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. =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 {sigma}/(mag/days^0.5^) and {tau}/days, 156 Type 2 AGNs have apparent variabilities with process parameters at least 3 times larger than corresponding uncertainties and with ln({sigma}/(mag/days^0.5^)){>}-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 H{alpha}, 31 out of the 156 AGNs have broad H{alpha}, 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 5.0deg^2^) is located on the 9157 foot summit of Mount Lemmon, alongside the 1.0m telescope (field of view about 0.3deg^2^). The 0.7m Schmidt telescope (field of view about 19.4deg^2^) 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 33000deg^2^. 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: -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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]5006{AA} relative to Flux H{beta} 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]6583{AA} relative to Flux H{alpha} 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, {sigma}/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, {tau}/day 109-112 F4.2 [d-1] e_lntau [0.12/1.5] Uncertainty in lntau -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- 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]6583{AA}, 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]6583{AA}, 10^-17^erg/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]6583{AA}, 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]6583{AA}, 10^-17^erg/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, H{alpha}, 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, H{alpha}, 10^-17^erg/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, H{alpha}, 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, H{alpha}, 10^-17^erg/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 {chi}^2^ (3) 104- 106 A3 --- bHa Broad H{alpha} components? -------------------------------------------------------------------------------- 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 {chi}^2^ calculated by the summed squared residuals divided by degree of freedom related to the best fitting results to the emission lines. -------------------------------------------------------------------------------- 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). -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Nov-2023