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arXiv · 2110.13736

The space density of ultra-luminous QSOs at the end of reionization epoch by the QUBRICS Survey and the AGN contribution to the hydrogen ionizing background

A. Grazian·E. Giallongo·K. Boutsia·G. Calderone·S. Cristiani·G. Cupani·F. Fontanot·F. Guarneri·Y. Ozdalkiran
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Abstract

Motivated by evidences favoring a rapid and late hydrogen reionization process completing at z~5.2-5.5 and mainly driven by rare and luminous sources, we have reassessed the estimate of the space density of ultra-luminous QSOs at z~5 in the framework of the QUBRICS survey. A ~90% complete sample of 14 spectroscopically confirmed QSOs at M1450<-28.3 and 4.5 3. Adopting our z~4 QSO luminosity function and applying a mild density evolution in redshift, a photo-ionization rate of GammaHI=0.46+0.17-0.09x10^-12 s^-1 has been obtained at z=4.75, assuming an escape fraction of ~70% and a steep faint-end slope of the AGN luminosity function. The derived photo-ionization rate is ~50-100% of the ionizing background measured at the end of the reionization epoch, suggesting that AGNs could play an important role in the cosmological reionization process.

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A. Grazian, E. Giallongo, K. Boutsia, G. Calderone, S. Cristiani, G. Cupani, F. Fontanot, F. Guarneri, Y. Ozdalkiran. 2021-10-26. The space density of ultra-luminous QSOs at the end of reionization epoch by the QUBRICS Survey and the AGN contribution to the hydrogen ionizing background. https://doi.org/10.3847/1538-4357%2Fac33a4

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