Properties of the diffuse gas component in filaments detected in the Dianoga cosmological simulations

¹ Faculty of Mathematics and Physics, University of Ljubljana, Jadranska cesta 19, 1000 Ljubljana, Slovenia
² INAF – Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
³ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34014 Trieste, Italy
⁴ Department of Physics, Astronomy Section, University of Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
⁵ INFN, Instituto Nazionale di Fisica Nucleare, Via Valerio 2, 34127 Trieste, Italy
⁶ ICSC – Italian Research Center on High Performance Computing, Big Data and Quantum Computing, via Magnanelli 2, 40033, Casalecchio di Reno, Italy
⁷ Universitäts-Sternwarte, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.1, 81679 München, Germany
⁸ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany

Received: 22 March 2024
Accepted: 27 July 2024

Abstract

Context. Cosmic filaments are observationally hard to detect. However, hydrodynamical cosmological simulations are ideal laboratories where the evolution of the cosmic web can be studied, and they allow for easier insight into the nature of the filaments.

Aims. We investigate how the intrinsic properties of filaments are evolving in areas extracted from a larger cosmological simulation. We aim to identify significant trends in the properties of the warm-hot intergalactic medium (WHIM) and suggest possible explanations.

Methods. To study the filaments and their contents, we selected a subset of regions from the Dianoga simulation. We analysed these regions that were simulated with different baryon physics, namely with and without AGN feedback. We constructed the cosmic web using the subspace constrained mean shift (SCMS) algorithm and the sequential chain algorithm for resolving filaments (SCARF). We examined the basic physical properties of filaments (length, shape, mass, radius) and analysed different gas phases (hot, WHIM, and colder gas components) within those structures. The evolution of the global filament properties and the properties of the gas phases were studied in the redshift range 0 < z < 1.48.

Results. Within our simulations, the detected filaments have, on average, lengths below 9 Mpc. The filaments’ shape correlates with their length, as the longer they are, the more likely they are curved. We find that the scaling relation between mass M and length L of the filaments is well described by the power law M ∞ L^1.7. The radial density profile widens with redshift, meaning that the radius of the filaments becomes larger over time. The fraction of gas mass in the WHIM phase does not depend on the model and rises towards lower redshifts. However, the included baryon physics has a strong impact on the metallicity of gas in filaments, indicating that the AGN feedback impacts the metal content already at redshifts of z ~ 2.