Relativistic SZ maps and electron gas temperature spectroscopy

While third-generation CMB experiments have allowed to release the first maps of Compton-y distortion due to thermal Sunyaev-Zeldovich (SZ) effect, next-generation CMB experiments should allow us to map also the electron gas temperature, T_e, across the sky through the detection of relativistic corrections to the thermal SZ effect. We discuss about experimental requirements to break the y-T_e degeneracy of the observed SZ intensity, and propose a new component separation approach based on moment expansion to disentangle the y and T_e observables of the relativistic SZ effect while mitigating foregrounds. We show how our approach offers a new spectroscopic view of the clusters not only across frequencies but now also across temperatures. We also show how the relativistic electron temperature power spectrum provides a new cosmological observable which may complement the Compton-y map power spectrum to break some of the parameter degeneracies in future cosmological SZ analyses.