X-ray ETGs properties in the Chandra COSMOS survey

In the local universe, a tight, steep relationship has been established between these two quantities (L_x.gas_ ~ L_K_^4.5^), suggesting the presence of largely virialized halos in X-ray luminous systems.

We use well-established relations from the study of local universe ETGs, together with the expected evolution of the X-ray emission, to subtract the contribution of low-mass X-ray binary populations from the X-ray luminosity of our sample. Our selection minimizes the presence of active galactic nuclei (AGNs), yielding a sample representative of normal passive COSMOS ETGs; therefore, the resulting luminosity should be representative of gaseous halos, although we cannot exclude other sources such as obscured AGNs or enhanced X-ray emission connected with embedded star formation in the higher-z galaxies.