AGN Outflow Shocks on Bonnor-Ebert Spheres

TL;DR

This study uses hydrodynamic simulations to explore how AGN winds impact star formation in Bonnor-Ebert spheres, revealing that ram pressure determines whether star formation is triggered or suppressed.

Contribution

It provides new insights into the effects of AGN wind parameters on star formation, highlighting the threshold ram pressure for cloud collapse and the potential for both positive and negative feedback within galaxies.

Findings

High ram pressure winds increase fragmentation and shorten star formation timescales.

A threshold ram pressure of ~2×10⁻⁸ dyne/cm² prevents star formation by disrupting cloud collapse.

AGN wind parameters vary spatially, enabling simultaneous positive and negative feedback.

Abstract

Feedback from Active Galactic Nuclei (AGN) and subsequent jet cocoons and outflow bubbles can have a significant impact on star formation in the host galaxy. To investigate feedback physics on small scales, we perform hydrodynamic simulations of realistically fast AGN winds striking Bonnor-Ebert (BE) spheres and examine gravitational collapse and ablation. We test AGN wind velocities ranging from 300--3,000 km s$^{-1}$ and wind densities ranging from 0.5--10 $m_\mathrm{p}\,\mathrm{cm}^{-3}$. We include heating and cooling of low- and high-temperature gas, self-gravity, and spatially correlated perturbations in the shock, with a maximum resolution of 0.01 pc. We find that the ram pressure is the most important factor that determines the fate of the cloud. High ram pressure winds increase fragmentation and decrease the star formation rate, but also cause star formation to occur on a much shorter time scale and with increased velocities of the newly formed stars. We find a threshold ram pressure of $\sim 2\times10^{-8}$ dyne cm$^{-2}$ above which stars are not formed because the resulting clumps have internal velocities large enough to prevent collapse. Our results indicate that simultaneous positive and negative feedback will be possible in a single galaxy as AGN wind parameters will vary with location within a galaxy.