New bounds on axion-like particles in the ultraviolet from legacy data

Abstract We use legacy data from the Hubble Space Telescope (HST) and the International Ultraviolet Explorer (IUE) to search for a spectral line from the spontaneous decay of axion-like particle (ALP) dark matter. The HST data consist of blank sky observations taken with the Faint Object Spectrograph in the 165–240 nm wavelength range, while the IUE data consist of observations of the Virgo Cluster obtained with the long- and short-wavelength spectrographs, covering 195–325 nm and 123–200 nm, respectively. We set a 95% C.L. upper limit on the ALP-photon coupling g aγ ≲ 10 -11 GeV -1 across the whole probed ALP mass range. Notably, we rule out values of g aγ above 2.3 × 10 -12 GeV -1 for ALP masses between 12.4 and 14.5 eV, improving upon previous limits by a factor of seven.