Entropy Driven Winds: Outflows and Fountains Lifted Gently by Buoyancy

Understand

We present a new theoretical framework for using entropy to understand how outflows driven by supernovae are launched from disc galaxies: via continuous, buoyant acceleration through the circumgalactic medium (CGM).

• When young star clusters detonate supernovae in the interstellar medium (ISM) of a galaxy, they generate hot, diffuse bubbles that push on the surrounding ISM and evaporate that ISM into their interiors.
• As these bubbles reach the scale height of the ISM, they break out of the disc, rising into the CGM.
• Once these bubbles break out, if they have sufficiently high entropy, they will feel an upward acceleration, owing to a local buoyant force.