English

Pericenter passage of the gas cloud G2 in the Galactic Center

Astrophysics of Galaxies 2015-06-16 v1

Abstract

We have further followed the evolution of the orbital and physical properties of G2, the object currently falling toward the massive black hole in the Galactic Center on a near-radial orbit. New, very sensitive data were taken in April 2013 with NACO and SINFONI at the ESO VLT . The 'head' of G2 continues to be stretched ever further along the orbit in position-velocity space. A fraction of its emission appears to be already emerging on the blue-shifted side of the orbit, past pericenter approach. Ionized gas in the head is now stretched over more than 15,000 Schwarzschild radii RS around the pericenter of the orbit, at ~ 2000 RS ~ 20 light hours from the black hole. The pericenter passage of G2 will be a process stretching over a period of at least one year. The Brackett-{\gamma} luminosity of the head has been constant over the past 9 years, to within +- 25%, as have the line ratios Brackett-{\gamma} / Paschen-{\alpha} and Brackett-{\gamma} / Helium-I. We do not see any significant evidence for deviations of G2's dynamical evolution, due to hydrodynamical interactions with the hot gas around the black hole, from a ballistic orbit of an initially compact cloud with moderate velocity dispersion. The constant luminosity and the increasingly stretched appearance of the head of G2 in the position-velocity plane, without a central peak, is not consistent with several proposed models with continuous gas release from an initially bound zone around a faint star on the same orbit as G2.

Keywords

Cite

@article{arxiv.1306.1374,
  title  = {Pericenter passage of the gas cloud G2 in the Galactic Center},
  author = {Stefan Gillessen and Reinhard Genzel and Tobias K Fritz and Frank Eisenhauer and Oliver Pfuhl and Thomas Ott and Marc Schartmann and Alessandro Ballone and Andreas Burkert},
  journal= {arXiv preprint arXiv:1306.1374},
  year   = {2015}
}

Comments

10 figures, submitted to ApJ