Spitzer, VLA, and CFHT MegaCam image of Arp 94, also known as NGC 3226 and NGC 3227.
The grayscale Canada France Hawaii Telescope image shows visible starlight. Blue is cool hydrogen gas in radio light from the Very Large Array. Red is warm gas and dust in infrared light from Spitzer.
The blue filament of warm gas floods into the top galaxy shuts down star formation.
Credit: NASA, CFHT, NRAO, JPL-Caltech, Duc, Cuillandre
Source: https://www.spitzer.caltech.edu/image/sig14-029a-a-flood-of-gas