# Anisotropic thermal Sunyaev-Zel'dovich effect and the possibility of an independent measurement of the CMB dipole, quadrupole and octupole

## TL;DR

This paper explores how anisotropic CMB radiation causes spectral distortions in the thermal Sunyaev-Zel'dovich effect, offering a new method to independently measure low-order CMB anisotropies and distinguish between SW and ISW effects using future high-sensitivity observations.

## Contribution

It derives corrections to the thermal SZ effect caused by low-order CMB multipoles and proposes using galaxy clusters to independently measure CMB anisotropies and differentiate SW and ISW effects.

## Key findings

- Derivation of correction terms for the thermal SZ effect due to CMB anisotropies.
- Proposal of a method to measure CMB dipole, quadrupole, and octupole independently.
- Potential for future observations with the Millimetron mission to detect these spectral distortions.

## Abstract

We consider the effect of the cosmic microwave background (CMB) frequency spectral distortions arising due to the Compton scattering of the anisotropic radiation on Sunyaev-Zel'dovich (SZ) clusters. We derive the correction to the thermal SZ effect due to the presence of multipoles with $\ell=1,2,3$ in the anisotropy of the CMB radiation. We show that this effect gives us an opportunity for an independent evaluation of the CMB dipole, quadrupole and octupole angular anisotropy in our location using distorted signal from the nearby galaxy clusters and to distinguish between the Sachs-Wolfe (SW) and the Integrated Sachs-Wolfe (ISW) effects by combining such signals from distant and nearby clusters. The future space mission 'Millimetron' will have unprecedented sensitivity, which will make it possible to observe the spectral distortion we are considering.