ALMA's ability to see a 'cosmic hole' confirmed
https://phys.org/news/2017-03-alma-ability-cosmic-hole.html
Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) successfully imaged a radio "hole" around a galaxy cluster 4.8 billion light-years away.
This is the highest resolution image ever taken of such a hole caused by the Sunyaev-Zel'dovich effect (SZ effect). The image proves ALMA's high capability to
investigate the distribution and temperature of gas around galaxy clusters through the SZ effect.
A research team led by Tetsu Kitayama, Toho University, Japan, and Eiichiro Komatsu, Max Planck Institute for Astrophysics, Germany, used ALMA to investigate the hot
gas in a galaxy cluster. The hot gas is a key component to understand the nature and evolution of galaxy clusters. Even though the hot gas does not emit radio waves
itself, which would be detectable with ALMA, the gas scatters the radio waves of the Cosmic Microwave Background and makes a "hole" around the galaxy cluster. This
is called the Sunyaev-Zel'dovich effect (Note).
The team observed the galaxy cluster RX J1347.5-1145 located 4.8 billion light-years away. This galaxy cluster is well known among astronomers for its strong SZ
effect and has been observed many times with radio telescopes. These observations revealed an uneven distribution of the hot gas in this galaxy cluster, which was
not seen in X-ray observations. Astronomers therefore needed higher resolution observations; these however, were difficult to obtain with high-resolution radio
interferometers as the hot gas in galaxy clusters is relatively smooth and widely-distributed.