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

Tazaki, Ryo; Ichikawa, Kohei; Kokubo, Mitsuru

doi:10.3847/1538-4357/ab7822

Cited by 25 publications

(17 citation statements)

References 50 publications

(81 reference statements)

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“…The evaporation is indeed fast, of order of 1 day (see BL18). Although the temperature of 1500 [K] is sort of mean value for all grain sizes and species, the assumption of a single temperature is much less justified (BL18, Tazaki et al 2020;Temple et al 2020), and has to be treated as a first approximation. However, in our dynamical model computations of the selective evaporation would be too time consuming, while it could have been done in BL18 model.…”

Section: Dust Temperaturementioning

confidence: 99%

The picture of BLR in 2.5-D FRADO: Dynamics & Geometry

Naddaf,

Czerny,

Szczerba

2021

Preprint

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The dynamics of the Broad Line Region (BLR) in Active galaxies is an open question, direct observational constraints suggests a predominantly Keplerian motion, with possible traces of inflow or outflow. In this paper we study in detail the physically motivated BLR model of Czerny & Hryniewicz (2011) based on the radiation pressure acting on dust at the surface layers of accretion disk (AD). We consider here the realistic prescription of radiation coming from the entire AD acting on a dusty cloud. We use here the realistic description of the dust opacity, and we introduce two simple geometrical models of the local shielding of the dusty cloud. We show that the radiation pressure acting on dusty clouds is strong enough to lead to dynamical outflow from the AD surface, so the BLR has a dynamical character of (mostly failed) outflow. The dynamics strongly depend on the Eddington ratio of the source. Large Eddington ratio sources show a complex velocity field and large vertical velocities with respect to the AD surface, while for lower Eddington ratio sources vertical velocities are small and most of the emission originates close to the AD surface. Cloud dynamics thus determines the 3-D geometry of the BLR.

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Section: Dust Temperaturementioning

confidence: 99%

The picture of BLR in 2.5-D FRADO: Dynamics & Geometry

Naddaf,

Czerny,

Szczerba

2021

Preprint

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“…Thus, in this paper, we solve J pe − J e + J sec,gas + J ion = 0 to find Z d . Solutions of Equation ( 17) are presented in the companion paper (Tazaki et al 2020) (see also Weingartner et al (2006)).…”

Section: Grain Chargingmentioning

confidence: 99%

“…Since dust grains exposed to the radiation from central engine usually become charged with a few hundreds of volts (Weingartner et al 2006;Tazaki et al 2020), thermal sputtering is not likely to occur unless the gas temperature is extremely high.…”

Section: Sputteringmentioning

confidence: 99%

“…In order to suppress silicate feature, submicron-sized grains should be removed. Coulomb explosion could eliminate very small grains ( 0.1 µm) (Weingartner et al 2006;Tazaki et al 2020); however, it is insufficient to destroy sub-micron-sized grains ( 0.1 µm) at the pc-scale regions. Hence, it is not evident how large grains are preferentially supplied to the polar region, while sub-micron-sized grains are removed.…”

Section: Introductionmentioning

confidence: 99%

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Dust Destruction by Drift-induced Sputtering in Active Galactic Nuclei

Tazaki

Ichikawa

2020

ApJ

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Recent mid-infrared high spatial resolution observations have revealed that active galactic nuclei (AGNs) may host a polar dust region with the size of several pc, and such dust may be carried by radiation from the central engine. The polar dust emission often exhibits very weak or absence of the silicate 10-µm emission feature. A possible explanation is that the polar dust is dominated by micronsized large grains because these grains do not show the silicate feature, while it remains unclear how large grains are preferentially supplied to the polar region. We here propose a new scenario describing the prevalence of large grains at the polar region. We show that grains are accelerated to the hypersonic drift velocity by the radiation pressure from AGN, and the hypersonic drift results in dust destruction via kinetic sputtering. Sputtering destroys small grains faster than the large ones, and thus larger grains will be preferentially blown over longer distance. Although the hypersonic drift, or kinetic sputtering, tends to be suppressed for very small grains due to the Coulomb drag, they might also be disrupted by Coulomb explosion. Removal of small grains and/or survival of large grains may explain the lack of a silicate 10-µm emission feature in polar dust emission.

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“…Finally, in extreme environments illuminated by gamma-ray bursts or active galactic nuclei, high energy photons could increase grain charges to excessive values and induce Coulomb explosions (e.g. Waxman & Draine 2000;Tazaki et al 2020).…”

mentioning

confidence: 99%

Radiative transfer of ionizing radiation through gas and dust: the stellar source case

Glatzle

Ciardi

Graziani

2018

Monthly Notices of the Royal Astronomical Society

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We present a new dust extension to the Monte Carlo radiative transfer code crash, which enables it to simulate the propagation of ionizing radiation through mixtures of gas and dust. The new code is applied to study the impact of dust absorption on idealized galactic H ii regions and on small scale reionization. We find that H ii regions are reduced in size by the presence of dust, while their inner temperature and ionization structure remain largely unaffected. In the small scale reionization simulation, dust hardens ionization fronts and delays the overlap of ionized bubbles. This effect is found to depend only weakly on the assumed abundance of dust in underdense regions.

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

Cited by 25 publications

References 50 publications

The picture of BLR in 2.5-D FRADO: Dynamics & Geometry

The picture of BLR in 2.5-D FRADO: Dynamics & Geometry

Dust Destruction by Drift-induced Sputtering in Active Galactic Nuclei

Radiative transfer of ionizing radiation through gas and dust: the stellar source case

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