ACTIVE GALACTIC NUCLEI SELECTED FROM GALEX SPECTROSCOPY: THE IONIZING SOURCE SPECTRUM AT z ∼ 1

We use a complete sample of Ly alpha-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700 -900 angstrom) at z similar to 1. Our sample consists of 139 sources selected in the redshift range z = 0.65 -1.25 in the near-ultraviolet (NUV; 2371 angstrom central wavelength) channel. The area covered is 8.2 deg(2) to a NUV magnitude of 20.5 (AB) and 0.92 deg(2) at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 angstrom central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z similar to 1 in a fully self-consistent way.