Lyman continuum leaking AGN in the SSA22 field

• Published in: Monthly notices of the Royal Astronomical Society Vol. 465; no. 1; p. 302
• Main Authors: Micheva, Genoveva, Iwata, Ikuru, Inoue, Akio K
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 11.02.2017
• Subjects: Active galactic nuclei; Astronomy; Budgeting; Contaminants; Continuums; Flux; Luminosity; Red shift; Spectrum analysis; Unity; Universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw1329

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-luminosity AGN is 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 f sub( esc) = 1. Comparing to recent Ly a 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.