Hot, thermal electrons in galaxy clusters up-scatter the cosmic microwave background photons, making clusters visible in the microwave sky. This effect, known as the Sunyaev-Zeldovich effect, has been detected routinely toward individual galaxy clusters. Since the SZ effect is proportional to a projected thermal pressure of gas, we can use this effect to map all hot gas pressure in the Universe in projection. We start this talk by presenting the first image of the SZ effect obtained by ALMA, which has the highest spatial (both angular and physical) resolution ever achieved for the SZ mapping observations. With such a high resolution map comparable to X-ray maps, this SZ map enables us to study astrophysics of galaxy clusters in a new way. The second part of the talk concerns a full-sky map of the SZ effect. Thanks to its multi-frequency coverage from space, ESA’s Planck satellite has produced, for the first time, a full-sky map of the SZ effect. Statistics of this map, such as one-point PDF and the power spectrum, provides a powerful test of our theory for structure formation in the Universe. Unlike gravitational lensing of the CMB, which probes structure formation of the total matter, the statistics of the SZ effect tests our understanding of baryonic structure formation on large scales. We present state-of-the-art simulation of the SZ effect, and discuss what we learned from comparing the simulation with the Planck data. In the last part of the talk, we present a new analytical model for non-thermal gas pressure on galaxy clusters, which plays a crucial role in physical understanding of what we see in simulations and observations of the SZ effect.

References:

1. Kitayama, et al., “The Sunyaev-Zel’dovich effect at five arc-seconds: RX J1347.5-1145 imaged by ALMA”, arXiv:1607.08833 (accepted for publication in PASJ)

2. Dolag, Komatsu & Sunyaev, “SZ effects in the Magneticum Pathfinder Simulation: Comparison with the Planck, SPT, and ACT results”, arXiv:1509.05134 (accepted for publication in MNRAS)

3. Shi & Komatsu, “Analytical model for non-thermal pressure in galaxy clusters”, MNRAS, 445, 2574 (2014)