In the quarter century since their first firm detection by the COBE satellite, Cosmic Microwave Background (CMB) anisotropies and galaxy clustering measurements have revolutionized the field of cosmology with an enormous impact on several branches of astrophysics and particle physics. From observations made by ground-based and satellite experiments a cosmological "concordance" model has emerged, in which the need for new physics beyond the standard model of particle physics is blatantly evident. For example, the Cold Dark Matter (CDM, hereafter) density is now constrained with a 1.25 % accuracy using recent CMB measurements, naively yielding an evidence for CDM at about 80 standard deviations. Cosmology is indeed extremely powerful in identifying CDM, since on cosmological scales the gravitational effect of CDM are cleaner and can be precisely discriminated from those of standard baryonic matter. Currently no other sector of physics aside from cosmology shows the need for CDM to such a level of significance. In this project we propose to make use of the most recent cosmological data to further constrain the nature of dark matter. In particular we will provide constraints on several dark matter candidates as massive neutrinos, neutralinos and axions. New exotic proposal in which modifications to general relativity can mimic dark matter as TeVeS or emergent gravity will be tested. We will also provide forecasts of the future constraints achievable by future experiments. We will make use of three main cosmological observables: CMB, weak lensing and cluster of galaxies.
This proposal comes therefore at unique time in cosmology. Our group is well known in the community for its expertise in the analysis of cosmological data and in the developing of new theoretical models. Already in several, well cited, papers we have investigated the impact of current CMB measurements on dark matter, inflation, reionization, recombination, neutrino physics, variation of fundamental constants, topological defects, dark energy and modified gravity. We are currently involved in two major experimental collaborations: Planck and Euclid with full access to the Planck data and to the most updated specifications for the Euclid satellite. It is important to realize that those dataset are very complex and their handling will require considerable expertise if one wants to squeeze the most out of it. Being already members of these collaborations, and thanks to well established international collaborations, we are in the position to fully exploit these datasets.
In the next few years we will clearly have a substantial improvement in the measurements of the CMB polarization angular power spectra. Indeed, the final data release from the Planck collaboration is expected around the end of 2017. The improved measurement of CMB polarization at large angular scales will be crucial in further determining the abundance of light dark particles as neutrinos or axions. Moreover new observations from ground based experiments as BICEP3, Polarbear and ACTPOL and SPT are expected during 2017 and beginning of 2018. These experiments will measure with unprecendented accuracy the B mode of the CMB polarization produced by weak lensing from cosmic structure and directly connected with the dark matter distribution. These new datasets will not only offer the opportunity of improving current cosmological constraints but will also provide new ways for testing the global scenario by cross correlations with other datasets as galaxy and weak lensing surveys. Indeed new theoretical models have been proposed as TeVeS or emergent gravity where modifications to general relativity can mimic a dark matter component in galaxy rotation curves and velocity dispersion in cluster of galaxies. We plan to test these models with current and future cosmological data.
This large amount of new data and the development of new theories with multiple parameters will obviously lead to the necessity of developing new data analysis codes. Together with new cosmological data analysis methods based on Monte Carlo Markov Chains we plan to develop new codes to better model the theoretical predictions of new dark matter scenarios. Indeed, we plan to create a fruitful bridge between cosmology and particle physics by devising and interpreting the cosmological results under the framework of different dark matter theoretical models.
There is clearly an high potential for possible new discoveries that could have impact not only on cosmology or astrophysics but also on other branches of physics. The possibility of ruling out with cosmological data the inverted neutrino mass hierarchy, for example, will have an enormous impact on neutrino physics and for the several planned or on going beta or double beta decay experiments. An indication for a dark matter annihilation signal in CMB polarization angular spectra will provide a very important complementary confirmation of the Fermi excess at galactic center, interpreted as due to dark matter.
As far as concern gravitational lensing Euclid will give the possibility to measure shear and convergence fields with an unprecedented precision and accuracy. A strong effort on systematics control is crucial to reach this goal. At the same time it is crucial to investigate the potentiality of new tools like flexions and peak statistics to discriminate between different dark energy and dark matter scenarios. All these topics are at the frontier of the present knowledge because until now we hadn't enough high quality data.
Part of this project is also focused on the study of the spectral-spatial anisotropies in the mm-wave sky by means of the Sunyaev-Zeldovich spectrum. It takes advantage of Planck photometric data, and it will help to optimally plan future spectral observations, like with the KISS spectrometer. We will strengthen the effectiveness of galaxy clusters as cosmological probe to constrain dark matter candidates. The merging of high angular resolution of SZ observations, as produced by NIKA2, with lensing observations will allow to constraint cluster total mass radial profiles and their dependence with the dynamical state and hydrostatic equilibrium.