Evolution of the AGN UV luminosity function from redshift 7.5
By Girish Kulkarni, G. Worseck, J. Hennawi. Monthly notices of the Royal Astronomical Society, 2018
153 citations recorded by the source corpus.
Determinations of the ultraviolet (UV) luminosity function of active galactic nuclei (AGN) at high redshifts are important for constraining the AGN contribution to reionization and understanding the growth of supermassive black holes. Recent inferences of the luminosity function suffer from inconsistencies arising from inhomogeneous selection and analysis of data. We address this problem by constructing a sample of more than 80 000 colour-selected AGN from redshift $z$ = 0 to 7.5 using multiple data sets homogenized to identical cosmologies, intrinsic AGN spectra, and magnitude systems. Using this sample, we derive the AGN UV luminosity function from redshift $z$ = 0 to 7.5. The luminosity function has a double power-law form at all redshifts. The break magnitude M* shows a steep brightening from M* ∼ −24 at $z$ = 0.7 to M* ∼ −29 at $z$ = 6. The faint-end slope β significantly steepens from −1.9 at $z$ < 2.2 to −2.4 at $z$ ≃ 6. In spite of this steepening, the contribution of AGN to the hydrogen photoionization rate at $z$ ∼ 6 is subdominant (<3 per cent), although it can be non-negligible (∼10 per cent) if these luminosity functions hold down to M1450 = −18. Under reasonable assumptions, AGN can reionize He ii by redshift $z$ = 2.9. At low redshifts ($z$ < 0.5), AGN can produce about half of the hydrogen photoionization rate inferred from the statistics of H i absorption lines in the intergalactic medium. Our analysis also reveals important systematic errors in the data, which need to be addressed and incorporated in the AGN selection function in future in order to improve our results. We make various fitting functions, codes, and data publicly available.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/5ae9d90b2bd20a216b9f009ec836a53b42738a0f
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Citations in the corpus
- A Census of Photometrically Selected Little Red Dots at 4 < z < 9 in JWST Blank Fields (2024, result): “As an upper limit on number density of quasars at z ∼ 5, we also compare to the results presented in Kulkarni et al. (2019), which combine both UV-bright quasars ( M UV < − 24) and UV-faint X-ray detected AGN (Gi-allongo et al. 2019) in their UVLF.”
- The Rise of Faint, Red Active Galactic Nuclei at z > 4: A Sample of Little Red Dots in the JWST Extragalactic Legacy Fields (2025, unknown): “We fi nd that LRDs are ∼ 4 and ∼ 10 times more numerous at M UV = − 19 than X-ray AGN at z ∼ 5 ( S. Parsa et al. 2018 ) and UV-selected AGN at z ∼ 7 ( G. Kulkarni et al. 2019 ) , respectively.”
- Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, methodology): “Concurrently, the very low fesc reported for bright star-forming galaxies out to z∼4 (see Section 1), and the sharply dropping Active Galactic Nucleus (AGNs) luminosity function (Kulkarni et al. 2019) further shifted the spotlight onto faint star-forming galaxies.”