The measurements of the CMB temperature in diffuse interstellar medium of the Milky-Way and high redshift galaxies based on excitation of CI fine-structure and H2 rotational levels

Abstract

Evolution of the cosmic microwave background (CMB) temperature with redshift is predicted by the standard ΛCDM cosmological model and has been confirmed by measurements of the Sunyaev-Zel’dovich effect in Plank data (at z ≤ 1) and excitation of CO rotational levels in quasar spectra (at 1.7 ≤ z ≤ 2.7). Excitation of the fine-structure levels of neutral carbon (CI) is also sensitive to the temperature of the CMB radiation. However collisions and UV pumping lead to a significant degeneracy of the fitting parameters, since poor data on physical conditions. We found that a joint fit to excitation of low H2 rotational and CI fine-structure levels can break this degeneracy and provide a tighter constraints on the T CMB. We present estimates of the T CMB derived from excitation of CI fine-structure levels in the Milky Way clouds and high redshift absorption systems.