Multiple Colliding Winds
In dense super star clusters a multitude of wind collisions occurs. A network of bubbles forms around the stars, which combine to create an extended medium of hot shocked gas. X-ray observations in the last 5 years have revealed that the temperature of the X-ray emitting gas is lower than expected. Various possibilities have been put forward, such as the mixing of large quantities of cold gas into the hot medium, but the issue is not yet resolved. Other key questions to address include the efficiency and timescale for the winds to clear out molecular material and the evolution of the rate at which mass and energy is deposited back into the surrounding galactic medium. This is important for understanding star formation and molecular cloud evolution on a galactic scale.
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Amongst the dense stellar clusters known in our Galaxy, the central cluster around Sgr A* is unusual in many respects, including the discovery of TeV emission. Various origins of the TeV emission have been proposed, including the central supermassive black hole, the young SNR Sgr A East, the dark matter halo, and from non-thermal particles accelerated at the multitude of colliding winds shocks. It is hoped that observations and theory will together advance a consensus on this issue in the coming years.