Do the broad emission line clouds see the same continuum that we see?

Kirk Korista, Gary Ferland, Jack Baldwin

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


Recent observations of quasars, Mrk 335 and the HST quasar composite spectrum, have indicated that many quasars have remarkably soft ionizing continua (fv∝v-2, 13.6-100 eV). We point out that the number of photons with hv > 54.4 eV is insufficient to create the observed strengths of the He II emission lines. While the numbers of photons which energize C IV λ1549 and O VI λ1034 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 being the observed soft X-ray excess.

Original languageEnglish
Pages (from-to)555-559
Number of pages5
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1997


  • Line: formation
  • Quasars: emission lines
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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