An international team of astronomers has, for the first time, used the NOEMA interferometer to detect the thermal Sunyaev–Zel’dovich (tSZ) effect in the distant galaxy cluster CL J1226.9+3332, nearly 7 billion light-years away (read Muñoz-Echeverría M. et al., 2025). By mapping the tSZ signal at unprecedented resolution, NOEMA revealed that the cluster’s hot gas has a surprisingly flat pressure profile, instead of peaking at the center as expected. This suggests the cluster is still settling after past mergers, offering a glimpse into the turbulent early Universe.
These high-resolution observations trace the intracluster gas down to just 15 kpc (~50,000 light-years), complementing earlier X-ray and tSZ measurements to give a full picture of pressure from the core out to 1.5 Mpc (~5 million light-years). This breakthrough shows that NOEMA can resolve the hot plasma in distant clusters, opening new avenues to study how galaxies, black holes, and cosmic feedback shape the largest structures in the cosmos.
Read the full NOEMA press release.
Image: Thermal Sunyaev–Zel’dovich (tSZ) effect detected by NOEMA toward the distant galaxy cluster CL J1226.9+3332. The dark blue and black region at the centre shows the tSZ signal, a dimming of the cosmic microwave background (CMB) caused by scattering from the hot electrons that fill the cluster. These high-resolution NOEMA observations trace the pressure of the intracluster gas down to scales of about 15 kpc, revealing a surprisingly flat pressure profile in the cluster’s core. (see publication)