Workshop Participants (picture taken by Saliba F. Saliba)
The ISSI Workshop is devoted to an in-depth examination of complex astrophysical events with extreme energy release via multi-wavelength observations and modeling. Clusters of galaxies are the largest gravitationally bound structures in the Universe. Galaxy clusters now are one of the most important cosmological probes to test the standard cosmological models. Constrains on the Dark Energy equation of state from the cluster number density measurements, deviations from the Gaussian perturbation models, Sunyaev-Zeldovich effect as well as the dark matter profiles are among of the issues to be studied with clusters.
The baryonic composition of clusters is dominated by hot gas that is in quasi-hydrostatic equilibrium within the dark matter dominated gravitational potential well of the cluster. The hot gas is visible through spatially extended thermal X-ray emission, and it has been studied extensively both for assessing its physical properties and also as a tracer of the large scale structure of the Universe.
Magnetic fields as well as a number of non-thermal plasma processes play a role in clusters of galaxies as we observe from the radio observations by VLA, GMRT and LOFAR. A goal of the proposed workshop is to review those processes and to investigate how they are linked together. We will make use of the latest theoretical and observational developments in the field.
One of the aspects is the Sunyaev-Zeldovich effect in clusters. While frequently this effect is used for cosmological purposes, the signal can be used to get deeper insight into the distribution and properties of the hot gas in clusters, and we intend to discuss the implications of the findings of ESA’s Planck mission with respect to the cluster gas physics.
The amount of data on clusters of galaxies obtained with the XMM-Newton and Chandra satellites is still growing, and the missions have produced large, high quality samples of clusters. We will discuss also the findings obtained from the finest spectral imaging obtained by these satellites. The Suzaku X-ray satellite has provided a low-background view of the cluster outskirts. The Hitomi instrument has obtained the first X-ray spectrum of a galaxy cluster with an energy resolution sufficient to detect turbulence
Clusters of galaxies are not isolated entities in the Universe: they are connected through a filamentary cosmic web. Theoretical predictions indicate the way this web is evolving. In the early Universe most of the gas in the web was relatively cool (about 10,000 K). In the present Universe, however, about half of all the baryons are predicted to be in a warm phase (10(5)-10(7) K), the Warm-Hot Intergalactic Medium (WHIM), with temperatures intermediate between the hot clusters and the cool absorbing gas causing the Lyman-alpha forest. In cluster outskirts the connection to these structures can be studied. ESA’s Planck instrument found an extended bridge of hot gas connecting two clusters of galaxies Abell 399 and Abell 401, shedding light on the ‘missing baryons’ in the cluster vicinity.
These and other aspects of the observations and physics of clusters of galaxies will be discussed in the workshop and presented in the ISSI Springer book.
The Workshop will cover the following main themes:
The main goal of the proposed ISSI Workshop is to discuss the state of the art of the research and future prospective of studies of supernovae. Following discussions by the Conveners, it is proposed that the Workshop will cover the following main themes:
- Cosmology with clusters of galaxies
- Observations, theory and numerical simulations of: cluster mergers, central AGN / ICM interactions, cluster abundances, cluster turbulence, magnetic fields and non-thermal particles in clusters, plasma processes in clusters
- Interface between clusters and the cosmic web
Last update: November 22, 2017