Dark galaxies: Probing the ΛCDM cosmological model on unprecedented scales

Description du projet

Faire la lumière sur la matière noire et la formation des galaxies naines

Le modèle ΛCDM (Lambda Cold Dark Matter) représente la dernière incarnation de notre compréhension du cosmos, qui postule que notre Univers est essentiellement composé de matière noire. Il donne également une description raisonnable de l’abondance, de la structure et de l’agglomération des halos de matière noire, les régions à partir desquelles naissent les galaxies. Malgré son succès, on ignore si ce modèle peut décrire avec précision la formation des galaxies naines. Le projet DarkGalaxies, financé par l’UE, sondera le modèle ΛCDM à des échelles exceptionnellement petites, en se fondant sur une prédiction fondamentale du modèle: l’existence de galaxies noires proches. Les résultats du projet pourraient enrichir nos connaissances sur la nature de la matière noire et la formation des structures à de petites échelles cosmiques.

Objectif

The currently favoured Lambda-Cold-Dark-Matter (ΛCDM) cosmological model makes specific predictions about the
abundance, structure and clustering of dark matter halos (DMHs), the sites where galaxies form. These predictions are
accurate at describing large scale observations. On smaller scales, the agreement between ΛCDM and observations of
dwarf galaxies is unclear because (i) the structure of DMHs depends on particularities of different galaxy formation models,
and (ii) observations of dwarfs suffer from sizable uncertainties. Is ΛCDM successful on small scales? A definite answer to
this major open question may either reveal the nature of DM or change dramatically our understanding of structure formation
in the Universe. My research will deliver the foundations to probe ΛCDM on unprecedented small scales by exploiting a
fundamental prediction of the model: the existence of nearby DM-dominated “dark” galaxies (so-called RELHICs). RELHICs
are pristine collapsed DMHs that contain sufficient gas leftover from the epoch of reionization to recombine and emit
radiation that can be observed in 21 cm (or recombination lines) but without becoming self-shielding and forming stars.

Firstly, I will develop and analyse high-resolution hydrodynamical simulations performed with state-of-the-art numerical
codes that include cutting-edge galaxy formation and radiative-transfer (RT) models to predict the abundance and clustering
of RELHICs. Secondly, I will design robust survey strategies targeted at detecting RELHICs with current and upcoming
observing facilities (e.g. ALMA, FAST, MEERKAT, WALLABY). The detection and characterization of REHICs will offer an
unprecedented and clean probe to ΛCDM on scales that have not yet been probed.

My extensive expertise in numerical simulations, cosmology and galaxy formation, combined with that of Prof. Michele
Fumagalli in RT and physics of the interstellar medium will enable me to materialize my predictions into observational probes.