The warped young stellar disc in the Galactic centre

¹ Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Praha, Czech Republic e-mail: subr@sirrah.troja.mff.cuni.cz
² Astronomical Institute, Academy of Sciences, Boční II, 14131 Praha, Czech Republic
³ Argelander Institute for Astronomy (AIfA), Auf dem Hügel 71, 53121 Bonn, Germany

Received: 2 October 2008
Accepted: 25 November 2008

Abstract

Aims. Within the central parsec of the Galaxy, several dozen young stars orbiting a central supermassive black hole are observed. A subset of these stars forms a coherently rotating disc. Other observations reveal a massive molecular torus that lies at a radius ~ from the centre. In this paper we consider the gravitational influence of the molecular torus upon the stars of the stellar disc.

Methods. We derive an analytical formula for the rate of precession of individual stellar orbits and we show that it is highly sensitive to the orbital semi-major axis and inclination with respect to the plane of the torus, as well as to the mass of the torus.

Results. Assuming that both the stellar disc and the molecular torus are stable on the timescale ≳, we constrain the mass of the torus and its inclination with respect to the young stellar disc. We further suggest that all young stars observed in the Galactic centre may have a common origin in a single coherently rotating structure with an opening angle ≲, which was partially destroyed (warped) during its lifetime by the gravitational influence of the molecular torus.