2025PASP..137f4104K

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 assuming a tiny vertical speed v_z (≪c_s sound speed). The sonic point conditions assure an isobaric regime above the sonic height (${z}^{{\rm{\max }}}$); in addition to the height ${z}_{f}(\ll {z}^{{\rm{\max }}}$), the radial pressure gradient also supports the fluid rotation, and both jointly assure a wind ejection from the ${z}^{{\rm{\max }}}$ with fluid speed. The ${z}^{{\rm{\max }}}$ increases with x, and beyond a large ${z}^{{\rm{\max }}}$ (say ${z}_{t}^{{\rm{\max }}}$ corresponding to maximum x), there is no physical solution. We start the computation from the outer radius ${r}_{o}^{{\rm{thin}}}$ to the inner ${r}_{{\rm{in}}}^{{\rm{thin}}}$ with a Bondi mass accretion rate ${\dot{M}}_{{\rm{Bondi}}}$ to explore the r dependency of the mass inflow rate $\dot{M}$ and wind properties. We constrain the model by fixing $\dot{M}$ at ${r}_{{\rm{in}}}^{{\rm{thin}}}$ 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 equatorial with a viewing angle i > 85° and capable of generating red/blueshifted lines, which would be a general characteristics for LLAGNs.