The Strength of Hβ in Extragalactic Objects with Broad Emission Lines

We point out that the equivalent width of the Hj3 emission line in extragalactic objects with broad Balmer emission lines is always less than the value expected from recombination theory by about the same large factor. This can be understood if the following conditions are satisfied: (a) the gas in all these objects is ionized by non-thermal radiation, (b) in all the objects the non-thermal radiation has roughly the same spectral index, and (c) this value of the spectral index persists below the Lyman limit