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. (December 2020) - Klimenko, V V
Abstract: Evolution of the cosmic microwave background (CMB) temperature with redshift T CMB = T CMB 0 × ( 1 + z ) 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.