J/MNRAS/438/557 BLR-less AGNs in Stripe82 (Zhang, 2014)
Optically selected BLR-less active galactic nuclei from the SDSS Stripe82
Database. I. The sample.
Zhang X.-G.
<Mon. Not. R. Astron. Soc., 438, 557-572 (2014)>
=2014MNRAS.438..557Z 2014MNRAS.438..557Z
ADC_Keywords: Active gal. nuclei ; Redshifts ; Photometry, SDSS
Keywords: galaxies: active - galaxies: nuclei - quasars: emission lines -
galaxies: Seyfert
Abstract:
This is the first paper in a dedicated series to study the properties
of the optically-selected broad-line-region-less (BLR-less) active
galactic nuclei (AGNs; with no-hidden central broad emission line
regions). We carried out a systematic search for the BLR-less AGNs
through the Sloan Digital Sky Survey Legacy Survey (SDSS Stripe82
Database). Based on the spectral decomposition results for all the 136
676 spectroscopic objects (galaxies and quasars) with redshift less
than 0.35 covered by the SDSS Stripe82 region, our spectroscopic
sample for the BLR-less AGNs includes 22 693 pure narrow line objects
without broad emission lines but with apparent AGN continuum emission
RAGN>0.3 and apparent stellar lights Rssp>0.3. Then, using the
properties of the photometry magnitude RMS (RMS) and Pearson's
coefficients (R1,2) between two different SDSS band light curves:
RMSk>3xRMSMk and R1,2≳0.8, the final 281 pure narrow line
objects with true photometry variabilities are our selected reliable
candidates for the BLR-less AGNs. The selected candidates with higher
confidence levels not only have the expected spectral features of the
BLR-less AGNs, but also show significant true photometry
variabilities. The reported sample enlarges at least four times the
current sample of the BLR-less AGNs, and will provide more reliable
information to explain the lack of the BLRs of AGNs in our following
studies.
Description:
In order to select the reliable candidates for the BLR-less AGNs
through both the photometry variabilities and the observed spectral
features, we apply the following procedures to the objects in the SDSS
Stripe82 Database. The emission line parameters should be first
determined, in order to confirm that our spectroscopic sample includes
the pure narrow line objects only (type 2 objects, the objects having
both strong and weak broad lines cannot be considered). Then, the SDSS
photometric light curves of the objects in the spectroscopic sample
should be carefully analysed to find the reliable candidates for the
BLR-less AGNs.
We use data from http://www.sdss3.org/dr8/spectro/spectro_access.php
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 67 281 Basic parameters of the 281 candidates for
the BLR-less AGNs
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See also:
J/A+A/525/A37 : SDSS Stripe 82 QSOs variability indexes (Meusinger+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- MJD MJD component of SDSS spectroscopic designation
6 A1 --- --- [-]
7- 10 I04 --- Plate Plate component of SDSS spectroscopic designation
11 A1 --- --- [-]
12- 14 I03 --- Fib Fiber component of SDSS spectroscopic designation
16- 20 F5.3 --- z [0.003/0.36] SDSS redshift
22- 31 F10.6 deg RAdeg Right ascension (J2000)
33- 41 F9.6 deg DEdeg Declination (J2000)
44- 47 F4.1 mag rmag [12/22]?=0 SDSS r magnitude
49- 52 F4.2 --- R [0/1] RAGN parameter (contribution to the
continuum at 510nm of the AGN continuum emission)
54- 58 F5.2 --- k [3/87] Maximum value of kRMS=RMSk/RMSMk in the
SDSS gri bands (1)
60- 63 F4.2 --- R(1-2) [0.75/1] Maximum values of Spearman's correlation
coefficient R1,2 (2)
65- 67 A3 --- Class Classification: agn, hii=HII galaxy, or
non=non-classified object
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Note (1): where RMSk and RMSMk mean the RMS magnitude deviation for the kth
object in the given SDSS band and the calculated RMS photometry magnitude
deviation calculated by the RMS function, given the mean photometry magnitude
in the given band of the object.
The larger variabilities (RMSk/RMSMk) of the candidates than those of a large
part of QSOs provide further evidence for the true variabilities of the
candidates.
Note (2): Pearson's correlation coefficient between two different band light
curves, an expected feature of truly variable objects.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Nov-2014