A Hydrodynamical Thermal Irradiated Wind from the Outer Thin Accretion Disk in Low-luminosity Active Galactic Nuclei

2024/08/01 by Nagendra Kumar, Kumar, Nagendra
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)

paper · pdf · doi:10.48550/arxiv.2408.00485

openalex publication_date 2024/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31

Abstract

Evidently, low-luminosity active galactic nuclei (LLAGNs) are comprised of an inner advective disk and an outer geometrically thin disk. Wind is inevitable in LLAGNs, mainly interpreted in an indirect way, also the evidence is growing for the presence of wind in the outer thin disk. We present a hydrodynamics (HD) model for wind from the outer thin disk, where the main driver is the inner disk irradiation (which is parameterized by a number x in hydrostatic equilibrium equation) and the heating mechanism is photoionization. The model works for low-intensity irradiation or from a height z_s in the optically thin medium. We solve the model equations in cylindrical coordinates along the z-axis for a given radius r with assuming a tiny vertical speed v_z (≪ c_s sound speed). The sonic point conditions assure an isobaric regime above the sonic height (z^max); in addition to the height z_f (≪ z^max), the radial pressure gradient also supports the fluid rotation, and both jointly assure a wind ejection from the z^max with fluid speed. The z^max increases with x, and beyond a large z^max (say z^max_t corresponding to maximum x), there is no physical solution. We start the computation from the outer radius r_o^thin to the inner r_in^thin with a Bondi mass accretion rate M_Bondi, to explore the r dependency of the mass inflow rate M and wind properties. We constrain the model by fixing M at r_in^thin from the observations of NGC 1097 and check the feasibility of the model by comparing the energetics with the observed bolometric luminosity. The wind is an equatorial with a viewing angle i>85 degrees and capable to generate red/blueshifted lines, which would be a general characteristics for LLAGNs.

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