Do the Broad Emission Line Clouds See the Same Continuum that We See?

Kirk Korista, Gary Ferland, Jack Baldwin

Published 1997-04-27Version 1

Recent observations of quasars, Mrk 335 and the HST quasar composite spectrum, have indicated that many of them have remarkably soft ionizing continua (fnu ~ nu^-2.0, 13.6 eV -- 100 eV). We point out that the number of E > 54.4 eV photons is insufficient to create the observed strengths of the He II emission lines. While the numbers of photons which energize C IV 1549 and O VI 1034 are sufficient, even the most efficiently emitting clouds for these two lines must each cover at least 20% -- 40% of the source. If the typical quasar ionizing continuum is indeed this soft, then we must conclude that the broad emission line clouds must see a very different (harder) continuum than we see. The other viable possibility is that the UV -- EUV SED is double-peaked, with the second peaking near 54 eV, its Wien tail the observed soft X-ray excess.