J/MNRAS/499/6053 Indiv. opt. variability of AGNs from MEXSAS2 (Laurenti+, 2020)
Individual optical variability of Active Galactic Nuclei from the
MEXSAS2 sample.
Laurenti M., Vagnetti F., Middei R., Paolillo M.
<Mon. Not. R. Astron. Soc. 499, 6053 (2020)>
=2020MNRAS.499.6053L 2020MNRAS.499.6053L (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Active gal. nuclei ; QSOs
Keywords: surveys - galaxies: active - quasars: general
Abstract:
At present, most of the variability studies of active galactic nuclei
(AGNs) are based on ensemble analyses. Nevertheless, it is interesting
to provide estimates of the individual variability properties of each
AGN, in order to relate them with intrinsic physical quantities. A
useful dataset is provided by the Catalina Surveys Data Release 2
(CSDR2), which encompasses almost a decade of photometric measurements
of ∼500 million objects repeatedly observed hundreds of times.We aim
to investigate the individual optical variability properties of 795
AGNs originally included in the Multi-Epoch XMMSerendipitous AGN
Sample 2 (MEXSAS2). Our goals consist in: (i) searching for
correlations between variability and AGN physical quantities; (ii)
extending our knowledge of the variability features of MEXSAS2 from
the X-ray to the optical.We use the structure function (SF) to analyse
AGN flux variations. We model the SF as a power-law,
SF(tau)=A(tau/tau_0)gamma, and we compute its variability parameters.
We introduce the V-correction as a simple tool to correctly quantify
the amount of variability in the rest frame of each source.We find a
significant decrease of variability amplitude with increasing
bolometric, optical and X-ray luminosity. We obtain the indication of
an intrinsically weak positive correlation between variability
amplitude and redshift, z. Variability amplitude also appears to be
positively correlated with alpha_{ox}.The slope of the power-law SF,
gamma, is weakly correlated with the bolometric luminosity L_{bol}
and/or with the black hole mass M_{BH}. When comparing optical to
X-ray variability properties, we find that X-ray variability amplitude
is approximately the same for those AGNs with larger or smaller
variability amplitude in the optical.On the contrary, AGNs with
steeper SF in the optical do present steeper SF in the X-ray, and vice
versa.
Description:
We present the reference sample of our individual optical variability
analysis from a crossmatch between the the Catalina Surveys Data
Release 2 (CSDR2) and the MEXSAS2 catalogue (Serafinelli et al. ,
2017FrASS...4...21S 2017FrASS...4...21S), an updated version of the Multi-Epoch X-ray
Serendipitous AGN Sample (MEXSAS, Vagnetti et al 2016A&A...593A..55V 2016A&A...593A..55V,
Cat. J/A+A/593/A55).
The variability parameters derived from the SF analysis are
complemented with physical quantities, such as the bolometric
luminosity, black hole mass and Eddington ratio from Shen et al.
(2011ApJS..194...45S 2011ApJS..194...45S, Cat. J/ApJS/194/45) and Kozlowski
(2017ApJS..228....9K 2017ApJS..228....9K, Cat. J/ApJS/228/9), as well as the redshift, the
X-ray luminosity in the 0.5-4.5 keV band, the average magnitude in the
V band, the V-band luminosity. The reference sample contains data for
795 AGNs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sample.dat 304 795 The reference sample
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See also:
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/A+A/593/A55 : MEXSAS catalogue (Vagnetti+, 2016)
J/ApJS/228/9 : Physical parameters of ∼300000 SDSS-DR12 QSOs (Kozlowski, 2017)
Byte-by-byte Description of file: sample.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- MEXSAS2 Source number in the MEXSAS2 catalogue
6- 23 A18 --- SDSS SDSS source name (HHMMSS.ss+DDMMSS.s)
25- 44 F20.16 deg RAdeg Right ascension of
SDSS identification (J2000)
46- 68 F23.19 deg DEdeg Declination of SDSS identification (J2000)
70- 82 F13.10 --- logA Uncorrected SF variability amplitude
84-104 F21.18 --- logAVcorr V-corrected SF variability amplitude
106-119 F14.12 --- e_logA Error on logA_Vcorr
121-135 E15.10 --- gamma Slope of the power-law SF
137-150 F14.12 --- e_gamma Error on gamma
152-173 E22.17 --- Rsquared Coefficient of determination
175-193 F19.17 --- z Redshift
195-213 F19.16 [Msun] log(Mbh) Logarithm of black hole mass
215-232 F18.15 [10-7W/Hz] log(Lbol) Logarithm of bolometric luminosity
234-254 F21.18 [-] log(Edd) Logarithm of Eddington ratio
256-266 F11.8 mag Vmag Average magnitude in Johnson's V band
268-285 F18.15 [10-7W/Hz] log(LV) Logarithm of V-band luminosity
287-297 F11.8 [10-7W/Hz] log(LX) Log X-ray luminosity, 0.5-4.5 keV band
299-301 I3 --- Nepo Number of optical observations
303-304 I2 --- Nepx Number of X-ray observations
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Acknowledgements:
Marco Laurenti, marco.laurenti(at)roma2.infn.it,
Universita di Roma "Tor Vergata"
(End) M. Laurenti [Tor Vergata Roma Univ.], P. Vannier [CDS] 19-Oct-2020