Universität zu Köln

Muzic, K., Eckart, A., Schoedel, R., Buchholz, R., Zamaninasab, M. and Witzel, G. (2010). Comet-shaped sources at the Galactic center Evidence of a wind from the central 0.2 pc. Astron. Astrophys., 521. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 0004-6361

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Abstract

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 degrees 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 degrees 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.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Muzic, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Eckart, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schoedel, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Buchholz, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zamaninasab, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Witzel, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-494981
DOI:	10.1051/0004-6361/200913087
Journal or Publication Title:	Astron. Astrophys.
Volume:	521
Date:	2010
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	0004-6361
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language HERBIG AE/BE STARS; INTERMEDIATE-MASS STARS; SAGITTARIUS-A-ASTERISK; STELLAR ORBITS; BLACK-HOLE; BOW SHOCKS; CENTRAL PARSEC; YOUNG STARS; LINEAR-POLARIZATION; MILKY-WAY Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/49498