X-ray signatures of the polar dusty gas in AGN

Abstract

Recent mid-infrared interferometry observations of nearby active galactic nuclei (AGN) revealed that a significant part of the dust emission extends in the polar direction, rather than the equatorial torus/disk direction as expected by the traditional unification model. We study the X-ray signatures of this polar dusty gas with ray-tracing simulations. Different from those from the ionized gas, the scattered emission from the polar dusty gas produces self-absorption and neutral-like fluorescence lines, which are potentially a unique probe of the kinematics of the polar dusty gas. The anomalously small Fe Ka/Si Ka ratios of type II AGN observed previously can be naturally explained by the polar dusty gas, because the polar emission does not suffer from heavy absorption by the dense equatorial gas. The observed Si Ka lines of the Circinus galaxy and NGC 1068 show blue-shifts with respect to the systemic velocities of the host galaxies, consistent with an outflowing scenario of the Si Ka-emitting gas. The 2.5-3 keV image of the Circinus galaxy is elongated along the polar direction, consistent with an origin of the polar gas. These results show that the polar-gas-scattered X-ray emission of type II AGN is an ideal objective for future X-ray missions, such as Athena.

10 pages, 8 figs, to appear on MNRAS

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Cited by in corpus (10)

• Systematic Study of AGN Clumpy Tori with Broadband X-ray Spectroscopy: Updated Unified Picture of AGN Structure
• The dust-gas AGN torus as constrained from X-ray and mid-infrared observations
• Hard X-Ray to Radio Multiwavelength SED Analysis of Local U/LIRGs in GOALS Sample with Self-consistent AGN Model Including Polar-dust Component
• Application of X-Ray Clumpy Torus Model (XCLUMPY) to 10 Obscured Active Galactic Nuclei Observed with Suzaku and NuSTAR
• X-ray Constraint on Location of AGN Torus in Circinus Galaxy
• Ray-tracing simulations and spectral models of X-ray radiation in dusty media
• A multiwavelength-motivated X-ray model for the Circinus Galaxy
• The complex infrared dust continuum emission of NGC1068: ground-based N- and Q-band spectroscopy and new radiative transfer models
• X-ray Simulations of Polar Gas in Accreting Supermassive Black Holes
• Ray-tracing simulations of the Soft X-ray Scattered Emission in obscured Active Galactic Nuclei