Cosmic UV background spectra with New Horizons

These observations were taken at about 57AU from the Sun, outside much of the foreground emission affecting previous missions, and allowed a new determination of the spectrum of the CUVB between 912-1100{AA} and 1400-1800{AA}. We found a linear correlation between the CUVB and the Planck E(B-V) with offsets at zero-reddening of 221+/-11 photon units at 1000{AA} and 264+/-24 photon units at 1500{AA} (4.4+/-0.2nW/m2/sr at 1000{AA} and 5.3+/-0.5nW/m/sr at 1500{AA}).

The former is the first firm detection of the offset in the range 912-1100{AA} while the latter result confirms previous results from the Galaxy Evolution Explorer, showing that there is little emission from the solar system from 1400 to 1800{AA}. About half of the offset may be explained by known sources (the integrated light of unresolved galaxies, unresolved stars, emission from ionized gas, and two-photon emission from warm hydrogen in the halo) with the source of the remaining emission as yet unidentified.