J/ApJ/894/24 Optical variability of AGN from the HSC SSP survey (Kimura+, 2020)
Properties of AGN multiband optical variability in the HSC SSP transient survey.
Kimura Y., Yamada T., Kokubo M., Yasuda N., Morokuma T., Nagao T.,
Matsuoka Y.
<Astrophys. J., 894, 24 (2020)>
=2020ApJ...894...24K 2020ApJ...894...24K
ADC_Keywords: Active gal. nuclei; Photometry, ugriz; Redshifts; Surveys
Keywords: Active galactic nuclei ; Low-luminosity active galactic nuclei ;
AGN host galaxies ; Active galaxies ; Supermassive black holes ;
Optical observation
Abstract:
We study variability of active galactic nuclei (AGNs) by using the
deep optical multiband photometry data obtained from the Hyper
Suprime-Cam Subaru Strategic Program (HSC SSP) survey in the COSMOS
field. The images analyzed here were taken with 8, 10, 13, and 15
epochs over three years in the g, r, i, and z bands, respectively. We
identified 491 robust variable AGN candidates, down to i=25mag and
with redshift up to 4.26. Ninety percent of the variability-selected
AGNs are individually identified with the X-ray sources detected in
the Chandra COSMOS Legacy survey. We investigate their properties in
variability by using structure function analysis and find that the
structure function for low-luminosity AGNs (Lbol≲1045erg/s) shows
a positive correlation with luminosity, which is the opposite trend
for the luminous quasars. This trend is likely to be caused by a
larger contribution of the host galaxy light for lower-luminosity
AGNs. Using the model templates of galaxy spectra, we evaluate the
amount of host galaxy contribution to the structure function analysis
and find that dominance of the young stellar population is needed to
explain the observed luminosity dependence. This suggests that
low-luminosity AGNs at 0.8≲z≲1.8 are predominantly hosted in
star-forming galaxies. The X-ray stacking analysis reveals the
significant emission from the individually X-ray undetected AGNs in
our variability-selected sample. The stacked samples show very large
hardness ratios in their stacked X-ray spectrum, which suggests that
these optically variable sources have large soft X-ray absorption by
dust-free gas.
Description:
Hyper Suprime-Cam Subaru Strategic Program (HSC SSP;
e.g. Aihara+ 2018PASJ...70S...8A 2018PASJ...70S...8A) time-domain observations were
conducted as a part of the UltraDeep layer from 2014 May to 2017 April
with five broadband filters (g, r, i, z, y) in the COSMOS field. The
observations were carried with fair cadence with more than eight
epochs for each band. We did not use the y-band data since the y-band
data has a relatively shallow depth. See Section 2.1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 54 491 Catalog of the variable AGNs
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See also:
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/ApJS/154/519 : Properties of ultraluminous X-ray candidates (Swartz+, 2004)
J/A+A/451/457 : X-ray properties of AGN in CDFS (Tozzi+, 2006)
J/ApJ/665/990 : SDSS DR2 BAL QSOs (Ganguly+, 2007)
J/AJ/133/186 : Opt. spectroscopy of 77 luminous AGNs and QSOs (Lacy+, 2007)
J/ApJ/663/81 : SED of hard X-ray selected AGN in XMDS (Polletta+, 2007)
J/A+A/467/73 : 3σ hard sample of XMDS survey (Tajer+, 2007)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/ApJ/742/61 : Phot. redshift of AGNs from XMM- & C-COSMOS (Salvato+ 2011)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/MNRAS/416/1844 : 2XMM ultraluminous X-ray source candidates (Walton+, 2011)
J/A+A/559/A14 : VIMOS VLT Deep Survey final data release (Le Fevre+, 2013)
J/ApJ/805/122 : X-ray properties of PHL1811 analogs and WLQs (Luo+, 2015)
J/ApJS/220/12 : FMOS-COSMOS survey III. 0.7<z<2.5 gal. (Silverman+, 2015)
J/A+A/584/A106 : Catalogues of variable AGNs (Simm+, 2015)
J/ApJ/819/62 : The COSMOS-Legacy Survey (CLS) catalog (Civano+, 2016)
J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
J/ApJ/825/7 : Evolution of ∼6Ms CDF-S galaxies (Lehmer+, 2016)
J/ApJ/817/34 : C-COSMOS Legacy multiwavelength catalog (Marchesi+, 2016)
J/ApJS/225/27 : 3D-HST Survey: grism spectra master cat. (Momcheva+, 2016)
J/ApJS/228/9 : Physical param. of ∼300000 SDSS-DR12 QSOs (Kozlowski, 2017)
J/ApJS/233/17 : Swift/BAT AGN spectroscopic survey. V. X-ray (Ricci+, 2017)
J/ApJ/858/77 : DEIMOS 10K sp. survey in COSMOS field (Hasinger+, 2018)
J/A+A/627/A33 : Optically variable AGN in COSMOS field (De Cicco+, 2019)
J/ApJ/870/31 : BAT AGN spectroscopic survey. XI. IR phot. (Ichikawa+, 2019)
http://hsc-release.mtk.nao.ac.jp/doc/index.php/database/ : HSC SSP database
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 -- Seq [1/491] Identification number of variable AGN
5- 13 F9.5 deg RAdeg [149.5/150.9] Right Ascension (J2000)
15- 21 F7.5 deg DEdeg [1.6/2.8] Declination (J2000)
23- 27 F5.2 mag imag [17.56/25.87] i band cmodel AB magnitude
29 I1 -- Xfl [0/1] X ray detection flag (1=detected)
31 I1 -- gfl [0/1] g band 'variability' flag (1=variable)
33 I1 -- rfl [0/1] r band 'variability' flag (1=variable)
35 I1 -- ifl [0/1] i band 'variability' flag (1=variable)
37 I1 -- zfl [0/1] z band 'variability' flag (1=variable)
39 I1 -- Ncorr [1/6] Number of 'correlation'-flagged band-pairs
41- 45 F5.3 -- z [0.04/4.26] Spectroscopic or photometric redshift
47 I1 -- r_z [1/4] Redshift reference (1)
49- 54 I6 -- COSMOS2015 [263032/979571] Identification number listed
in COSMOS2015 (Laigle+, 2016, J/ApJS/224/24)
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Note (1): Reference redshift as follows:
1 = Spectroscopic redshift from the HSC SSP UltraDeep Survey multiband
stacked catalog (316 occurrences)
2 = Spectroscopic redshift from DEIMOS cat. (Hasinger+, 2018, J/ApJ/858/77 ;
21 occurrences)
3 = Photometric redshift from 'zbest' listed in the Chandra catalog
(Marchesi+ 2016, J/ApJ/817/34 ; 123 occurrences)
4 = Photometric redshift from 'ZPDF' listed in the COSMOS2015 catalog
(Laigle+ 2016, J/ApJS/224/24 ; 31 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Sep-2021