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http://hdl.handle.net/20.500.12386/31891
Titolo: | The Luminosity Function of Bright QSOs at z ∼ 4 and Implications for the Cosmic Ionizing Background | Autori: | Boutsia, Konstantina GRAZIAN, Andrea FONTANOT, Fabio GIALLONGO, Emanuele MENCI, Nicola CALDERONE, GIORGIO CRISTIANI, Stefano D'ODORICO, Valentina CUPANI, Guido GUARNERI, FRANCESCO Omizzolo, Alessandro |
Data pubblicazione: | 2021 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 912 | Fascicolo: | 2 | Da pagina:: | 111 | Abstract: | Based on results by recent surveys, the number of bright quasars at redshifts z > 3 is being constantly revised upward. The current consensus is that at bright magnitudes (M<SUB>1450</SUB> ≤ -27) the number densities of such sources could have been underestimated by a factor of 30%-40%. In the framework of the QUBRICS survey, we identified 58 bright QSOs at 3.6 ≤ z ≤ 4.2, with magnitudes i<SUB>psf</SUB> ≤ 18, in an area of 12400 deg<SUP>2</SUP>. The uniqueness of our survey is underlined by the fact that it allows us, for the first time, to extend the sampled absolute magnitude range up to M<SUB>1450</SUB> = -29.5. We derived a bright-end slope of β = -4.025 and a space density at <M<SUB>1450</SUB>> = -28.75 of 2.61 × 10<SUP>-10</SUP> Mpc<SUP>-3</SUP> comoving, after taking into account the estimated incompleteness of our observations. Taking into account the results of fainter surveys, active galactic nuclei (AGNs) brighter than M<SUB>1450</SUB> = -23 could produce at least half of the ionizing emissivity at z ∼ 4. Considering a mean escape fraction of 0.7 for the QSO and AGN population, combined with a mean free path of 41.3 proper Mpc at z = 3.9, we derive a photoionization rate of ${\rm{Log}}({\rm{\Gamma }}\left[{{\rm{s}}}^{-1}\right])=-{12.17}_{-0.07}^{+0.13}$ , produced by AGNs at M<SUB>1450</SUB> < -18, that is, ∼100% of the measured ionizing background at z ∼ 4. | URI: | http://hdl.handle.net/20.500.12386/31891 | URL: | https://iopscience.iop.org/article/10.3847/1538-4357/abedb5 https://api.elsevier.com/content/abstract/scopus_id/85106206565 |
ISSN: | 0004-637X | DOI: | 10.3847/1538-4357/abedb5 | Bibcode ADS: | 2021ApJ...912..111B | Fulltext: | open |
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