Résumé / Abstract Journal-club_Galaxies

Journal-club Galaxies

« Characterising cosmic filaments using hydrodynamical simulations »

Daniela Galarraga
Inst. Astroph. Spatiale (IAS), Univ. Paris-Sud XI (Orsay, France)

Matter in the Universe is assembled under the action of gravity to form a gigantic network of nodes, filaments, walls, and voids, called the cosmic web. This structure is mainly set by the dynamics of dark matter (DM), which forms the skeleton onto which baryonic (or ordinary) matter is accreted. While the denser cosmic structures (clusters of galaxies) have been thoroughly studied, because of their lower densities and complex morphologies, cosmic filaments and the properties of matter around them are still poorly known. However, these structures are believed to contain almost half of the matter in the Universe. The study of matter at the largest scales is therefore inevitably linked to that of filaments.

I will present a comprehensive study of cosmic filaments today, detected from the galaxy distribution of recent large-scale hydro-dynamical simulations using the DisPerSE code.
The relative radial distribution of DM, gas, and galaxies around filaments is analysed, as well as the temperature and pressure of gas. I will show that filaments of different lengths do not have the same properties, leading to the identification of two extreme populations: the short and long filaments. Short filaments are denser, puffier, and hotter than the long ones. While they trace denser environments in the cosmic web (e.g. close to clusters of galaxies), the long population is often embedded in under-dense regions.
I will show that filaments are essentially made of gas in the warm-hot intergalactic medium (WHIM), their cores are isothermal, and their pressure is ~1000 times lower than values in clusters of galaxies. I will present baryon fraction profiles of these structures, which show that filament cores are baryon depleted and that an excess of gas with respect to the cosmic value is present at the outskirts.
Finally, an estimation of the Sunyaev-Zel'dovich signal of filaments and a comparison with recent observations from Planck data will be shown.

jeudi 4 novembre 2021 - 11:30
Salle des séminaires Évry Schatzman, Institut d'Astrophysique
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