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
<Astrophys. J. Suppl. Ser., 276, 72 (2025)>
=2025ApJS..276...72L 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 3σ
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 1.88<z<3.52
Universe and measuring its expansion rate to 1% precision by providing
the redshifts of one million Lyα emitters (LAEs) over 540deg2.
The untargeted spectroscopic observations with no imaging
preselections are acquired by the Visible Integral field Replicable
Unit Spectrograph (VIRUS). VIRUS has 78 51"x51" IFUs spanning the
central 18 field of view of the 22 focal plane on the 10m Hobby-Eberly
Telescope (HET). The survey began from 2017 January with 16 IFUs
mounted. IFUs were installed on the telescope gradually. All IFUs were
completed with their installation in 2021 August. Each IFU bundle
consists of 448 1.5" diameter fibers. Upon completion, each HETDEX
exposure collects 34,944 fiber spectra. The survey was recently
completed with all observations in 2024 August. The spectral coverage
is from 3500 to 5500Å with the resolving power of R∼800.
Observations of HETDEX Data Release 4 (HDR4) were completed in
2023 August with the full survey 72% completed. This paper describes
the HETDEX HDR4 AGN catalog.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
hdr4.dat 624 15940 HETDEX HDR4 AGN catalog
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Description of file:
hetdexagnhdr4.fits is the original FITS file as downloaded on:
http://web.corral.tacc.utexas.edu/hetdex/HETDEX/catalogs/agn_catalog_v2.0/
or in the tar.gz package of the journal
See also:
I/317 : The PPMXL Catalog (Roeser+ 2010)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/457/79 : VIMOS VLT Deep Survey: faint type-1 AGN (Gavignaud+, 2006)
J/ApJ/943/177 : HETDEX Public Source Cat. (Version 3.2) (Mentuch Cooper+, 2023)
http://hetdex.org/ : HETDEX homepage
Byte-by-byte Description of file: hdr4.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [0/15939] Running sequence number
(agnid)
7- 15 F9.5 deg RAdeg [5.9/335.1] FoF center right
ascension (J2000) (ra) (1)
17- 26 F10.6 deg DEdeg [-2.5/68] FoF center declination
(J2000) (dec) (1)
28- 34 F7.5 --- z [0.085/4.61] Redshift (z)
36- 43 F8.6 --- e_z [0/0.009] z uncertainty (z_err)
45 I1 --- f_z [0/1] Flag on z (1=confirmed z)
(zflag)
47 I1 --- f_Seq [0/1] Flag on Seq (1=confirmed AGN)
(agn_flag)
49 I1 --- Meth [0/3]? Method flag (sflag) (2)
51- 60 A10 --- Field Field name in the HETDEX survey
(field)
62- 63 I2 --- Nshot [0/15] Number of the observed
shots of (R.A., decl.) (nshot)
65- 66 I2 --- Nmem [1/96] Number of member detectids
(nmem)
68- 77 I10 --- BestDet [3000035705/4090574155] Detectid
closest to the FoF center
(detectid_best)
79- 87 F9.5 deg RABdeg Right ascension (J2000) of BestDet
(ra_best) (3)
89- 98 F10.6 deg DEBdeg Declination (J2000) of BestDet
(dec_best) (3)
100- 107 F8.6 arcsec roff [0/2.2] Offset between
RABdeg,DEBdeg with FoF center
(roff)
109- 115 F7.4 mag gmag [16.3/32.5] HETDEX g-band
magnitude measured at
RABdeg,DEBdeg (maggwide) (4)
117- 125 F9.4 mag e_gmag [0/999]? Uncertainty on gmag
(maggwide_err) (4)
127- 164 A38 --- fiberid ID of the fiber that is closest to
BestDet (fiberid)
166- 176 I11 --- shotid [20170126002/20230826016] ID of
the shot for BestDet (shotid)
178- 197 A20 --- multiframe IFU for BestDet (multiframe)
199- 204 F6.4 --- TghPut [0.08/0.6] Throughput of shotid
(throughput) (5)
206- 212 F7.5 arcsec FWHM-virus [1.2/3.2] Image quality (FWHM) of
shotid (fwhm_virus)
214- 221 F8.6 arcsec e_FWHM-virus [0/0.99] FWHM-virus uncertainty
(fwhmviruserr)
223- 229 F7.3 --- apcor [-99/0.99] Aperture correction of
BestDet
(a value of 1 means no correction)
(apcor)
231- 237 F7.2 0.1nm LamObsElix [3476.6/5530.6] Observed line
wavelength fit by ELIXER
(wobs_elixer)
239- 247 F9.6 0.1nm e_LamObsElix [0/11.4] LamObsElix uncertainty
(wobserrelixer)
249- 260 E12.6 10-17mW/m2 FLya [0/17659]?=-99 Rest-frame flux of
the Lyaλ1215 emission
(flux_LyA)
262- 272 F11.6 --- SNRLya [0/350]? SNR of Lya (snr_LyA)
274- 285 E12.6 km.s-1 FWHMLya [0/22328]? Rest-frame FWHM of the
LyA emission (fwhm_LyA)
287- 298 E12.6 0.1nm EWLya [0/28020]? Rest-frame EW of the
LyA emission (ew_LyA)
300- 311 E12.6 10-17mW/m2 FCIV [0/16457]?=-198 Rest-frame flux of
the CIVλ1549 emission
(flux_CIV)
313- 324 E12.6 --- SNRCIV [-99/226]? SNR of CIV (snr_CIV)
326- 337 E12.6 km.s-1 FWHMCIV [0/19355]? Rest-frame FWHM of the
CIV emission (fwhm_CIV)
339- 350 E12.6 0.1nm EWCIV [-449/2.6e+15]?=-99 Rest-frame EW
of the CIV emission (ew_CIV)
352- 363 E12.6 10-17mW/m2 FCIII [0/6615]?=-198 Rest-frame flux of
the CIII]λ1909 emission
(flux_CIII)
365- 376 E12.6 --- SNRCIII [-99/123]? SNR of CIII (snr_CIII)
378- 389 E12.6 km.s-1 FWHMCIII [0/15670]? Rest-frame FWHM of the
CIII emission (fwhm_CIII)
391- 402 E12.6 0.1nm EWCIII [-3.9/1.8e+15]? Rest-frame EW of
the CIII emission (ew_CIII)
404- 415 E12.6 10-17mW/m2 FMgII [0/6738]?=-198 Rest-frame flux of
the MgII]λ2799 emission
(flux_MgII)
417- 428 E12.6 --- SNRMgII [-99/155]? SNR of MgII (snr_MgII)
430- 441 E12.6 km.s-1 FWHMMgII [0/10663]? Rest-frame FWHM of the
MgII emission (fwhm_MgII)
443- 454 E12.6 0.1nm EWMgII [-8.2/9999]? Rest-frame EW of the
MgII emission (ew_MgII)
456- 467 E12.6 10-17mW/m2 FOVI [0/7587]?=-198 Rest-frame flux of
the OVIλ1034 emission
(flux_OVI)
469- 480 E12.6 --- SNROVI [-99/233]? SNR of OVI (snr_OVI)
482- 493 E12.6 km.s-1 FWHMOVI [0/29015]? Rest-frame FWHM of the
OVI emission (fwhm_OVI)
495- 506 E12.6 0.1nm EWOVI [-36/7.7e+14]? Rest-frame EW of
the OVI emission (ew_OVI)
508- 519 E12.6 0.1nm LamPipe [3485.8/5530.6]?=0 Observed line
wavelength from the HETDEX
pipeline (wave_pipe)
521- 532 E12.6 10-17mW/m2 FPipe [0/2071] Observed line flux from
the HETDEX pipeline (flux_pipe)
534- 544 F11.6 10-17cW/m2/nm ContPipe [-12.5/224] Observed continuum
from the HETDEX pipeline
(continuum_pipe)
546- 554 F9.6 0.1nm sigmaPipe [0/50] Observed sigma from the
pipeline's single Gaussian fit
(linewidth_pipe)
556- 565 F10.6 --- SNRPipe [0/186] SNR from the pipeline's
single Gaussian fit (sn_pipe)
567- 574 F8.6 --- chi2Pipe [0/6] Chi2 from the pipeline's
single Gaussian fit (chi2_pipe)
576- 583 F8.6 --- chi2fibPipe [0/9.8] Chi2 of fit to 2D spectrum
for each fiber
(>4 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)
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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 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 4540Å 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.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 31-Oct-2025