Dust Destruction by Charging: A Possible Origin of Gray Extinction Curves of Active Galactic Nuclei

Observed extinction curves of active galactic nuclei (AGNs) are significantly different from those observed in the Milky Way. The observations require preferential removal of small grains at the AGN environment; however, the physics for this remains unclear. In this paper, we propose that dust destr...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 892; no. 2; pp. 84 - 89
Main Authors Tazaki, Ryo, Ichikawa, Kohei, Kokubo, Mitsuru
Format Journal Article
LanguageEnglish
Published Philadelphia The American Astronomical Society 01.04.2020
IOP Publishing
Subjects
Active galactic nuclei
Astrophysical dust processes
Astrophysics
Charged particles
Charging
Destruction
Dust
Explosions
Extinction
Milky Way
Photoelectric emission
Photoelectricity
Radiation
Tensile strength
Tensile stress
Ultraviolet extinction
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Summary:Observed extinction curves of active galactic nuclei (AGNs) are significantly different from those observed in the Milky Way. The observations require preferential removal of small grains at the AGN environment; however, the physics for this remains unclear. In this paper, we propose that dust destruction by charging, or Coulomb explosion, may be responsible for AGN extinction curves. Harsh AGN radiation makes a dust grain highly charged through photoelectric emission, and grain fission via Coulomb explosion occurs when the electrostatic tensile stress of a charge grain exceeds its tensile strength. We show that Coulomb explosion can preferentially remove both small silicate and graphite grains and successfully reproduce both flat extinction curve and the absence of 2175 bump.
Bibliography:Galaxies and Cosmology
AAS22498
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab7822