A universal correlation between warm and hot gas in the stripped tails of cluster galaxies

The impact of ram pressure stripping on galaxy evolution is well known (for example, ref. 1). Recent multi-wavelength data have revealed many examples of galaxies undergoing stripping, often accompanied with multi-phase tails2–13. As energy transfer in the multi-phase medium is an outstanding question in astrophysics, galaxies in stripping are great objects to study. Despite the recent burst of observational evidence, the relationship between gas in different phases in the tails is poorly known. Here we report a strong linear correlation between the X-ray surface brightness and the Hα surface brightness of the diffuse gas in the stripped tails at ~10–40 kpc scales, with a slope of ~3.5. This discovery provides evidence for the mixing of the stripped interstellar medium with the hot intra-cluster medium as the origin of the multi-phase tails. The established relation in stripped tails, also in comparison with the probably related correlations in similar environments such as galactic winds and X-ray cool cores, provides an important test for models of energy transfer in the multi-phase gas. It also indicates the importance of the Hα data to study clumping and turbulence in the intra-cluster medium.