions can act as both dark matter and dark energy Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

5 Axions Axions L = 1 2 µa µ a 1 2 m2 aa 2 + a M E B L a E B leads to axion-photon interconversion in the M presence of a background magnetic field. Model axion-photon conversion with classical equation of motion from L. Assume that the axion wavelength is much shorter than the scale over which its environment changes, allowing us to linearise the equations of motion. Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

6 Axions Axion-photon conversion ω + γ 0 γax 0 γ γay γax γay a i z γ x γ y a = 0 γ = ω2 pl 2ω Plasma frequency: ω pl = ( ) 1 4πα ne 2 m e a = m2 a ω. Here we take m a = 0. This is valid for m a ev. Mixing: γai = B i 2M P a γ (L) = 1, 0, 0 f (L) 2 + 0, 1, 0 f (L) 2 Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

7 Axions Axion-photon conversion P a γ B2 M 2 for B2 M 2 1 P a γ increases with the field coherence length and the total extent of the field. High electron densities increase the effective photon mass, suppressing conversion. Astrophysical environments lead to the highest conversion probabilities. Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

8 Axions Limits Axion Coupling G Aγγ (GeV -1 ) SN 1987A LSW (OSQAR) Helioscopes (CAST) HESS Haloscopes (ADMX) Horizontal Branch Stars KSVZ DFSZ Axion Mass m A (ev) VMB (PVLAS) Telescopes Reproduced from the Particle Data Group Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

9 Axion searches in X-rays Spectral Modulations We search for axions by studying the X-ray spectra of point sources in or behind galaxy clusters. See also J P Conlon et al, ; D Wouters and P Brun, ; P Brax et al, ; The Fermi-LAT Collaboration, ; M C D Marsh et al, Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

10 Axion searches in X-rays Galaxy clusters Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

11 Axion searches in X-rays Photon survival probability Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

12 Axion searches in X-rays Photon-Axion Conversion Photon to axion conversion can lead to modulations in an initially pure photon spectrum, given by the photon survival probability P γ γ (E). At X-ray energies in galaxy clusters, P γ γ (E) is pseudo-sinusoidal in 1 E. Axion induced oscillations in P γ γ (E) would be imprinted on the observed spectrum. We seek to constrain M by searching for such oscillations. Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

13 Axion searches in X-rays Analysis We analyse 8 likely looking point sources: The AGN NGC1275 at the centre of Perseus The quasars B and SDSS J shining through Coma The AGN NGC3862 in A1367 The AGN IC4374 at the centre of A3581 The bright Sy1 galaxy 2E3140 within A1795 The quasar CXOU J behind A1795 The central AGN UGC9799 of the cluster A2052 Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

14 Axion searches in X-rays Example: NGC3862 in A1367 Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

15 Axion searches in X-rays Bounds The leading bounds are from NGC1275 in Perseus, 2E3140 in A1795 and M87 in Virgo (D Marsh et al, ): M GeV. Axion Coupling G Aγγ (GeV -1 ) LSW (OSQAR) Helioscopes (CAST) NGC Perseus Horizontal Branch Stars SN 1987A Fermi-LAT HESS Haloscopes (ADMX) KSVZ DFSZ VMB (PVLAS) Telescopes Axion Mass m A (ev) Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

16 Axion searches in X-rays Projected bounds with Athena Axion Coupling G Aγγ (GeV -1 ) LSW (OSQAR) Helioscopes (CAST) NGC Chandra NGC Athena Horizontal Branch Stars SN 1987A Fermi-LAT HESS Haloscopes (ADMX) KSVZ DFSZ VMB (PVLAS) Telescopes Axion Mass m A (ev) Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17

17 Conclusions Conclusions Axions are a well motivated dark matter candidate. Axions and photons interconvert in the presence of a background magnetic field. Astrophysical magnetic fields offer powerful opportunities to search for axions. Points sources passing through galaxy clusters have the potential to place world leading bounds on the axion photon interaction. Francesca Day (University of Cambridge) Axions and X-ray astronomy Strasbourg / 17