Probing photon decay with the Sunyaev-Zel’dovich effect

¹ INAF – Osservatorio Astronomico di Roma via Frascati 33, 00040 Monteporzio, Italy
e-mail: sergio.colafrancesco@oa-roma.inaf.it
² School of Physics, University of the Witwatersrand, Private Bag 3, 2050- Johannesburg, South Africa
e-mail: sergio.colafrancesco@wits.ac.za

Received: 21 November 2013
Accepted: 14 December 2013

Abstract

Context. The fundamental properties of the photon have a deep impact on the astrophysical processes that involve it, such as the inverse Compton scattering of CMB photon by energetic electrons residing within galaxy cluster atmospheres. This is usually referred to as the Sunyaev-Zel’dovich effect (SZE).

Aims. We calculate the combined constraints on the photon decay time and mass by studying the impact of the modified CMB spectrum on the SZE of galaxy clusters.

Methods. We analyze the modifications of the SZE as produced by photon decay effects. We study the frequency ranges where these modifications are large and where the constraints derived from the SZE are stronger than those already obtained from the CMB spectrum.

Results. We show that the SZE can set limits on the photon decay time and mass, or on E^∗ = (t₀/τ_γ)m_γc² , which are stronger than those obtained from the CMB. The main constraints come from the low-frequency range ν ≈ 10−50 GHz where the modified SZE ΔI_mod is greater than the standard one ΔI, with the difference |(ΔI_mod − ΔI)| increasing with the frequency for increasing values of E^∗. Additional constraints can be set in the range 120−180 GHz where there is an increase in the frequency position of the minimum of ΔI_mod with respect to the standard one with increasing values of E^∗.

Conclusions. We demonstrated that the effect of photon decay can be measured or constrained by the Square Kilometer Array in the optimal range ≈ 10−30 GHz setting limits of E^∗ ≲ 1.4 × 10^-9 eV and 5 × 10^-10 eV for 30- and 260-h integration for A2163, respectively. These limits are tighter than those obtained with the COBE-FIRAS spectral measurements of the CMB.