Star Formation in the vicinity of Nuclear Black Holes: Young Stellar Objects close to Sgr A*

TL;DR

This study uses 3D hydrodynamical simulations to demonstrate that star formation can occur near supermassive black holes like Sgr A* due to orbital compression of molecular clumps, explaining young stars close to the black hole.

Contribution

The paper introduces a model showing how molecular clumps can form stars near black holes through orbital compression, challenging previous assumptions about star formation suppression.

Findings

Orbital compression increases gas density beyond tidal limits near Sgr A*

Star formation is possible in highly eccentric molecular clumps

The model explains the origin of young stars close to the black hole

Abstract

It is often assumed that the strong gravitational field of a super-massive black hole disrupts an adjacent molecular cloud preventing classical star formation in the deep potential well of the black hole. Yet, young stars have been observed across the entire nuclear star cluster of the Milky Way including the region close ($<$0.5~pc) to the central black hole, Sgr A*. Here, we focus particularly on small groups of young stars, such as IRS 13N located 0.1 pc away from Sgr A*, which is suggested to contain about five embedded massive young stellar objects ($<$1 Myr). We perform three dimensional hydrodynamical simulations to follow the evolution of molecular clumps orbiting about a $4\times10^6~M_{\odot}$ black hole, to constrain the formation and the physical conditions of such groups. The molecular clumps in our models assumed to be isothermal containing 100 $M_{\odot}$ in $<$0.2 pc radius. Such molecular clumps exist in the circumnuclear disk of the Galaxy. In our highly eccentrically orbiting clump, the strong orbital compression of the clump along the orbital radius vector and perpendicular to the orbital plane causes the gas densities to increase to values higher than the tidal density of Sgr A*, which are required for star formation. Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust enshrouded star that may have been formed recently through the mechanism supported by our models.