Observations of 3C 390.3 with the International Ultraviolet Explorer.

Abstract

Observations of the radio galaxy 3C 390.3 made with IUE are presented; these allow separate determinations of the Lyman/Balmer ratios in both the narrow and broad emission-line regions. The broad-line L-alpha/H-alpha ratio confirms the anomalous results found previously in quasars; in this case a ratio is found about 15 times smaller than that predicted by simple recombination models. By contrast, the L-alpha/H-alpha ratio found for the lower-density narrow-line region is nearly normal. It is argued that the broad-line spectrum can be interpreted in terms of collisional processes at high densities (electron densities of 10 billion to 25 billion per cu cm).