Hot Intergalactic Gas in Clusters of Galaxies

Clusters of galaxies are the most massive objects in our Universe. Each of them contains dark matter, thousands of galaxies and is filled with hot intergalactic gas radiating in X-rays.

Unusual method to detect clusters of galaxies is possible due to presence of extremely isotropic Cosmic Microwave Background Radiation (CMB) filling our Universe. Interaction of hot electrons with CMB photons changes the CMB spectrum in the directions toward clusters of galaxies. As a result clusters become “negative sources” of radiation in cm and mm spectral bands. The brightness and spectrum of these sources does not depend on distance or redshift. This property opens the way to detect all massive (M 2 > 10^14 Msun) clusters of galaxies (more than 100 000 !!!) in the observable Universe.

Planck spacecraft, ground based South Pole Telescope and Atacama Cosmology Telescope discovered recently more than thousand of extremely massive clusters of galaxies at different redshifts looking for such “negative sources” on microwave sky. This new discoveries opened new doors for observational cosmology. They are providing us with unique data on properties of our Universe as a whole, about its past and even future. It gives us clues about the physics working under the conditions and scales which we cannot test in the ground based laboratories.

In 2014 Russia is going to launch to L2 point of the Solar System the Spectrum-X spacecraft with German eRosita and Russian ART-XC telescopes with grazing incidence X-Ray optics. SRG/eRosita is designed to be able to detect 100 000 clusters of galaxies on the whole sky during 4 year long all sky survey. In addition more than 3 Mln AGNs, 30 000 star forming galaxies, 100 000 accreting white dwarfs and rapidly rotating stars with active hot coronae should be discovered during this sky survey.

06/03/2013 - 13:30
Prof. Rashid Sunyaev
Max-Planck-Institut für Astrophysik