J/ApJS/267/36 Low-redshift SDSS type 2 AGNs with var. from CSS. I. (Zhang, 2023)
Systematic research of low-redshift optically selected SDSS type 2 AGNs but with
apparent long-term optical variabilities from Catalina Sky Survey.
I. Data sample and basic results.
Zhang X.
<Astrophys. J. Suppl. Ser., 267, 36 (2023)>
=2023ApJS..267...36Z 2023ApJS..267...36Z
ADC_Keywords: Active gal. nuclei; Redshifts; Spectra, optical; Photometry;
Surveys
Keywords: Active galactic nuclei ; Active galaxies ; Emission line galaxies ;
Seyfert galaxies
Abstract:
The main objective of this article, the first in a dedicated series,
is to report basic results on systematic research of low-redshift
optically selected SDSS Type 2 active galactic nuclei (AGNs) but with
apparent optical variabilities. For all the pipeline-classified Type 2
AGNs in SDSS DR16 with z<0.3 and signal-to-noise ratio >10, long-term
optical V-band light curves are collected from the Catalina Sky
Survey. Through all light curves described by a damped random walk
process with process parameters of σ/(mag/days0.5) and
τ/days, 156 Type 2 AGNs have apparent variabilities with process
parameters at least 3 times larger than corresponding uncertainties
and with ln(σ/(mag/days0.5))>-4, indicating central AGN
activity regions directly in the line of sight, leading the 156 Type 2
AGNs as misclassified Type 2 AGNs. Furthermore, based on spectroscopic
emission features around Hα, 31 out of the 156 AGNs have broad
Hα, indicating the 31 Type 2 AGNs are actually Type 1.8 and/or
1.9 AGNs. Meanwhile, 14 out of the 156 AGNs have multiepoch SDSS
spectra. After checking multiepoch spectra of the 14 objects, no clues
for appearance and/or disappearance of broad lines indicates true
Type 2 AGNs rather than changing-look AGNs are preferred in the
collected Type 2 AGNs with long-term variabilities. Moreover, a small
sample of Type 2 AGNs have long-term variabilities with features
roughly described by theoretical tidal disruption events (TDEs)
expected t-5/3, indicating probable central TDEs as further and
strong evidence to support true Type 2 AGNs.
Description:
As well described in the homepage of the Catalina Sky Survey (CSS) and
in Drake+ (2009, J/ApJ/696/870), the three CSS telescopes are located
in the Santa Catalina Mountains just north of Tucson, Arizona. The
1.5m Cassegrain telescope (field of view about 5.0deg2) is located
on the 9157 foot summit of Mount Lemmon, alongside the 1.0m telescope
(field of view about 0.3deg2). The 0.7m Schmidt telescope (field of
view about 19.4deg2) is located on Mount Bigelow, just east of Mount
Lemmon. The CSS telescopes operate 24 nights per lunation with a 4-5d
break surrounding the full moon. The CSS database encompasses about
10yr long photometry for more than 500 million objects with V
magnitudes between 11.5 and 21.5 from an area of 33000deg2.
Based on R.A. and decl. of the collected 14354 SDSS-DR16 Type 2 AGNs,
long-term light curves can be collected and downloaded from
http://nesssi.cacr.caltech.edu/DataRelease/ for 12881 out of the
collected 14354 SDSS Type 2 AGNs, with searching radius of 3".
See Section 3.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 112 156 Basic information of the 156 Type-2 AGN with
apparent long-term variabilities
table2.dat 106 156 Line parameters of the 156 Type-2 AGN with
apparent long-term variabilities
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/MNRAS/441/1186 : Cataclysmic variables from CRTS (Drake+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/438/557 : BLR-less AGNs in Stripe82 (Zhang, 2014)
J/ApJS/219/1 : Catalog of Type-1 AGNs from SDSS-DR7 (Oh+, 2015)
J/MNRAS/455/2918 : Phot. & line luminosities for ASASSN-14li (Holoien+, 2016)
J/ApJS/229/39 : Narrow line Seyfert 1 gal. from SDSS-DR12 (Rakshit+, 2017)
J/ApJ/878/11 : Type 1 vs 2 X-ray COSMOS AGNs & environment (Zou+, 2019)
J/ApJ/896/10 : NSA low-mass gal. with PTF obs. (Baldassare+, 2020)
J/MNRAS/499/6053 : Indiv. opt. var. of AGNs from MEXSAS2 (Laurenti+, 2020)
J/ApJ/933/180 : TDSS. Changing-look quasars candidates (Green+, 2022)
http://nesssi.cacr.caltech.edu/DataRelease/ : The Catalina Surveys DR2 home
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Sp-ID SDSS DR16 plate-mjd-fiberid identifier
17- 21 F5.3 --- zspec [0/0.4] SDSS DR16 spectroscopic redshift
23- 40 A18 --- Name SDSS DR16 coordinate based name
(Jhhmmss.s±ddmmss.s) (G1)
42- 46 F5.2 mag m1 [11.5/18.5] Mean photometric magnitude
of the CSS light curve
48- 52 F5.2 mag m2 [13.2/25.2] SDSS DR16 photometric g-band
Petrosian magnitude
54- 59 F6.3 [10-7W] logLO3 [0/42.1] log, [OIII] luminosity, erg/s
61- 64 F4.2 [10-7W] e_logLO3 [0.01/0.2] Uncertainty in logLO3
66- 71 F6.3 [-] logO3HB [-0.53/1.4] log, Flux [OIII]5006Å
relative to Flux Hβ
73- 77 F5.3 [-] e_logO3HB [0.01/0.851] Uncertainty in logO3HB
79- 85 F7.4 [-] logN2HA [-0.41/0.44] log, Flux [NII]6583Å
relative to Flux Hα
87- 91 F5.3 [-] e_logN2HA [0.006/0.4] Uncertainty in logN2HA
93- 97 F5.2 [mag-1.d-0.5] lnsigma [-3.7/-0.97] natural log,
σ/mag/sqrt(day)
99-102 F4.2 [mag-1.d-0.5] e_lnsigma [0.09/0.6] Uncertainty in lnsigma
104-107 F4.2 [d-1] lntau [2.8/7.2] natural log, τ/day
109-112 F4.2 [d-1] e_lntau [0.12/1.5] Uncertainty in lntau
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Sp-ID SDSS DR16 plate-mjd-fiberid
identifier (G1)
17- 18 A2 --- f_Sp-ID Flag on Sp-ID (1)
20- 23 F4.2 0.1nm sig-NII1 [1.2/6.1] Second moment, first
component, [NII]6583Å, Angstroms
25- 28 F4.2 0.1nm e_sig-NII1 [0.01/1.3] Uncertainty in sig-NII1
30- 33 I4 10-20W/m2 flux-NII1 [11/4012] Flux, first component,
[NII]6583Å, 10-17erg/s/cm2
35- 37 I3 10-20W/m2 e_flux-NII1 [1/191] Uncertainty in flux-NII1
39- 43 F5.2 0.1nm sig-NII2 [2.36/11]? Second moment, second
component, [NII]6583Å, Angstroms (2)
45- 48 F4.2 0.1nm e_sig-NII2 [0/2]? Uncertainty in sig-NII2 (2)
50- 53 I4 10-20W/m2 flux-NII2 [36/1488]? Flux, second component,
[NII]6583Å, 10-17erg/s/cm2 (2)
55- 57 I3 10-20W/m2 e_flux-NII2 [8/147]? Uncertainty in flux-NII2 (2)
59- 62 F4.2 0.1nm sig-Ha1 [1.38/9.1] Second moment, first
component, Hα, Angstroms
64- 67 F4.2 0.1nm e_sig-Ha1 [0.02/2.4] Uncertainty in sig-Ha1
69- 72 I4 10-20W/m2 flux-Ha1 [10/3751] Flux, first component,
Hα, 10-17erg/s/cm2
74- 76 I3 10-20W/m2 e_flux-Ha1 [1/150] Uncertainty in flux-Ha1
78- 83 F6.2 0.1nm sig-Ha2 [1.4/103]? Second moment, second
component, Hα, Angstroms (2)
85- 88 F4.2 0.1nm e_sig-Ha2 [0.07/9]? Uncertainty in sig-Ha2 (2)
90- 93 I4 10-20W/m2 flux-Ha2 [37/4705]? Flux, second component,
Hα, 10-17erg/s/cm2 (2)
95- 97 I3 10-20W/m2 e_flux-Ha2 [4/391]? Uncertainty in flux-Ha2 (2)
99- 102 F4.2 --- chi2 [0.28/4.1] Determined χ2 (3)
104- 106 A3 --- bHa Broad Hα components?
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Note (1):
** = the unique spectroscopic features in SDSS 1870-53383-0466 with
different redshifts from emission lines and from absorption features.
Note (2): Null values for the second component means no reliable
parameter which is three times smaller than its corresponding
uncertainty.
Note (3): determined χ2 calculated by the summed squared
residuals divided by degree of freedom related to the best
fitting results to the emission lines.
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Global notes:
Note (G1): There are three objects with multiple-epoch SDSS spectra
listed in the complete Table: J001558.2-001812.6
(0390-51816-0305, 0390-51900-0306), J030349.1-010613.4
(0411-51817-0217, 0411-51873-0203) and J115601.1+001237.9
(0284-51662-0558, 0284-51943-0551).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Nov-2023