Lyman continuum leaking AGN in the SSA22 field

作者：Micheva Genoveva; Iwata Ikuru; Inoue Akio K

来源：Monthly Notices of the Royal Astronomical Society, 2017, 465(1): 302-315.

DOI：10.1093/mnras/stw1329

• galaxies: evolution
• galaxies: high-redshift
• intergalactic medium
• cosmology: observations
• diffuse radiation

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 f(esc) = 1. Comparing to recent Ly alpha forest measurements, AGNs at redshift z similar to 3 make up at most similar to 12 per cent and as little as similar to 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.

• 出版日期2017-2-11
• 单位中国科学院国家天文台