Lyman continuum leaking AGN in the SSA22 field

Genoveva Micheva*, Ikuru Iwata, Akio K. Inoue

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin nature or are foreground contaminants. The remaining two LyC candidates are type I AGN.We argue that the average LyC escape fraction of high-redshift, low-luminosityAGNis not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of 2 lower than values obtained assuming fesc = 1. Comparing to recent Ly α forest measurements, AGNs at redshift z ~ 3 make up at most ~12 per cent and as little as ~5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

Original languageEnglish
Pages (from-to)302-315
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 2017 Feb 11
Externally publishedYes


  • Cosmology: observations
  • Diffuse radiation
  • Galaxies: evolution
  • Galaxies: high-redshift
  • Intergalactic medium

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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