Magnetohydrodynamic Simulations of a Plunging Black Hole into a Molecular Cloud

TL;DR

This study uses magnetohydrodynamic simulations to explore how a black hole plunging into a molecular cloud can produce observable features like the Bullet in W44, supporting the shooting model hypothesis.

Contribution

It demonstrates that black hole plunging scenarios can reproduce observed molecular cloud features, providing new insights into black hole-cloud interactions.

Findings

The accelerated gas region is much larger than the classical Bondi-Hoyle-Lyttleton radius.

Simulation results match the observed 'Y' shape in position-velocity maps of the Bullet.

The size of the simulated Bullet aligns with observations within an order of magnitude.

Abstract

Using two-dimensional magnetohydrodynamic simulations, we investigated the gas dynamics around a black hole plunging into a molecular cloud. In these calculations, we assumed a parallel-magnetic-field layer in the cloud. The size of the accelerated region is far larger than the Bondi-Hoyle-Lyttleton radius, being approximately inversely proportional to the Alfv\'en Mach number for the plunging black hole. Our results successfully reproduce the "Y" shape in position velocity maps of the "Bullet" in the W44 molecular cloud. The size of the Bullet is also reproduced within an order of magnitude using a reasonable parameter set. This consistency supports the shooting model of the Bullet, according to which an isolated black hole plunged into a molecular cloud to form a compact broad-velocity-width feature.