The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) II. Luminosity Function

TL;DR

This paper presents the LyA emission line luminosity function of AGN from the HETDEX survey, revealing a turnover luminosity and its evolution over redshift, providing insights into AGN luminosity distribution and evolution.

Contribution

It introduces a new LyA luminosity function for AGN from HETDEX data, analyzing its shape and evolution across redshifts without photometric pre-selection.

Findings

The LyA luminosity function shows a turnover with opposite slopes on bright and faint ends.

The UV luminosity functions indicate the highest AGN space density at the turnover luminosity.

The luminosity function evolution is well-described by a LEDE model across redshift bins.

Abstract

We present the LyA emission line luminosity function (LF) of the Active Galactic Nuclei (AGN) in the first release of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) AGN catalog (Liu et al. 2022, Paper I). The AGN are selected either by emission-line pairs characteristic of AGN or by single broad emission line, free of any photometric pre-selections (magnitude/color/morphology). The sample consists of 2,346 AGN spanning 1.88<z<3.53, covering an effective area of 30.61 deg^2. Approximately 2.6 of the HETDEX AGN are not detected at $>5\sigma$ confidence at r~26 in the deepest $r$-band images we have searched. The LyA line luminosity ranges from ~10^42.3 to ~10^45.9 erg s^-1. Our LyA LF shows a turnover luminosity with opposite slopes on the bright end and the faint end: The space density is highest at L_LyA^*=10^43.4 erg s^-1. We explore the evolution of the AGN LF over a broader redshift range (0.8<z<3); constructing the rest-frame ultraviolet (UV) LF with the 1450 AA monochromatic luminosity of the power-law component of the continuum ($\rm M_{1450}$) from M_1450~-18 to ~-27.5. We divide the sample into three redshift bins (z~1.5, 2.1, and 2.6). In all three redshift bins, our UV LFs indicate that the space density of AGN is highest at the turnover luminosity M_1450^* with opposite slopes on the bright end and the faint end. The M_1450 LFs in the three redshift bins can be well-fit with a luminosity-evolution-density-evolution (LEDE) model: the turnover luminosity (M_1450^*) increases and the turnover density (Phi^*) decreases with increasing redshift.