Implications of Nonequatorial Relativistic Accretion Flows for Ultrafast Inflows in Active Galactic Nuclei

Abstract Motivated by a number of X-ray observations of active galactic nuclei (AGNs) that exhibit a potential signature of ultrafast inflows (UFIs), we consider in this work a scenario that UFIs can be physically identified as weakly magnetized hydrodynamic accretion flows that are guided and channeled by a poloidal magnetic field into low-to-mid-latitude above the equatorial disk. In the context of general relativistic hydrodynamics (GRHD) under a weak-field limit in Kerr spacetime, we present a set of preliminary results by numerically calculating the physical property of GRHD flows (e.g., kinematics and density distribution) in an effort to simulate redshifted absorption line spectra. Our model demonstrates that such GRHD accretion off the equatorial plane (i.e., v ≳ 0.1 c where c is the speed of light in the vicinity of AGN closer than ∼100 Schwarzschild radii) can manifest itself as UFIs in the form of a redshifted absorption signature assuming the observed characteristics such as column density of N H ∼ 10 23 cm −2 and ionization parameter of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>ξ</mml:mi> <mml:mo stretchy="false">[</mml:mo> <mml:mi mathvariant="normal">erg</mml:mi> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">cm</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">]</mml:mo> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>3</mml:mn> </mml:math> , as also seen in recent multiepoch NuSTAR observations among other data.