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Emission-Line Probes of Circumnuclear Dust in AGNs

Joseph C. Shields·Richard W. Pogge·Michael M. De Robertis
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Abstract

Emission lines that trace elements subject to strong depletion onto grains provide a means for probing the dust content of AGNs. Examples include infrared [FeII] and optical [CaII] lines. The excitation mechanisms underlying the [FeII] lines remain controversial, resulting in related disagreement over the gas-phase abundance of iron in Seyfert narrow-line regions. In this contribution we emphasize the utility of the [CaII] lines as a consistency test for claims of grain destruction affecting the [FeII] lines. A search for [CaII] emission in NGC 1068 at a location of strongest [FeII] emission along the radio jet yields a strong upper limit, but no detection. This result suggests that grains survive largely intact in a region that otherwise shows strong evidence of shock processing.

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Joseph C. Shields, Richard W. Pogge, Michael M. De Robertis. 1998-09-20. Emission-Line Probes of Circumnuclear Dust in AGNs. https://arxiv.org/abs/astro-ph/9809247

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