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Recent mid-infrared interferometry observations of nearby active galacticnuclei (AGN) revealed that a significant part of the dust emission extends inthe polar direction, rather than the equatorial torus/disk direction asexpected by the traditional unification model. We study the X-ray signatures ofthis polar dusty gas with ray-tracing simulations. Different from those fromthe ionized gas, the scattered emission from the polar dusty gas producesself-absorption and neutral-like fluorescence lines, which are potentially aunique probe of the kinematics of the polar dusty gas. The anomalously small FeKa/Si Ka ratios of type II AGN observed previously can be naturally explainedby the polar dusty gas, because the polar emission does not suffer from heavyabsorption by the dense equatorial gas. The observed Si Ka lines of theCircinus galaxy and NGC 1068 show blue-shifts with respect to the systemicvelocities of the host galaxies, consistent with an outflowing scenario of theSi Ka-emitting gas. The 2.5-3 keV image of the Circinus galaxy is elongatedalong the polar direction, consistent with an origin of the polar gas. Theseresults show that the polar-gas-scattered X-ray emission of type II AGN is anideal objective for future X-ray missions, such as Athena.

X-ray signatures of the polar dusty gas in AGN