Ram-pressure stripping

Ram-pressure stripping removes gas from a galaxy as it moves through hot gas in its surroundings. The process can suppress star formation by depriving the galaxy of the material needed to form stars.

Ram pressure: The pressure exerted on an object moving through a fluid, proportional to the fluid’s density and the square of the object’s speed. It is the external force that pushes a galaxy’s gas out of its gravitational potential.
Star formation: The process by which dense regions of interstellar gas collapse to form stars. Removing cold gas can reduce the fuel available for new stars.
ESO 137-001: A spiral galaxy in the Norma Cluster with long X-ray and H-alpha tails of stripped material. Its bright, multiphase tails provide a well-studied example of ongoing stripping.
Tidal stripping: The removal of stars or gas from a galaxy by gravitational forces exerted by another system. It removes material through gravity rather than pressure from ambient gas.
Magnetic draping: The amplification and alignment of magnetic fields around an object moving through a magnetized plasma. Draped fields may alter heat transfer and the stability of stripped gas.
Gunn–Gott criterion: A condition estimating when ram pressure exceeds a galaxy’s gravitational restoring force per unit area. It predicts whether the surrounding gas can displace gas in a galaxy’s disk.
Galaxy quenching: The cessation or substantial decline of star formation in a galaxy. Stripping can quench a galaxy by removing its star-forming gas supply.
Virgo Cluster: The nearest large galaxy cluster, centered about 16.5 megaparsecs from the Milky Way. Its galaxies include nearby examples of gas removal in a cluster environment.
Galaxy harassment: Repeated high-speed gravitational encounters that distort and heat galaxies in dense environments. It can alter galaxies through encounters even without direct gas pressure.
Thermal conduction: The transfer of thermal energy through particle interactions within or between materials. Its efficiency affects whether stripped cold gas survives in the hot medium.

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