The Pan-STARRS1 z 5.6 Quasar Survey. III. The z ≈ 6 Quasar Luminosity Function

Media type: E-Article

Title: The Pan-STARRS1 z 5.6 Quasar Survey. III. The z ≈ 6 Quasar Luminosity Function

Contributor: Schindler, Jan-Torge; Bañados, Eduardo; Connor, Thomas; Decarli, Roberto; Fan, Xiaohui; Farina, Emanuele Paolo; Mazzucchelli, Chiara; Nanni, Riccardo; Rix, Hans-Walter; Stern, Daniel; Venemans, Bram P.; Walter, Fabian

Published: American Astronomical Society, 2023

Language: Without Specification

DOI: 10.3847/1538-4357/aca7ca

ISSN: 0004-637X; 1538-4357

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Description: Abstract We present the z ≈ 6 type-1 quasar luminosity function (QLF), based on the Pan-STARRS1 (PS1) quasar survey. The PS1 sample includes 125 quasars at z ≈ 5.7–6.2, with −28 ≲ M 1450 ≲ −25. With the addition of 48 fainter quasars from the SHELLQs survey, we evaluate the z ≈ 6 QLF over −28 ≲ M 1450 ≲ −22. Adopting a double power law with an exponential evolution of the quasar density (Φ(z) ∝ 10 k(z−6); k = −0.7), we use a maximum likelihood method to model our data. We find a break magnitude of M * = − 26.38 − 0.60 + 0.79 mag , a faint-end slope of α = − 1.70 − 0.19 + 0.29 , and a steep bright-end slope of β = − 3.84 − 1.21 + 0.63 . Based on our new QLF model, we determine the quasar comoving spatial density at z ≈ 6 to be n ( M 1450 < − 26 ) = 1.16 − 0.12 + 0.13 cGpc − 3 . In comparison with the literature, we find the quasar density to evolve with a constant value of k ≈ −0.7, from z ≈ 7 to z ≈ 4. Additionally, we derive an ionizing emissivity of ϵ 912 ( z = 6 ) = 7.23 − 1.02 + 1.65 × 10 22 erg s − 1 Hz − 1 cMpc − 3 , based on the QLF measurement. Given standard assumptions, and the recent measurement of the mean free path by Becker et al. at z ≈ 6, we calculate an H i photoionizing rate of ΓH I(z = 6) ≈ 6 × 10−16 s−1, strongly disfavoring a dominant role of quasars in hydrogen reionization.

Access State: Open Access

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