The thermal Sunyaev-Zeldovich effect of primordial recombination radiation

Abstract

It is well known that recombination radiation of primordial hydrogen-helium plasma leads to the distortions of the Planckian spectrum shape of the cosmic microwave background (CMB) radiation. We discuss the thermal Sunyaev-Zeldovich (SZ) effect with taking into account primordial recombination radiation (PRR). Since in the thermal SZ effect the redistribution of the photons depends on the derivatives of the spectrum, the value of relative correction to SZ effect due to PRR is significantly larger than relative corrections due to PRR to the initial spectrum. Calculations of corrections to the thermal SZ effect due to PRR show that depending on the cluster parameters: (1) In the range of frequencies ν = 0.3-700 GHz, where CMB dominates and spectrum is very close to the Planckian one, the relative corrections due to PRR have an order of 10-9-10-6 of classical SZ effect (i.e. SZ effect for Planckian CMB spectrum). The difference of temperature deviations arising due to PRR coming from different directions (through intracluster and near intercluster medium) reaches values up to 7.6 nKcmb at ν ≃ 0.307 GHz (maximum in considered range). (2) In the range of frequencies ν = 700-5000 GHz, where cosmic infrared background (CIB) becomes significant or even dominates, the relative corrections due to PRR can reach 10-8-10-5 of main SZ effect (i.e. SZ effect for CIB). Corresponding intensity difference reaches values up to 25 mJy sr-1 (at ν ≃ 1700 GHz). In addition we suggest a modification of the method of electron gas temperature determination using corrections of the SZ effect due to PRR. Such modification allows one to simplify the determination of the cluster electron gas temperature in comparison with known methods.