Structure and Instability of the Ionization Fronts around Moving Black Holes

Understand

In this paper we focus on understanding the physical processes that lead to stable or unstable ionization fronts (I-fronts) observed in simulations of moving black holes (BHs).

• The front instability may trigger bursts of gas accretion, rendering the BH significantly more luminous than at steady-state.
• We perform a series of idealized three dimensional radiation hydrodynamics simulations resolving the I-fronts around BHs of mass $M_\mathrm{BH}$ and velocity $v_\infty$ accreting from a medium of density $n_\mathrm{H}$.
• The I-front, with radius $R_\mathrm{I}$, transitions from D-type to R-type as the BH velocity becomes larger than a critical value $v_\mathrm{R}\sim 40\,\mathrm{km/s}$.