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Title: Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei

Abstract

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 T {sub dust} = 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 μ 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 μ m band luminosity tracing AGN torus ( R ∼ 10 pc) and the optical [O iii] λ 5007 emission line tracing narrow line regions ( R = 10{sup 2–4} pc).

Authors:
 [1];  [2]
  1. Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)
  2. Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578 (Japan)
Publication Date:
OSTI Identifier:
22663379
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 844; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COOLING TIME; COSMIC DUST; DYES; EMISSION; GALAXIES; GALAXY NUCLEI; LUMINOSITY; PHOTONS; QUENCHING; VISIBLE RADIATION

Citation Formats

Ichikawa, Kohei, and Tazaki, Ryo, E-mail: k.ichikawa@astro.columbia.edu. Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7891.
Ichikawa, Kohei, & Tazaki, Ryo, E-mail: k.ichikawa@astro.columbia.edu. Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei. United States. doi:10.3847/1538-4357/AA7891.
Ichikawa, Kohei, and Tazaki, Ryo, E-mail: k.ichikawa@astro.columbia.edu. Thu . "Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei". United States. doi:10.3847/1538-4357/AA7891.
@article{osti_22663379,
title = {Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei},
author = {Ichikawa, Kohei and Tazaki, Ryo, E-mail: k.ichikawa@astro.columbia.edu},
abstractNote = {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 T {sub dust} = 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 μ 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 μ m band luminosity tracing AGN torus ( R ∼ 10 pc) and the optical [O iii] λ 5007 emission line tracing narrow line regions ( R = 10{sup 2–4} pc).},
doi = {10.3847/1538-4357/AA7891},
journal = {Astrophysical Journal},
number = 1,
volume = 844,
place = {United States},
year = {Thu Jul 20 00:00:00 EDT 2017},
month = {Thu Jul 20 00:00:00 EDT 2017}
}