J/ApJ/933/180 TDSS. Changing-look quasars candidates (Green+, 2022)
The Time Domain Spectroscopic Survey:
Changing-look Quasar Candidates from Multi-epoch Spectroscopy in SDSS-IV.
Green P.J., Pulgarin-Duque L., Anderson S.F., Macleod C.L., Eracleous M.,
Ruan J.J., Runnoe J., Graham M., Roulston B.R., Schneider D.P., Ahlf A.,
Bizyaev D., Brownstein J.R., Del Casal S.J., Dodd S.A., Hoover D., Matt C.,
Merloni A., Pan K., Ramirez A., Ridder M.
<Astrophys. J., 933, 180-180 (2022)>
=2022ApJ...933..180G 2022ApJ...933..180G (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Active gal. nuclei ; Redshifts ; Optical ; Ultraviolet
Keywords: Accretion - Quasars - Active galactic nuclei -
Variable radiation sources - Catalogs
Abstract:
Active galactic nuclei (AGN) can vary significantly in their
rest-frame optical/UV continuum emission, and with strong associated
changes in broad line emission, on much shorter timescales than
predicted by standard models of accretion disks around supermassive
black holes. Most such changing-look or changing-state AGN-and at
higher luminosities, changing-look quasars (CLQs)-have been found via
spectroscopic follow-up of known quasars showing strong photometric
variability. The Time Domain Spectroscopic Survey of the Sloan Digital
Sky Survey IV (SDSS-IV) includes repeat spectroscopy of large numbers
of previously known quasars, many selected irrespective of photometric
variability, and with spectral epochs separated by months to decades.
Our visual examination of these repeat spectra for strong broad line
variability yielded 61 newly discovered CLQ candidates. We
quantitatively compare spectral epochs to measure changes in continuum
and Hβ broad line emission, finding 19 CLQs, of which 15 are
newly recognized. The parent sample includes only broad line quasars,
so our study tends to find objects that have dimmed, i.e., turn-off
CLQs. However, we nevertheless find four turn-on CLQs that meet our
criteria, albeit with broad lines in both dim and bright states. We
study the response of Hβ and Mg II emission lines to continuum
changes. The Eddington ratios of CLQs are low, and/or their Hβ
broad line width is large relative to the overall quasar population.
Repeat quasar spectroscopy in the upcoming SDSS-V black hole Mapper
program will reveal significant numbers of CLQs, enhancing our
understanding of the frequency and duty cycle of such strong
variability, and the physics and dynamics of the phenomenon.
Description:
Our parent sample consists of a subset of objects classified as
quasars by the SDSS pipeline that appear in the SDSS Data Release 14
(DR14) quasar catalog (Paris et al., 2018, Cat. VII/286), which
included 526356 quasars. All the reduced and calibrated SDSS spectra
analyzed herein were publicly released as part of SDSS DR14, which
includes data through 2016 May 11. The SDSS-IV final quasar catalog
DR16 (Lyke et al., 2020, Cat. VII/289/) describes an additional 225082
new quasars, and additional epochs obtained for previously known SDSS
quasars.
Table 2 lists all 61 changing-look quasars (CLQ) candidates in our
visually selected DR14 quasar sample, their redshifts, spectral
epochs, and associated telescopes, along with best-fit modeled values
for their continuum luminosities at 2800, 3240, and 5100Å.
Emission line luminosities and their uncertainties are provided for
Hβ and MgII, where available.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 145 167 Changing-look quasars (CLQ) candidates in our
visually selected DR14 quasar sample
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- SDSS SDSS Identifier (JHHMMSS.ss+DDMMSS.ss)
22- 32 A11 --- Sel Selection (1)
34- 38 F5.3 --- zspec [0.05/0.9] SDSS spectroscopic redshift
40- 44 I5 d MJD [51811/58699] Spectrum epoch, JD-2400000.5
46- 51 A6 --- Fac Facility (2)
53- 58 F6.2 --- Nsigma [0.5/14.09]? Nσ, Broad Hβ
60 A1 --- State State (3)
62- 68 F7.2 10+35W L3240 [0.46/2075.5] Luminosity, continuum at
3240Å (in 10+42 erg/s unit)
70- 73 F4.1 10+35W e_L3240 Uncertainty in L3240
75- 80 F6.1 10+35W L5100 [2.5/1673.7] Luminosity, continuum at
5100Å (in 10+42 erg/s unit)
82- 85 F4.1 10+35W e_L5100 [0.1/88.8] Uncertainty in L5100
87- 91 F5.2 10+35W LHb Luminosity, Hβ emission
(in 10+42 erg/s unit)
93- 96 F4.2 10+35W e_LHb Uncertainty in LHb
98-105 F8.2 10+35W L2800 [0.77/2224.29]? Luminosity, continuum at
2800Å (in 10+42 erg/s unit)
107-112 F6.2 10+35W e_L2800 [0.01/63.52]? Uncertainty in L2800
114-119 F6.2 10+35W LMgII [0.05/41.54]? Luminosity, MgII emission
(in 10+42 erg/s unit)
121-125 F5.2 10+35W e_LMgII [0.05/9.73]? Uncertainty in LMgII
127-145 A19 --- Notes Notes and/or references (4)
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Note (1): CLQ Candidate Selection as follows (table 1):
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TDSS Target Type NQSOs NCand %Cand NCLQ %CLQ
--------------------------------------------------
A 17511 0 0.0 0 0
B 44832 1 0.0 0 0
FES_DE 653 9 1.4 6 0.9
FES_HYPQSO 1237 23 2.0 4 0.3
FES_MGII 64 1 1.6 1 1.5
FES_NQHISN 744 2 0.3 2 0.3
RQS1 10520 18 0.2 5 0.0
RQS2 2243 1 0.0 1 0.0
RQS2v 1111 2 0.1 0 0.0
RQS3 1056 0 0 0 0
RQS3v 1579 4 0.3 0 0
Total 64039 61 0.1 19 0.03
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Note. Target selection methods for our TDSS CLQs. These abbreviations
correspond to several different target selection algorithms used for the TDSS
program of SDSS-IV, and are described briefly in Section 2. Some QSOs were
selected by TDSS using more than one method. Small number statistics dominate
the percentages listed, which are derived simply by dividing by NQSOs.
See the discussion in Section 2.
Note (2): Facility as follows:
Mag/L3 = Magellan ∼6.5m Clay/LDSS3
MMT/BC = MMT ∼6.5m/BlueChannel
MMT/BS = MMT ∼6.5m/BinoSpec
WHT = WHT ∼4.2m/ISIS
Note (3): Designated state as follows:
B = Bright
D = Dim
Note (4): Notes and references as follows:
CLQ = quasar when Nσ(Hβ)≥3 between the designated bright
and dim spectral epochs
TurnOn = CLQ brightened with time;
VIc = Nσ(Hβ)≥2 quasars where strong CLQ nature seems
evident upon visual inspection (see Figure 5);
M16c = MacLeod et al. (2016MNRAS.457..389M 2016MNRAS.457..389M],
CLQ based there on Nσ(Hβ)>3
M19c = MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M),
CLQ based on Nσ(Hβ)>3
M19v = MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M), CLQ based on VI only
M19n = MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M), candidate, not analyzed
M19r = MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M), rejected
H19 = Noted by Hutsemekers et al. (2019A&A...625A..54H 2019A&A...625A..54H)
as low (<1%) spectro-polarization
R18 = Noted by Rumbaugh et al. (2018ApJ...854..160R 2018ApJ...854..160R) as an
Extremely Variable Quasar (EVQ; Δg>1mag)
Y18 = CLQ noted by Yang et al. (2018ApJ...862..109Y 2018ApJ...862..109Y)
H20 = Homan et al. (2020MNRAS.496..309H 2020MNRAS.496..309H)
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Acknowledgements:
Jessica Krick, jkrick(at)caltech.edu
(End) Patricia Vannier [CDS] 27-Mar-2023