Telescope search for decaying relic axions
A search for optical line emission from the two-photon decay of relic axions was conducted in the galaxy clusters Abell 2667 and 2390, using spectra from the VIMOS (Visible MultiObject Spectrograph) integral field unit at the Very Large Telescope. New upper limits to the two-photon coupling of the axion are derived, and are at least a factor of 3 more stringent than previous upper limits in this mass window. The improvement follows from a larger collecting area, integration time, and spatial resolution, as well as from improvements in signal to noise and sky subtraction made possible by strong-lensing mass models of these clusters. The new limits either require that the two-photon coupling of the axion be extremely weak or that the axion mass window between 4.5 eV and 7.7 eV be closed. Implications for sterile-neutrino dark matter are discussed briefly also.
Additional Information© 2007 The American Physical Society (Received 14 November 2006; revised 27 March 2007; published 25 May 2007) The authors thank Ted Ressell and Matthew Bershady for helpful discussions. D.G. was supported by the Gordon and Betty Moore Foundation. G.C. acknowledges support from the European Community via the Marie Curie European Re-Integration Grant No. 029159. J.-P.K. acknowledges support from the CNRS. M.K. was supported in part by D.O.E. DE-FG03-92-ER40701, NASA NNG05GF69G, and the Gordon and Betty Moore Foundation. A.W.B. thanks the Alfred P. Sloan Foundation and Research Corporation for support.
Published - GRIprd07.pdf