A multi-scale view of structure evolution in the Universe – MULTIVERSE

We will focus on the following tightly-linked, cutting-edge topics:

1. Test our understanding of the dark matter collapse at cluster scales from the evolution of the dark matter profile in these objects from X-ray follow-up of massive clusters newly detected by Planck

2. Disentangle and understand the respective role of gravitational and each non gravitational process (cooling and various galaxy feedbacks) in shaping the properties of the intra-cluster gas from quantification of the evolution of its X-ray and SZ scaling and structural properties compared to numerical simulations.

3. Characterise the distribution of diffuse baryons form the surrounding of clusters amd groups to large scales and provide new observational constraints on bulk flow motions, a signature of the large scale structure formation and evolution, from cross-correlation analysis of CMB maps and galaxy surveys.

4. Undertake the first systematic search and study from the Planck survey of the population of the progenitors of galaxy clusters via the IR/sub-mm properties of their dusty star forming galaxies. Compare their properties to these found in the most massive formed clusters at lower redshifts. The relatively unknown population of proto-clusters remains a missing link in the context of massive halo formation.

* First characterisation of the distribution of thermal pressure in clusters of galaxies (Planck Coll. 2013).

* First catalogue of clusters of galaxies from the Planck all-sky nominal survey (Planck Coll. 2013).

* Characterisation of the scaling properties of the cluster population detected by planck (Planck Coll. 2013).

* Cosmological constraints derived from cluster counts as seen by Planck (Planck Coll. 2014).

* Measurement of the T_CMB evolution from the Sunyaev-Zel'dovich effect (Hurier et al. 2013).

* First observation of the thermal Sunyaev-Zel'dovich effect with Kinetic Inductance Detectors (Adam et al. 2014).

* Planck: Optical identification and redshifts of Planck clusters with the RTT150 telescope

* Modeling the cross power spectrum of Sunyaev-Zel’dovich and X-ray surveys (Hurier et al. 2014).

* Contribution to the scientific exploitation of the full survey from the Planck mission

* Scientific esploitation of the folow-ups of Planck clusters through large programs (e.g., ESO, ITP, XMM)

* 24 publications from the project (ie, focusing on the scientific goals of the MULTIVERSE project, and which are the direct result of our project work).

* 25 publications that relate to the project (ie, publications contributed by the MULTIVERSE members and whihc science topic is connected MULTIVERSE).

* 37 presentations in conferences (invited and contributed) directly related to the MULTIVERSE project.

The distribution of visible matter in today’s Universe exhibits considerable structure. Most of the stars are organised in galaxies; galaxies in turn accumulate along large scale filaments and sheets, separated by bubble-like voids, defining a complex 3-D structure often called the “Cosmic Web”. At the intersection of filaments, effectively defining the nodes of the Cosmic Web, lie the galaxy clusters. The formation and evolution of all of this structure is a central issue of present-day cosmology. Cosmology has made spectacular progress in recent years, from concordant measurements of the cosmological parameters, showing that we live in a dark-matter, dark-energy dominated Universe, to the characterisation of the initial density fluctuations. We now have a robust model of the dark matter structure assembly from initial fluctuations, under the effect of gravitation. However, few direct observational constraints are available. Furthermore, we lack an understanding of the evolution of the baryonic component of the Universe, which is subject to complex additional physical processes linked to cooling and galaxy formation such as energy feedback from stellar explosions and accreting black holes. In addition, we do not even have a complete census of the baryons in the local Universe, where half of the mass, that has not been detected to-date, is believed to lie in filamentary structure. Present observations and theoretical work indicate that baryonic structure formation on various scales is deeply interconnected: galaxy formation depends on the large scale environment in which most galaxies are found, and on the physical properties of the intergalactic gas from which they form; this gas in turn is affected by galaxy feedback. Our project aims at providing new insight into the physics of structure formation through a multi-scale approach probing the evolution of matter in large structures, from the first assembly of galaxies around the largest over-densities in the initial density field, to the population of groups and clusters comprising today’s cosmic web and the filamentary structures that link them.

Using novel datasets over a wide range of wavelengths from X-rays to millimetre (e.g., XMM, Herschel, Planck, ALMA observations), and state of the art numerical simulations of structure formation, and by developing original analysis and statistical tools, we will focus on the following tightly-linked, cutting-edge topics:

1- Test our understanding of the dark matter collapse at cluster scales from the evolution of the dark matter profile in these objects from X-ray follow-up of massive clusters newly detected by Planck

2- Disentangle and understand the respective role of each non gravitational process (cooling and various galaxy feedbacks) in shaping the properties of the intra-cluster gas from quantification of the evolution of its scaling and structural properties compared to numerical simulations.

3- Characterise the distribution of diffuse baryons form the surrounding of clusters amd groups to large scales and provide new observational constraints on bulk flow motions, a signature of the large scale structure formation and evolution, from cross-correlation analysis of CMB maps and galaxy surveys.

4- Undertake the first systematic search and study from the Planck survey of the population of the progenitors of galaxy clusters via the IR/sub-mm properties of their dusty star forming galaxies. Compare their properties to these found in the most massive formed clusters at lower redshifts. The relatively unknown population of proto-clusters remains a missing link in the context of massive halo formation.

The derived observational constraints and products of our project will be important for cosmological applications (e.g constraints on the dark energy equation of state) and will open new ways for studies testing alternative cosmologies