J/ApJS/276/72 The HETEDEX AGN catalog 4th data release (HDR4) (Liu+, 2025) ================================================================================ The Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) Active Galactic Nuclei Catalog: The Fourth Data Release. Liu C., Gebhardt K., Mentuch Cooper E., Davis D., Schneider D.P., Jarvis M.J., Farrow D.J., Finkelstein S.L., Chavez Ortiz O.A., The HETDEX Collaboration =2025ApJS..276...72L ================================================================================ ADC_Keywords: Active gal. nuclei; Spectra, optical; Surveys; Redshifts; Equivalent widths; Magnitudes Keywords: Active galactic nuclei Abstract: We present the active galactic nuclei (AGN) catalog from the fourth data release (HDR4) of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). HETDEX is an untargeted spectroscopic survey. HDR4 contains 345,874 Integral Field Unit observations from 2017 January to 2023 August covering an effective area of 62.9deg2. With no imaging preselection, our spectroscopic confirmed AGN sample includes low-luminosity AGN, narrow-line AGN, and/or red AGN down to g~25. This catalog has 15,940 AGN across the redshifts of z=0.1~4.6, giving a raw AGN number density of 253.4deg^-2^. Among them, 10,499 (66%) have redshifts either confirmed by line pairs or matched to the Sloan Digital Sky Survey Quasar Catalog. For the remaining 5441 AGN, 2083 are single broad-line AGN candidates, while the remaining 3358 are single intermediate broad-line (full width at half-maximum, FWHM~1200km/s) AGN candidates. A total of 4060 (39%) of the 10,499 redshift-confirmed AGN have emission-line regions 3{sigma} more extended than the image quality, which could be strong outflows blowing into the outskirts of the host galaxies or ionized intergalactic medium. Description: The Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) is an untargeted spectroscopic survey aiming at mapping the 1.884 usually indicates issues) (chi2fib_pipe) 585- 590 F6.2 arcsec SepDR16Q [0.01/3.5]?=999 Separation between the matched SDSS DR16Q AGN (rsep_dr16q) 592- 603 F12.6 --- zDR16Q [0.08/6.4]? Redshift of the matched SDSS DR16Q AGN (z_dr16q) 605- 622 A18 --- SDSS SDSS DR16Q AGN identifier (HHMMSS.ss+DDMMSS.s; J2000) (sdssid_dr16q) 624 I1 --- f_SDSS [0/1] Flag on SDSS (0=not in SDSS DR16Q) (sdss_flag) -------------------------------------------------------------------------------- Note (1): The R.A. and decl. of the emission-line flux-weighted FoF center of all member detections of a given AGN (J2000). If more than one line is present within the HETDEX wavelength range, only the strongest line is used as the weight. The FoF grouping method to remove duplicates from the 63,827 AGN detection sample is detailed in Section 4. Note (2): Method flag as follows: 1 = the single broad-line (sBL) search, see Section 3.3.2 2 = AGN identified by the LP mehod, see Section 3.3.1 3 = the crossmatch with SDSS DR16Q method; see Section 3.3.3 0 = AGN are identified by old versions of the AGN selection code Note (3): The R.A. and decl. of detectid_best. The position can be slightly off from the FoF center as the spatial detection search resolution is 0.15" (Section 3.1). Note (4): The HETDEX g-band magnitude and its 68% confidence interval calculated by multiplying the 1D spectrum of detectid_best with the SDSS g filter's throughput curve using ELiXer. Note (5): The throughput of shotid. This parameter is described in Gebhardt+ (2021ApJ...923..217G). Basically, it is defined as the nominal throughput treating each exposure as if it were 360s long through a 50m2 clear aperture. Throughput varies at different wavelengths. The typical throughput at 4540{AA} of our AGN sample is 0.15. In this paper, we require the throughput to be greater than 0.08 for an observation to be included in the catalog. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Emmanuelle Perret [CDS] 31-Oct-2025