The Extremely Luminous Quasar Survey in the Sloan Digital Sky Survey Footprint. III. The South Galactic Cap Sample and the Quasar Luminosity Function at Cosmic Noon

Abstract

We have designed the Extremely Luminous Quasar Survey (ELQS) to provide a highly complete census of unobscured UV-bright quasars during the cosmic noon, z = 2.8 − 5.0. Here we report the discovery of 70 new quasars in the ELQS South Galactic Cap (ELQS-S) quasar sample, doubling the number of known extremely luminous quasars in 4, 237.3 deg 2 of the SDSS footprint. These observations conclude the ELQS and we present the properties of the full ELQS quasar catalog, containing 407 quasars over 11, 838.5 deg 2 . Our novel ELQS quasar selection strategy resulted in unprecedented completeness at the bright end and allowed us to discover 109 new quasars in total. This marks an increase of ∼ 36% (109/298) to the known population at these redshifts and magnitudes, while we further are able to retain a selection efficiency of ∼ 80%. On the basis of 166 quasars from the full ELQS quasar catalog, who adhere to the uniform criteria of the 2MASS point source catalog, we measure the bright-end quasar luminosity function (QLF) and extend it one magnitude brighter than previous studies. Assuming a single power law with exponential density evolution for the functional form of the QLF, we retrieve the best fit parameters from a maximum likelihood analysis. We find a steep bright-end slope of β ≈ −4.1 and we can constrain the bright-end slope to β ≤ −3.4 with 99% confidence. The density is well modeled by the exponential redshift evolution, resulting in a moderate decrease with redshift (γ ≈ −0.4).

Evolution of the AGN UV luminosity function from redshift 7.5

“…At high redshifts, our parameter values are closest to those reported by Yang et al (2016) at z = 4.7-5.4 and by Schindler et al (2019) at z = 2.8-5. Figure B1 suggests that it is incorrect to fix QLF parameters while fitting QLF models and one should only fit models if data actually span the magnitude range.…”

“…Note that the photoionization rate calculation assumes an H I column density distribution given by Haardt & Madau (2012) and extrapolates this to high redshifts. log 10 φ * /mag −1 cMpc −3 Croom et al 2009Schulze et al 2009Glikman et al 2011Masters et al 2012McGreer et al 2013Ross et al 2013Giallongo et al 2015Jiang et al 2016Yang et al 2016Onoue et al 2017Akiyama et al 2018McGreer et al 2018Matsuoka et al 2018Schindler et al 2019Kulkarni et al 2019 Table D1. Comoving emissivities at 912Å and 1450Å derived from our double power law luminosity function models in redshift bins (Table 2) for two magnitude limits.…”

Ionizing radiation from AGNs at z>3.3 with the Subaru Hyper Suprime-Cam Survey and the CFHT Large Area U-band Deep Survey (CLAUDS)

“…Because these UVLFs predict higher number density of faint AGNs, the emissivity values using these UVLFs are 2 to 5 times higher than the values with the UVLF by Akiyama et al (2018). Also, because the redshift interval of the results by Giallongo et al (2015) we use in this study is z = 4 to 4.5, if we adopt a number density evolution φ(z) ∝ 10 −0.38z suggested by Schindler et al (2019), the number density at z = 3.4 will be a factor of ∼2 higher. In such case, the LyC emissivity by AGNs could be as high as ∼40-50% of the nominal value at z = 3.2 by Becker & Bolton (2013).…”

The Mass Function of Supermassive Black Holes in the Direct-collapse Scenario

“…This is in contrast to the usual practice of fitting the observed QLF with a double power law (e.g., Hopkins 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 L/L al. 2007;Masters et al 2012;Schindler et al 2019) that requires three parameters: the two power-law indices and a joining point.…”