J/A+A/704/A343 Re-classification of high-redshift QSOs (Meusinger, 2025)
A treasure hunt in the pool of spectra classified as high-redshift QSOs by the
spectroscopic pipeline of the SDSS DR16.
Meusinger H.
<Astron. Astrophys. 704, A343 (2025)>
=2025A&A...704A.343M 2025A&A...704A.343M (SIMBAD/NED BibCode)
ADC_Keywords: Spectra, optical ; Galaxies, spectra ; QSOs ; Spectral types ;
Stars, white dwarf ; Supernovae
Keywords: binaries: symbiotic - stars: magnetic field - galaxies: evolution -
quasars: absorption lines - quasars: emission lines - quasars: general
Abstract:
The discovery of outsiders in the form of unusual, rare, or even
unknown object types is important as they can provide useful
information about otherwise hidden physical phenomena and processes.
The present study takes advantage of the fact that the automated
spectroscopic pipeline of the Sloan Digital Sky Survey (SDSS)
occasionally assigns uncommon spectra to high-redshift quasi-stellar
objects (QSOs). This study presents an analysis of about 4000 spectra
that are QSOs with redshifts z>4.5 according to the spectroscopic
pipeline of the Sloan Digital Sky Survey (SDSS) DR16. It turns out
that, after excluding non-classifiable spectra of low quality and
those from three special plates, only 26% are high-z QSOs, 50% are
QSOs at lower redshifts, 16% are galaxies, and 8% are stars. A
significant proportion of the latter three categories prove to be
unusual and are re-assigned here to a variety of rare spectral types.
The results of the re-evaluation are summarised in the catalogue.
Description:
The table contains 3955 spectra from 3351 sources classified by the
SDSS DR16 as high-redshift QSOs. The list was constructed via sql
query from the SDSS DR16 and contains the sources with z>4.5, and
with zWarning=0 (means all is well) or zWarning=64 (negative fluxes).
All spectra were re-classified (type, subtype, redshift, and remarks)
using the tool zshift.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 165 3955 Re-classified apparent high-z QSOs
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See also:
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/3955] Running catalogue number
7- 14 F8.4 deg RAdeg Right ascension (J2000)
16- 23 F8.4 deg DEdeg Declination (J2000)
25- 45 A21 --- Name Name of spectrum (spect-plate-mjd-fiber)
48- 66 A19 --- Target SDSS target type
68 I1 --- Nsp Number of spectra at this position
71- 76 F6.4 --- zSDSS Spectroscopic redshift from SDSS
78- 85 F8.4 --- e_zSDSS []?=-1 Redshift error from SDSS
87- 91 A5 --- Survey Survey name
93- 95 A3 --- Class Spectroscopic class from SDSS
97-105 A9 --- Subclass Spectroscopic subclass from SDSS
108-113 F6.4 --- zQC ?=- Redshift from DR16Q (1)
114-118 F5.3 --- zHere ?=- Redshift from present study
121 I1 --- rzHere [0/5] Estimated reliability of
new redshift (2)
124 I1 --- Selected [0/1] selected as best version of SDSS
spectrum at this location among SDSS
plates according to present study
126-132 A7 --- Type Spectroscopic type (3)
134-140 A7 --- Subtype Spectroscopic subtype (4)
142-148 A7 --- BadQuality Remark on bad quality (5)
150-165 A16 --- Remark Remarks (6)
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Note (1): The Sloan Digital Sky Survey Quasar Catalog: sixteenth data release
(DR16Q), Lyke et al. (2020ApJS..250....8L 2020ApJS..250....8L, Cat. VII/289).
Note (2): Estimated reliability of new redshift as follows:
3 = good
2 = reasonable
1 = uncertain
0 = unclear
Note (3): Spectroscopic type as follows:
QSO = typical (broad) QSO emission and/or absorption lines
galaxy = no indication of typical QSO lines
star = typical stellar absorption lines or narrow emission lines at z=0
unknown = no classifiable spectral features
Note (4): Spectroscopic subtype as follows:
3ABQ = 3000Å break QSO
ALs = absorption lines
C = Carbon star
ELs = emission lines
FeLoBAL = FeLoBAL QSO
HiBAL = HighBAL QSO
LoBAL = LowBAL QSO
LT = late-type star
sdB = subdwarf B star
SN = supernova
type2 = narrow-emission line QSO (type 2)
WD = white dwarf (spectral type, if known, in parenthesis)
WDLT = white dwarf plus late-type star
WLQ = QSO with weak emission lines
Note (5): Remark on bad quality as follows:
corrupt = corrupted spectrum (e.g. substantial part missing)
noisy = noisy spectrum without identifiable lines
spike = superimposed by diffraction spike of nearby bright star
Note (6): Remarks as follows:
AALs = associated absorption lines
AsBLs = asymmetric Balmer lines
CyHs = cyclotron humps in stellar spectrum
DBR = displacement between blue and red part
DLAS = damped Lyman alpha system
DLs = double narrow emission lines
DPBLs = double-peaked broad Balmer lines
Fe-em = strong Fe II emission
FeIII-em = strong Fe III emission
GP = possibly Gunn-Petterson trough
HBD = high Balmer decrement
IALs = absorption lines from intermediate absorber
Lya-abs = Lyman alpha emission line significantly absorbed
MATs = many absorption troughs
NBO = nearby bright object
NBS = blue part of the spectrum dominated by nearby blue source
NERP = example of non-genuine emission peak near the red edge
PM = significant proper motion (Gaia DR3)
PSB = post-starburst
red = unusually red continuum
RWA = red wing of emission line absorbed
SELs = star with remarkably strong emission lines
sLya = very strong Lyman alpha emission line
UC = unusual continuum
unusual = spectral type identified, but unusual
special notes:
(1) = unusual: broad MgII, but not CIV
(2) = superimposed by emission line galaxy SDSS J004846.29-004612.8 at z=0.939
(3) = similar to spec-0339-51692-0524
(4) = broad [OIII]5007 line
(5) = superimposed by emission line system at z=0 (special plate SF region
Taurus-Orion)
(6) = superimposed by emission line system (Ha) at z=0.159
(7) = blending a background galaxy at z=0.364
(8) = broad absorption lines
(9) = gravitationally lensed (J03)
(10) = superimposed by star (most likely WD)
(11) = most likely absorption line galaxy at z=0.597, blended by emission line
galaxy at z=0.177
(12) = unusual Lyman limit
(13) = unidentified broad absorption troughs at 6735, 5390Å
(14) = remarkable combination of type2 + FeLoBAL
(15) = unidentified broad absorption troughs at 6387, 5119Å
(16) = red part from absorption line galaxy at z=0.557
(17) = changing-look AGN (P24)
literature:
E06 = Eisenstein et al. (2006ApJS..167...40E 2006ApJS..167...40E. Cat. J/ApJS/167/40)
G11 = Girven et al. (2011MNRAS.417.1210G 2011MNRAS.417.1210G, Cat. J/MNRAS/417/1210)
J03 = Johnston et al. (2003AJ....126.2281J 2003AJ....126.2281J)
K13 = Kleinman et al. (2013ApJS..204....5K 2013ApJS..204....5K, Cat. J/ApJS/204/5)
K15 = Kepler et al. (2015MNRAS.446.4078K 2015MNRAS.446.4078K, Cat. J/MNRAS/446/4078)
K16 = Kepler et al. (2016MNRAS.455.3413K 2016MNRAS.455.3413K, Cat. J/MNRAS/455/946)
M08 = Mickaelian et al. (2008AJ....136..946M 2008AJ....136..946M, Cat. III/258)
P24 = Panda et al. (2024ApJS..272...13P 2024ApJS..272...13P, Cat. J/AJ/272/13)
R16 = Rebassa-Mansergas et al. (2016MNRAS.458.3808R 2016MNRAS.458.3808R, Cat. J/MNRAS/458/3808)
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Acknowledgements:
Helmut Meusinger, meus(at)tls-tautenburg.de
(End) Helmut Meusinger [TLS, Germany], Patricia Vannier [CDS] 22-Sep-2025