Dust Reverberation of 3C 273: Torus Structure and Lag-Luminosity Relation

We monitored the z = 0.158 quasar 3C 273 between 2015 and 2019 in the optical (BVrz) and near-infrared (JHK) with the aim to perform dust reverberation mapping. Accounting for host galaxy and accretion disk contributions, we obtained pure dust light curves in JHK. Cross correlations between the V ba...

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Bibliographic Details
Published in:The Astronomical journal 2020-06, Vol.159 (6), p.259
Main Authors: Figaredo, Catalina Sobrino, Haas, Martin, Ramolla, Michael, Chini, Rolf, Blex, Julia, Hodapp, Klaus Werner, Murphy, Miguel, Kollatschny, Wolfram, Chelouche, Doron, Kaspi, Shai
Format: Article
Language:English
Subjects:
ACCRETION DISKS
Active galactic nuclei
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ASYMMETRY
Correlation
CORRELATIONS
COSMIC DUST
Dust
Dust emission
EMISSION
GALAXIES
GALAXY NUCLEI
INCLINATION
Light curve
LUMINOSITY
Mapping
Photometry
QUASARS
Response time
Reverberation
Reverberation mapping
Toruses
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Summary:We monitored the z = 0.158 quasar 3C 273 between 2015 and 2019 in the optical (BVrz) and near-infrared (JHK) with the aim to perform dust reverberation mapping. Accounting for host galaxy and accretion disk contributions, we obtained pure dust light curves in JHK. Cross correlations between the V band and the dust light curves yield an average rest-frame delay for the hot dust of τcent ∼ 410 days. This is a factor of two shorter than that expected from the the dust ring radius Rx ∼ 900 lt-day reported from interferometric studies. The dust covering factor (CF) is about 8%, much smaller than that predicted from the half covering angle of 45° found for active galactic nuclei (AGNs). We analyze the asymmetric shape of the correlation functions and explore whether an inclined biconical bowl-shaped dust torus geometry could bring these findings (τcent, Rx and CF) into a consistent picture. The hot varying dust emission originates from the edge of the bowl rim with a small covering angle 40° < θ < 45°, and we see only the near side of the biconus. Such a dust gloriole with Rx = 900 200 lt-day and an inclination 12° matches the data remarkably well. Comparing the results of 3C 273 with literature for less luminous AGN, we find a lag-luminosity relation τ ∝ L with = 0.33-0.40, flatter than the widely adopted relation with ∼ 0.5. We address several explanations for the new lag-luminosity relation.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/ab89b1