J/ApJ/886/33 MIR reverberation mapping analysis of 87 z<0.5 PG AGNs (Lyu+, 2019)
Mid-IR variability and dust reverberation mapping of low-z quasars.
I. Data, methods, and basic results.
Lyu J., Rieke G.H., Smith P.S.
<Astrophys. J., 886, 33 (2019)>
=2019ApJ...886...33L 2019ApJ...886...33L
ADC_Keywords: Active gal. nuclei; Photometry, infrared; Redshifts; Surveys
Keywords: Active galactic nuclei ; Quasars ; Radio loud quasars ;
Radio quiet quasars ; Infrared astronomy ; Reverberation mapping ;
Time series analysis ; Dust continuum emission ;
Extragalactic astronomy ; Supermassive black holes ; Infrared galaxies
Abstract:
The continued operation of the Wide-field Infrared Survey Explorer
(WISE), combined with several ground-based optical transient surveys
(e.g., CRTS, ASAS-SN, and PTF), offers an unprecedented opportunity to
explore the dust structures in luminous active galactic nuclei (AGNs).
We use these data for a mid-IR dust reverberation mapping (RM) study
of 87 archetypal Palomar-Green quasars at z≲0.5. To cope with various
contaminations of the photometry data and the sparse time sampling of
the light curves, procedures to combine these data sets and retrieve
the dust RM signals have been developed. We find that ∼70% of the
sample (with a completeness correction up to 95%) has convincing
mid-IR time lags in the WISE W1 (∼3.4µm) and W2 (∼4.5µm) bands,
and they are proportional to the square root of the AGN luminosity.
Combined with previous K-band (∼2.2µm) RM results in the
literature, the inferred dust emission size ratios are
RK:RW1:RW2=0.6:1:1.2. Under simple assumptions, we put
preliminary constraints on the projected dust surface density at these
bands and reveal the possibly different torus structures among
hot-dust-deficient, warm-dust-deficient, and normal quasars from the
reverberation signals. With multi-epoch Spitzer data and later WISE
photometry, we also explore AGN IR variability at 10-24µm over a
5yr timescale. Except for blazars and flat-spectrum radio sources, the
majority of AGNs have typical variation amplitudes at 24µm of no
more than 10% of that in the W1 band, indicating that the dust
reverberation signals damp out quickly at longer wavelengths. In
particular, steep-spectrum radio quasars also lack strong 24µm
variability, consistent with the unification picture of radio-loud
AGNs.
Description:
We collected optical photometry of the Palomar-Green (PG) quasars from
the Catalina Real-Time Transient Survey (CRTS;
Drake+ 2009, J/ApJ/696/870). This program utilizes two Steward
Observatory telescopes, a 1.5m telescope on Mt. Lemmon, Arizona, and a
0.68m telescope on Mt. Bigelow, Arizona. Both survey the northern sky,
covering timescales from minutes to years. We gathered the 2005-2013
photometry values from the public archive of the second data release.
We also utilized the V-band optical data from the All-Sky Automated
Survey for Supernovae (ASAS-SN; Shappee+, 2014, J/ApJ/788/48), which
are publicly available at the ASAS-SN light-curve servers
(Kochanek+ 2017PASP..129j4502K 2017PASP..129j4502K). The data were obtained through a
global network of 20 14cm diameter telescopes (camera lenses) with
commercial-level CCD cameras that have observed nearly the entire sky
continuously since 2012.
Finally, we gathered the optical time-sequence photometry for the PG
quasars from the Palomar Transient Factory (PTF; Law+ 2009PASP..121.1395L 2009PASP..121.1395L)
Data Release 3 (DR3), which includes all data collected during the
survey from 2009 March to 2012 December and some selected data
obtained from 2013 to 2015 January. This survey was done with the
Palomar 48 inch (1.2m) Samuel Oschin Telescope with a typical 2.0"
FWHM imaging resolution.
We gathered all of the single-epoch profile-fit photometry
measurements in the W1 (∼3.4um) and W2 (∼4.6um) bands from the WISE
and NEOWISE missions, up to the NEOWISE 2019 Data Release, from the
NASA/IPAC Infrared Science Archive. Typically, these data cover a time
period from 2010 January to 2018 December with a 3yr gap between 2011
and 2014. Each object was observed for 12-13 epochs, with 10-20 exposures
acquired within each epoch.
To test for variability at λ>20um, we obtained MIPS 24um
measurements (PID 40053 and PID 50099; PI: George Rieke) of a
heterogeneous sample of quasars that had been measured at the same
wavelength by Spitzer for various previous observing programs. All of
the observations were conducted during the Spitzer cryogenic mission
from 2004 to 2009 and sample a time interval of 3-4yr.
To extend the time sampling to 2010, we collected WISE W4 measurements
at 22um for 136 of these objects from the ALLWISE Source Catalog.
Low-resolution (R∼60-130) mid-IR spectroscopic observations of all 87
PG quasars were obtained using the Spitzer IRS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 108 469 Quasar flux measurements at 24 microns and
the variability results for 139 sources
table4.dat 105 87 Summary of the mid-IR reverberation properties
table5.dat 93 174 PG quasar variability at 12 and 22 microns
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See also:
VIII/82 : 2nd Epoch Molonglo Galactic Plane Survey (MGPS-2) (Murphy+, 2007)
II/328 : AllWISE Data Release (Cutri+ 2013)
J/ApJ/269/352 : Quasar evolution (Schmidt+, 1983)
J/ApJS/95/1 : Atlas of Quasar Energy Distributions (Elvis+ 1994)
J/ApJ/613/682 : AGN central masses & broad-line region sizes (Peterson+, 2004)
J/ApJ/640/579 : Near-infrared spectra of 27 SDSS quasars (Glikman+, 2006)
J/PASP/119/994 : MIPS 24um calibrators (Engelbracht+, 2007)
J/ApJ/666/806 : SED of Spitzer quasars (QUEST) (Netzer+, 2007)
J/AJ/136/2373 : Type 2 quasars from SDSS (Reyes+, 2008)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/AJ/142/3 : 1.4GHz observations of Stripe 82 (Hodge+, 2011)
J/ApJ/788/159 : 17 Seyfert 1 galaxies light curves (Koshida+, 2014)
J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
J/A+A/561/L8 : BRJK photometry of Seyfert galaxy WPVS48 (Pozo Nunez+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/214/23 : IR spectra and photometry of z<0.5 quasars (Shi+, 2014)
J/ApJS/216/17 : AKARI 2.5-5um spectra of nearby Type-1 AGNs (Kim+, 2015)
J/AJ/149/11 : Spectra of candidate standard stars in mid-IR (Sloan+, 2015)
J/ApJ/801/127 : 3.6um, 4.5um, B & V light curves of NGC 6418 (Vazquez+, 2015)
J/ApJ/831/168 : 6GHz JVLA obs. of low-z SDSS quasars (Kellermann+, 2016)
J/ApJS/224/26 : SEDs of Roma BZCAT blazars (Mao+, 2016)
J/ApJ/836/186 : Continuum-band lags in SDSS QSOs from PS1 obs. (Jiang+, 2017)
J/ApJ/841/76 : Intrinsic far-IR SED of luminous AGNs (Lyu+, 2017)
J/MNRAS/471/59 : Intrinsic AGN SEDs in PG quasars (Lani+, 2017)
J/A+A/620/A137 : CCD B,V,R,I,Ha photometry of 3C120 (Ramolla+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Quasar identifier
26- 31 F6.3 --- z [0.003/0.5]? Redshift
33- 38 F6.1 d JD [3058.1/5409] Julian Date; JD-2450000
40 A1 --- f_JD [a] Flag on JD (1)
42- 47 F6.1 mJy F24 [1.1/2882.8]? The 24 micron flux density
49- 52 F4.1 mJy e_F24 [0.2/65.3]? Uncertainty in F24
54- 57 F4.1 --- StDev [0/71.1]? Standard deviation of flux density change
59-107 A49 --- Comm Comments
108 A1 --- Flag [bcdef] Flag (1)
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Note (1): Flag as follows:
a = For midpoint of the WISE observations.
b = The strong 18 micron feature in the spectrum of this source
(Shi+ 2014, J/ApJS/214/23) combined with the ∼1um bluer bandpass of
the W4 filter compared with the MIPS one can account for the
higher signal seen by WISE.
c = Steep-spectrum radio quasar (SSRQ) indicates that the spectral index
between 1.4 and 5GHz is ≤-0.7. Radio data obtained from summary in
NASA Extragalactic Database (NED) and other sources. (see Section 4.4
for details.)
d = Blazars are identified from Mao (2016, J/ApJS/224/26) and
additional sources, see text.
e = Flat-spectrum radio quasar (FSRQ) indicates that the spectral index
between 1.4 and 5GHz is >-0.7.
f = This source is radio-intermediate by our criteria, but radio-loud using
others (Laor+ 2019MNRAS.482.5513L 2019MNRAS.482.5513L); given its flat spectrum
also, we classify it as radio-loud.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Quasar identifier
13- 16 F4.2 --- z [0.03/0.47] Redshift
18- 21 A4 --- SED IR SED type from Lyu+ 2017ApJ...835..257L 2017ApJ...835..257L
23- 26 F4.1 Lsun Lbol [10.6/13.4] AGN bolometric luminosity (1)
28- 32 F5.2 [mag] loge-s [-2.88/1.09] DRW model amplitude
(loge(σ)) (2)
34- 37 F4.2 [mag] loge-t [2.66/7.74] DRW model timescale
(loge(τ)) (2)
39- 44 F6.1 --- delt [79.6/2607.5] IR dust time-lag (observed frame)
from WISE W1-band light curves
(ΔtW1,χ2) (3)
46- 50 F5.1 --- e_delt [0.4/744.1] delt uncertainty
52- 55 F4.1 --- AmpW1 [0/20] IR-optical variability amplitude factor
from WISE W1-band light curves
57- 59 F3.1 --- e_AmpW1 [0/1] AmpW1 uncertainty
61- 64 I4 --- deltW1c [-300/3700] W1-band dust time-lag suggested
by cross-correlation analysis
(ΔtW1,CCF)
66- 69 F4.2 --- CCFW1 [0.3/0.99] Peak CCF value for W1
71- 76 F6.1 --- deltW2 [83.8/2614.9] IR dust time-lag (observed frame)
from WISE W2-band light curves
(ΔtW2,χ2)
78- 82 F5.1 --- e_deltW2 [0.2/815.7] deltW2 uncertainty
84- 87 F4.1 --- AmpW2 [0/17.3] IR-optical variability amplitude
factor from WISE W2-band light curves
89- 91 F3.1 --- e_AmpW2 [0/1.3] AmpW2 uncertainty
93- 96 I4 --- deltW2c [29/3700] W2-band dust time-lag suggested
by cross-correlation analysis
(ΔtW2,CCF)
98- 101 F4.2 --- CCFW2 [0.31/0.98] Peak CCF value for W2
103 I1 --- f_W1 [0/1] Flag on W1 data
(1=used for reverberation analysis)
105 I1 --- f_W2 [0/1] Flag on W2 data
(1=used for reverberation analysis)
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Note (1): AGN bolometric luminosity estimated from IR SED decompositions
(Lyu+ 2017ApJ...835..257L 2017ApJ...835..257L) with bolometric corrections described
in Section 4.2.1.
Note (2): DRW model amplitude (σ) and timescale (τ) from fitting
the combined V-band light curve with the JAVELIN code, both in natural logs.
Note (3): IR dust time-lag (observed frame) from fitting the WISE W1-band
light curves with our model. We have made necessary corrections as
stated in Section 3.3. This column presents the finally adopted values
of the time lags (in the observed frame) that is used in our analysis;
see Section 4.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Quasar identifier (1)
14- 20 F7.1 d MJD-12 [52989.7/55387.5] Modified Julian Date
of 12 micron observation
22- 27 F6.2 mJy F12 [10/478.2]? WISE (W3) 12um flux density
29- 34 F6.3 mJy e_F12 [0.27/15]? Uncertainty in F12
36- 41 F6.3 --- StDev-12 [-4.8/6.4]? Standard deviation of 12um flux
density change
43- 46 F4.2 mag DelM-W3 [0/0.3]? WISE W3 band magnitude change
48- 54 F7.1 d MJD-22 [52989.7/55387.5]? Modified Julian Date
of 22 micron observation
56- 61 F6.2 mJy F22 [12/893]? WISE (W4) 22um flux density
63- 67 F5.2 mJy e_F22 [0.7/19.1]? Uncertainty in F22
69- 73 F5.2 --- StDev-22 [-2.6/10.3]? Standard deviation of 22um flux
density change
75- 78 F4.2 mag DelM-W4 [0/0.4]? WISE W4 band magnitude change
80- 93 A14 --- Comm Comment
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Note (1): PG 1626+544 is very likely a misprint for PG 1626+554;
corrected at CDS.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Apr-2021