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

Abstract

We present the Lyα 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. The AGN are selected either by emission line pairs characteristic of AGN or by a single broad emission line, free of any photometric preselections (magnitude/color/morphology). The sample consists of 2346 AGN spanning 1.88 < z < 3.53, covering an effective area of 30.61 deg2. Approximately 2.6% of the HETDEX AGN are not detected at >5σ confidence at r ∼ 26 in the deepest r-band images we have searched. The Lyα line luminosity ranges from ∼1042.3 to 1045.9 erg s−1. Our Lyα LF shows a turnover luminosity with opposite slopes on the bright end and the faint end: The space density is highest at L Ly α ∗ = 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 Å monochromatic luminosity of the power-law component of the continuum (M1450) 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 and density evolution model: the turnover luminosity ( M 1450 * ) increases, and the turnover density (Φ*) decreases with increasing redshift.

The Stellar Mass–Black Hole Mass Relation at z ∼ 2 down to  BH ∼

“…These 2346 type 1 AGNs spans a redshift range of 1.88-3.53. The UV luminosity function of the HETDEX type 1 AGN is comparable with previous results at similar redshifts while extending to a rest-frame UV continuum magnitude of −21, three magnitudes fainter than previous results (Zhang et al 2021;Liu et al 2022b).…”

“…From the HETDEX type 1 AGN catalog presented in Liu et al (2022a), we select objects that: (a) are located in the SHELA field, and (b) have redshifts of z = 2.0-2.5 and broad (FWHM > 1000 km s −1 ) C IV emission lines with emission line fluxes greater than 2 × 10 −16 erg s −1 cm 2 that correspond to the 50% detection limit of typical broad emission lines in the HETDEX spectra (Liu et al 2022b). Because C IV emission line profiles of type 1 AGNs may show absorption features and affect the line profile fitting, we further require the fitting results of C IV emission lines to have χ 2 values smaller than 4 and conduct visual inspection to exclude the objects with bad fitting results.…”

“…We adopt the parameters (A,B) of (6.66, 0.53) from Vestergaard & Peterson (2006). We use the C IV line widths from the HETDEX AGN catalog (Liu et al 2022b) and account for the instrumental broadening (Gebhardt et al 2021;Hill et al 2021). For L 1350 , we take the AGN components of the best-fit SED derived in Section 3.…”

“…We adopt the parameters (A,B) of (6.66, 0.53) from Vestergaard & Peterson (2006). We use the C IV line widths from the HETDEX AGN catalog (Liu et al 2022b)…”

“…HETDEX utilizes the VIRUS wide-field spectrograph (Hill et al 2021) on the upgraded 10 m Hobby-Eberly Telescope (HET; Ramsey et al 1998;Hill et al 2021). AGNs detected in the HETDEX survey include faint type 1 AGNs that potentially host SMBHs with low BH  (Zhang et al 2021;Liu et al 2022aLiu et al , 2022b. Utilizing multiband archival photometry in the Spitzer-HETDEX Exploratory Large-area (SHELA) survey field (Papovich et al 2016), we perform host-nuclear decomposition with SED fitting and derive  * .…”