Cometary shaped sources at the Galactic Center - Evidence for a wind from the central 0.2 pc - Astrophysics > Astrophysics of GalaxiesReport as inadecuate




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Abstract: In 2007 we reported two cometary shaped sources in the vicinity of Sgr A*0.8- and 3.4- projected distance, named X7 and X3. The symmetry axes of thetwo sources are aligned to within 5 degrees in the plane of the sky and thetips of their bow-shocks point towards Sgr A*. Our measurements show that theproper motion vectors of both features are pointing in directions more than 45deg away from the line that connects them with Sgr A*. This misalignment of thebow-shock symmetry axes and their proper motion vectors, combined with the highproper motion velocities of several 100 km-s, suggest that the bow-shocks mustbe produced by an interaction with some external fast wind, possibly comingfrom Sgr A*, or stars in its vicinity. We have developed a bow-shock model tofit the observed morphology and constrain the source of the external wind. Theresult of our modeling allows us to estimate the velocity of the external wind,making sure that all likely stellar types of the bow-shock stars areconsidered. We show that neither of the two bow-shocks one of which is clearlyassociated with a stellar source can be produced by influence of a stellarwind of a single mass-losing star in the central parsec. Instead, an outflowcarrying a momentum comparable to the one contributed by the ensemble of themassive young stars, can drive shock velocities capable of producing theobserved cometary features. We argue that a collimated outflow arisingperpendicular to the plane of the clockwise rotating stars CWS, can easilyaccount for the two features and the mini-cavity. However, the collective windfrom the CWS has a scale of >10-. The presence of a strong, mass-loadedoutbound wind at projected distances from Sgr A* of <1- is in fact inagreement with models that predict a highly inefficient accretion onto thecentral black hole due to a strongly radius dependent accretion flow.



Author: K. Muzic, A. Eckart, R. Schoedel, R. Buchholz, M. Zamaninasab

Source: https://arxiv.org/







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