Volume 521, October 2010
|Number of page(s)||9|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||14 October 2010|
Comet-shaped sources at the Galactic center
Evidence of a wind from the central 0.2 pc
Physikalisches Institut, Universität zu Köln,
Zülpicher Str. 77,
50937 Köln, Germany e-mail: firstname.lastname@example.org
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3 Instituto de Astrofísica de Andalucía CSIC, Glorieta de la Astronoma S/N, 18008 Granada, Spain
Accepted: 31 May 2010
Context. In 2007 we reported two comet-shaped sources in the vicinity of Sgr A* (0.8” and 3.4” projected distance), named X7 and X3. The symmetry axes of the two sources are aligned to within 5° in the plane of the sky, and the tips of their bow shocks point towards Sgr A*. Our measurements show that the proper motion vectors of both features are pointing in directions more than 45° away from the line that connects them with Sgr A*. This misalignment of the bow-shock symmetry axes and their proper motion vectors, combined with the high proper motion velocities of several 100 km s-1, suggest that the bow shocks must be produced by an interaction with some external fast wind, possibly coming from Sgr A*, or from stars in its vicinity.
Aims. We have developed a bow-shock model to fit the observed morphology and constrain the source of the external wind.
Methods. The result of our modeling gives the best solution for bow-shock standoff distances for the two features, which allows us to estimate the velocity of the external wind, making certain that all likely stellar types of the bow-shock stars are considered.
Results. We show that neither of the two bow shocks (one of which is clearly associated with a stellar source) can be produced by the influence of a stellar wind of a single mass-losing star in the central parsec. Instead, an outflow carrying a momentum comparable to the one contributed by the ensemble of the massive young stars can drive shock velocities capable of producing the observed comet-shaped features. We argue that a collimated outflow arising perpendicular to the plane of the clockwise rotating stars (CWS) can easily account for the two features and the mini-cavity. However, the collective wind from the CWS has a scale of >10”. The presence of a strong, mass-loaded outbound wind at projected distances from Sgr A* of <1” in fact agrees with models that predict a highly inefficient accretion onto the central black hole owing to a strongly radius dependent accretion flow.
Key words: Galaxy: center / stars: mass-loss / infrared: stars / infrared: ISM
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.