The Impact of High Pressure Cluster Environment on the X-ray Luminosity of Coma Early-type Galaxies

We present an observational study of the Lx vs Lb sigma^2 relation for early-type galaxies in the Coma cluster based on the XMM-Newton survey data. Compared to a similar relation for a sample dominated by field early-type galaxies, the Coma cluster galaxies show a flatter slope. Our calculations show that adiabatic compression produces a flattening in the Lx vs Lb sigma^2 relation that is in remarkable agreement with the observed effect. Our scenario is further supported by the observed compactness of the X-ray emission of Coma galaxies.