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Measuring the CMB temperature at high redshift to test the standard Lambda-CDM prediction Tcmb=T0(1+z)

Ricardo T. Génova-Santos
Instituto de Astrofísica de Canarias

One of the most precise measurements in modern cosmology is the CMB temperature at z=0 derived from COBE-FIRAS data taken 30 years ago. However, measurements of the CMB temperature at high redshift are not abundant, despite the obvious cosmological interest in verifying the standard redshift-evolution Tcmb(z)=T0(1+z), which originates in the framework of the LambdaCDM scenario under the assumptions of adiabatic expansion of the Universe and photon-number conservation. There are several-non-standard scenarios where these conditions are not met, leading to deviations from the standard evolution. Until now two different techniques have been used to obtain high-z measurements of the CMB temperature:
i) the Sunyaev-Zel'dovich effect in high-z galaxy clusters, which has led to estimates up to z~1 with a precision of ~0.5 K, and
ii) asborption lines involving energy levels that have been excited by the CMB radiation, which have allowed to reach redshifts ~2-3 with precision sometimes better than 1 K.
In this talk I will explain these techniques, discuss their pros and cons, review current best measurements and constraints, and discuss prospects to obtain more precise measurements in the future.

2019 November 21, 15:00

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia