What external force strips a galaxy's cooler gas reservoir as it moves through the intracluster medium?

Answer

Ram pressure stripping

Ram pressure stripping occurs when a galaxy plows through the hot gas permeating a cluster, with this medium acting like a powerful wind that physically removes the cooler gas disk.

What external force strips a galaxy's cooler gas reservoir as it moves through the intracluster medium?
galaxystructuretimegravitydark matter