Mid-IR variability and dust reverberation mapping of low-z quasars
Abstract
The continuous operation of the Wide-field Infrared Survey Explorer (WISE) and several ground-based optical transient surveys (CRTS, ASAS-SN and PTF) offer an unprecedented opportunity to systematically explore the dust structures in luminous AGNs. In this poster, I will present the results from a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at z < 0.5 based on these public datasets. We find over 70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time lags in the WISE W1 (~3.4 microns) and W2 (~4.5 microns) bands that are proportional to the square root of the AGN luminosity. In addition, we also characterize how the AGN IR variation signatures change from the near-IR to the 24~microns with the aid of multi-epoch observations from Spitzer and literature K-band RM study. Combining all these IR dust reverberation analysis, we derive the wavelength-dependent torus dust emission size ratios (RK : RW1 : RW2 = 0.6 : 1 : 1.2) and suggest a concentration of the hottest dust grains in the torus innermost regions. Our results support several features of the AGN unification model and provide important constraints on the quasar torus properties.
- Publication:
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American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23530517L