On the Formation of Compact Stellar Disks Around Sgr A*

TL;DR

This paper proposes that partial accretion of passing molecular clouds explains the formation, low angular momentum, and stellar properties of the young stellar disks around Sgr A*, providing a natural in-situ star formation scenario.

Contribution

It introduces a new model where cloud accretion explains the angular momentum and formation of stellar disks around Sgr A*.

Findings

Cloud accretion can produce low angular momentum disks.

Captured cloud material becomes gravitationally unstable and forms stars.

The model accounts for the eccentricity and inclinations of stellar orbits.

Abstract

The recent identification of one or two sub-parsec disks of young, massive stars orbiting the ~4e6 solar mass black hole Sgr A* has prompted an "in-situ" scenario for star formation in disks of gas formed from a cloud captured from the Galactic center environment. To date there has been no explanation given for the low angular momentum of the disks relative to clouds passing close to the center. Here we show that the partial accretion of extended Galactic center clouds, such as the 50 km/s giant molecular cloud, that temporarily engulf Sgr A* during their passage through the central region of the Galaxy provide a natural explanation for the angular momentum and surface density of the the observed stellar disks. The captured cloud material is gravitationally unstable and forms stars as it circularizes, potentially explaining the large eccentricity and range of inclinations of the observed stellar orbits. The application of this idea to the formation of the circumnuclear ring is also discussed.