The total rest-frame UV luminosity function from $3 < z < 5$: A simultaneous study of AGN and galaxies from $-28

Abstract

We present measurements of the rest-frame ultraviolet luminosity function (UV LF) at redshifts 𝑧 = 3, 𝑧 = 4 and 𝑧 = 5, using 96894, 38655 and 7571 sources respectively to map the transition between AGN and galaxy-dominated ultraviolet emission shortly after the epoch of reionization. Sources are selected using a comprehensive photometric redshift approach, using 10 deg 2 of deep extragalactic legacy fields covered by both HSC and VISTA. The use of template fitting spanning a wavelength range of 0.3-2.4𝜇m achieves 80-90 per cent completeness, much higher than classical colour-colour cut methodology. The measured LF encompasses −26 < 𝑀 UV < −19.25(−20.5) at 𝑧 = 3(5). This is further extended to −28.5 < 𝑀 UV < −16 using complementary results from other studies, allowing for the simultaneous fitting of the combined AGN and galaxy LF. We find that there are fewer UV luminous galaxies (𝑀 UV < −22) at 𝑧 ∼ 3 than 𝑧 ∼ 4, indicative of an onset of widespread quenching alongside dust obscuration, and that the evolution of the AGN LF is much more rapid than the galaxy LF, with their number density rising by around 2 orders of magnitude from 3 < 𝑧 < 6. We also find that it remains difficult to determine if a double power law (DPL) functional form is preferred over the Schechter function to describe the galaxy UV LF with photometric data alone. Estimating the Hydrogen ionizing photon budget from our UV LFs, we find that AGN can contribute to, but cannot solely maintain, the reionization of the Universe at 𝑧 = 3 − 5. However, the rapidly evolving AGN LF strongly disfavours a significant contribution within the EoR.

A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

“…We focus on compact sources in this study, because we are interested in sources dominated by the central BH radiation. We note that the UV luminosity function at the faint end (restframe UV magnitude m UV  24 mag, or M UV  − 22 mag in the absolute frame) is dominated by star-forming galaxies (Bowler et al 2021;Adams et al 2022;Harikane et al 2022a). In this sense, our morphology selection is only sensitive to a subsample of AGN populations at high redshift, the host galaxies of which are outshined by the central AGNs or have compact morphology.…”

“…Aside from pure AGN surveys, one possible alternative approach to find low-luminosity AGNs is to use samples of UV-selected galaxies. At redshift 4 < z < 6, the UV luminosity functions of AGNs and Lyman break galaxies (LBGs) intersect with each other at M UV ∼ −23 mag (Matsuoka et al 2018;Ono et al 2018;Stevans et al 2018;Adams et al 2022;Harikane et al 2022a;Li et al 2022). Spectroscopic follow-up studies of z  4 LBGs have recently found several Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.…”

“…No AGNs have been confirmed yet (Morishita et al 2020;Fujimoto et al 2022;Jiang et al 2022), but with a few candidates at z = 7-8 (Ishikawa et al 2022). A naive interpretation of their low success rates is that their pointsource selection is not an effective approach to search for lowluminosity AGNs, because host-galaxy contamination becomes more severe (Bowler et al 2021;Adams et al 2022). On the other hand, a fraction of high-redshift quasars seem to have compact (<1 kpc) host galaxies, according to recent Atacama Large Millimeter/submillimeter Array observations of luminous z > 6 quasars (Neeleman et al 2021;Walter et al 2022).…”

Opening the Era of Quasar-host Studies at High Redshift with JWST

“…This step requires a recalibration to correct the original flux based on preflight measurements. A significant difference (10%-20% flux level) between the preflight and postflight photometric reference files is noted and mentioned in Adams et al (2022). We have updated our calibration for the F410M and F444W flux densities based on this information.…”