The cosmology is devoted to the global comprehension of the Universe, such as its geometrical properties, the fundamental particles constituting the matter and energy density and the statistical properties of their distributions, its evolutionary history since the primordial phases of inflationary expansion, about 13.7 Gigayears ago, and its destiny. Such aspects are studied through different astronomical observables: stars, galaxies, clusters of galaxies, and diffuse emission components. The cosmic microwave background (CMB), predicted by the big-bang theory, relic of the hot and dense phase of primordial Universe, is a diffuse and almost isotropic radiation, cooled at T=2.725 Kelvin degrees because of the cosmic expansion. It carries out direct information of the Universe and fundamental physics at only 380000 years after the big-bang, an epoch called of “matter-radiation decoupling” after which cosmic radiation travelled substantially undisturbed up to us, and, undirectly, up to its earliest moments. All the properties of the CMB are object of study at IASFBO. The spectrum is related to the thermodynamical processes in the cosmic plasma; from temperature and polarization anisotropies it is possible to recover parameters, geometry and statistical properties of the Universe; secondary anisotropies take memory of the cosmic structure formation process.

Image of the main phases of the history of the Universe: the dawn of time, the cosmic inflation, the radiation at the decoupling time, and the present structures.

(Credits: NASA/WMAP Science Team)

Perspectives for future cosmic microwave background missions

Design image of the COrE satellite. (Credits: COrE Collaboration).

The accurate and complete study of the cosmic microwave background (CMB) requires further progress.  Very small distortions produced by physical and astrophysical processes ad different cosmic times should be imprinted in the spectrum, substantially of blackbody, of the CMB radiation. They constitute objects for studies of scientific implications and feasibility of future missions.

Great efforts have been dedicated to polarization anisotropies of CMB, in particular for searching the primordial B-mode associated to the stochastic field of gravitational waves, the smoking gun of inflation: its detection means to understand at what energy scale inflation occurred.

The IASFBO contributed, particularly with foreground and theoretical studies, to the proposal of a mission, called  COrE (Cosmic Origins Explorer), for the ESA Cosmic Vision, and it is involved, also on the point of view of new technologies, to improve such researches towards a project in response to future ESA opportunities.

Cosmology statistical analysis

The statistical analysis is a fundamental tool for Cosmology.
The employed methods in the statistical analyses are classified in two categories: the frequentist and the bayesian approach. The former tests a particular cosmological model and computes its probability of validity through a comparison with data. The latter instead starting from the observations, extracts the model that better describes the data.
These analyses imply heavy computations that need the use of supercomputers.

The figure shows an example of how several cosmological data sets are joined together in order to constrain, with a Bayesian approach, two free parameters of the cosmological models, i.e. w (equation of state of the dark energy) = p/rho and Omega_m (dimensionless parameter for the energy density of the matter, baryonic and dark matter).

 Algorithms for observational cosmology

“Cosmology studies the birth and the evolution of the Universe”: This definition suggests either Star Trek or to the Critique of Pure Reason. In real life it is not like that: many times cosmology is just a matter of the “brute force work” and the data analysis sounds much more technical than poetry.

Most of the cosmological data analysis pipeline can be seen as an enormous exercise of lossless compression.
An example: the measurement of the CMB (cosmic microwave background); the Planck satellite will produce 50 terabytes of data, through data analysis, this wealth of information is compressed into about 12 numbers (eg, age, energy budget of the universe, curvature, amount  of dark matter and dark energy). Those few numbers describe parametrically the universe and through them it becomes possible to confirm or reject  the current cosmological theories.

Clearly, in this process it is fundamental the use of parallel computing facilities.
Our institute accesses directly the Italian Inter-university Consortium CINECA as well as the NERSC supercomputing facilities based in California.

Radio-mm-IR astrophysics

Galactic radio emission (dominated by synchrotron) at 1.4 GHz in total intensity and polarization. Note the strong depolarization of the signal in the inner regions. (Credits: C. Burigana et al., 2006, AN, 327 491).

Different astrophysical processes, dominating at specific wavelengths, operate in our Universe. The analysis of radiation from radio to infrared allows us to understand many astrophysical phenomena occurring in galaxies.

Electrons, spiralling in galactic magnetic fields, emit synchrotron radiation, relevant from radio to millimetre, where also free-free emission, associated to the presence of electrons and ionized atoms, diffuse or in localized regions (HII), is also important.

From millimetre to infrared, the thermal emission from interstellar medium dust grains emerges, while rotating dust grains contribute to the millimetre signal, as clearly probed by the Planck satellite, that also discovered thousands of very cold dust cores, at about 10 Kelvin degrees, in our galaxy.

Stars at early and late evolutionary phases, with their envelopes of gas and dust grains, significantly emit in these wavelengths. Furthermore, it is possible that a radiation, produced by the mysterious dark matter, emerges from the inner regions of galaxies. Galaxies aggregate in clusters of galaxies.

The intergalactic space among them if filled by hot gas, achieving temperatures of millions of degrees, that significantly emits in the X-rays but that leaves also well defined signatures in the cosmic microwave background.

Dark Matter,  Dark Energy e Inflazione