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Mid-IR Variability and Dust Reverberation Mapping of Low-$z$ Quasars. I. Data, Methods and Basic Results
Astrophysics of Galaxies · Submitted 24 Sep 2019
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We find $\sim$70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time-lags in the WISE W1 ($\sim3.4~\mu m$) and W2 ($\sim4.5~\mu m$) bands and they are proportional to the square root of the AGN luminosity.
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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) offer an unprecedented opportunity to explore the dust structures in luminous AGNs. We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at $z\lesssim0.5$. To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these datasets and retrieve the dust RM signals have been developed. We find $\sim$70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time-lags in the WISE W1 ($\sim3.4~\mu m$) and W2 ($\sim4.5~\mu m$) bands and they are proportional to the square root of the AGN luminosity. Combined with previous K-band ($\sim2.2~\mu m$) RM results in the literature, the inferred dust emission size ratios are $R_{K}:R_{W1}:R_{W2}=0.6:1:1.2$. 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--24 $\mu m$ over a 5-year time-scale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24 $\mu m$ no more than 10% of that in the W1 band, indicating the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24 $\mu m$ variability, consistent with the unification picture of radio-loud AGN.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | 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) offer an unprecedented opportunity to explore the dust structures in luminous AGNs. | background 1.00 | 0.08 | 0.02 | asserted 0.83 |
| s1 | We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at $z\lesssim0.5$. | contribution 0.90 | 0.96 | 0.03 | asserted 0.98 |
| s2 | To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these datasets and retrieve the dust RM signals have been developed. | method 0.99 | 0.82 | 0.02 | asserted 0.99 |
| s3 | We find $\sim$70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time-lags in the WISE W1 ($\sim3.4~\mu m$) and W2 ($\sim4.5~\mu m$) bands and they are proportional to the square root of the AGN luminosity. | result 1.00 | 0.97 | 0.60 | asserted 1.00 |
| s4 | Combined with previous K-band ($\sim2.2~\mu m$) RM results in the literature, the inferred dust emission size ratios are $R_{K}:R_{W1}:R_{W2}=0.6:1:1.2$. | result 0.99 | 0.87 | 0.19 | asserted 1.00 |
| s5 | 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. | interpretation 0.82 | 0.95 | 0.13 | hedged possibility 0.87 |
| s6 | With multi-epoch Spitzer data and later WISE photometry, we also explore AGN IR variability at 10--24 $\mu m$ over a 5-year time-scale. | contribution 0.82 | 0.95 | 0.03 | asserted 0.90 |
| s7 | Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24 $\mu m$ no more than 10% of that in the W1 band, indicating the dust reverberation signals damp out quickly at longer wavelengths. | result 0.97 | 0.90 | 0.13 | hedged possibility 0.61 |
| s8 | In particular, steep-spectrum radio quasars also lack strong 24 $\mu m$ variability, consistent with the unification picture of radio-loud AGN. | interpretation 0.62 | 0.74 | 0.05 | hedged possibility 0.84 |
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Original 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) offer an unprecedented opportunity to explore the dust structures in luminous AGNs. We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at $z\lesssim0.5$. To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these datasets and retrieve the dust RM signals have been developed. We find $\sim$70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time-lags in the WISE W1 ($\sim3.4~\mu m$) and W2 ($\sim4.5~\mu m$) bands and they are proportional to the square root of the AGN luminosity. Combined with previous K-band ($\sim2.2~\mu m$) RM results in the literature, the inferred dust emission size ratios are $R_{K}:R_{W1}:R_{W2}=0.6:1:1.2$. 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--24 $\mu m$ over a 5-year time-scale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24 $\mu m$ no more than 10% of that in the W1 band, indicating the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24 $\mu m$ variability, consistent with the unification picture of radio-loud AGN.
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5 arXiv papers cite this in 18 sentences
Papers citing it · 12 sentences without a confident label
Compares with it 1 paper
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Our MIR lags also agree with the lags measured for tens of PG quasars in [ref] over the same luminosity range, indicating negligible evolution from $z<0.5$ to $z∼1$.
Dust Reverberation Mapping in Distant Quasars from Optical and Mid-Infrared Imaging Surveys · Results · 0.93
Cites it as background 1 paper
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have also been conducted to make a progress in studying the geometry and structure around the central region of the dust torus [ref] , and [ref] very recently presented the results of a systematic dust-reverberation survey at longer wavelengths ($3.4$ and $4.5 μ$m) for the Palomar–Green (PG) quasars [ref] .
Reverberation Measurements of the Inner Radii of the Dust Tori in Quasars · Introduction · 0.86
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