Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei

We estimate the dust torus cooling timescale once the active galactic nucleus (AGN) is quenched. In a clumpy torus system, once the incoming photons are suppressed, the cooling timescale of one clump from Tdust = 1000 K to several 10 K is less than 10 years, indicating that the dust torus cooling ti...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 844; no. 1; pp. 21 - 27
Main Authors Ichikawa, Kohei, Tazaki, Ryo
Format Journal Article
LanguageEnglish
Published Philadelphia The American Astronomical Society 20.07.2017
IOP Publishing
Subjects
Active galactic nuclei
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Cooling
COOLING TIME
COSMIC DUST
Dust
DYES
EMISSION
Emission lines
GALAXIES
galaxies: active
galaxies: nuclei
GALAXY NUCLEI
infrared: galaxies
LUMINOSITY
PHOTONS
QUENCHING
Time
Toruses
Tracing
VISIBLE RADIATION
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Summary:We estimate the dust torus cooling timescale once the active galactic nucleus (AGN) is quenched. In a clumpy torus system, once the incoming photons are suppressed, the cooling timescale of one clump from Tdust = 1000 K to several 10 K is less than 10 years, indicating that the dust torus cooling time is mainly governed by the light crossing time of the torus from the central engine. After considering the light crossing time of the torus, the AGN torus emission at 12 m becomes over two orders of magnitude fainter within 100 years after the quenching. We also propose that those "dying" AGNs could be found using the AGN indicators with a different physical scale R such as 12 m band luminosity tracing AGN torus (R ∼ 10 pc) and the optical [O iii]λ5007 emission line tracing narrow line regions (R = 102-4 pc).
Bibliography:Galaxies and Cosmology
AAS01502
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa7891