# Gas Inflow and Star Formation near Supermassive Black Holes: The Role of Nuclear Activity

## TL;DR

This study uses advanced 3D simulations to investigate how active galactic nucleus radiation affects gas inflow and star formation near supermassive black holes, finding that moderate radiation does not prevent star formation.

## Contribution

First 3D radiative hydrodynamic simulations of gas inflow onto SMBHs incorporating AGN radiation effects, analyzing impact on disc formation and gravitational instability.

## Key findings

- UV radiation pressure inhibits inflow at high luminosities
- Central gas discs can form despite AGN feedback at low to moderate radiation levels
- Mass accretion rates are consistent with observed Eddington ratios

## Abstract

Numerical models of gas inflow towards a supermassive black hole (SMBH) show that star formation may occur in such an environment through the growth of a gravitationally unstable gas disc. We consider the effect of nuclear activity on such a scenario. We present the first three-dimensional grid-based radiative hydrodynamic simulations of direct collisions between infalling gas streams and a $4 \times 10^6~\text{M}_\odot$ SMBH, using ray-tracing to incorporate radiation consistent with an active galactic nucleus (AGN). We assume inflow masses of $ \approx 10^5~\text{M}_\odot$ and explore radiation fields of 10% and 100% of the Eddington luminosity ($L_\text{edd}$). We follow our models to the point of central gas disc formation preceding star formation and use the Toomre Q parameter ($Q_T$) to test for gravitational instability. We find that radiation pressure from UV photons inhibits inflow. Yet, for weak radiation fields, a central disc forms on timescales similar to that of models without feedback. Average densities of $> 10^{8}~\text{cm}^{-3}$ limit photo-heating to the disc surface allowing for $Q_T\approx1$. For strong radiation fields, the disc forms more gradually resulting in lower surface densities and larger $Q_T$ values. Mass accretion rates in our models are consistent with 1%--60% of the Eddington limit, thus we conclude that it is unlikely that radiative feedback from AGN activity would inhibit circumnuclear star formation arising from a massive inflow event.