David Vallés-Pérez

My primary research interests focus on the assembly of galaxy clusters, with a special focus on the dynamics of the turbulent and magnetised intracluster medium (ICM). This involves developing and analysing large cosmological simulations to study, amongst other things, the accretion history of galaxy clusters, the properties of the gas that is accreted onto them, and the impact of this accretion on the internal properties of the cluster.

Besides galaxy clusters, I am currently or have been closely involved in the study of other astrophysical systems and scenarios, always within the frame of computational astrophysics. These include the study of cosmic voids, the assembly of galaxies and their interaction with the ICM, or the propagation of relativistic, magnetised jets.

More generally, I am interested in any astrophysical application of (magneto)-hydrodynamics and computational astrophysics, with a strong focus on the development of new algorithms and tools to enable them and their analysis.

~ Research lines ~

Development of analysis tools for hydrodynamical and cosmological simulations

I am the main developer of several tools for the analysis of hydrodynamical and/or cosmological simulations, including:

vortex: a code to perform a Helmholtz (compressive + solenoidal) and a Reynolds (bulk + turbulent) decomposition of the velocity field of patch-based AMR simulations with a method based on the resolution of elliptic PDEs. [GitHub]
vortex-p: same purpose as vortex, but for particle-based (or, in general, any unstructured input data) simulations. [GitHub] [docs]
ASOHF: a spherical-overdensity halo finder for N-Body simulations, capable of dealing with substructures using a multi-scale density field interpolation, as well as characterising galaxies within DM haloes, and building merger trees, amongst other things. [GitHub] [docs]

Additionally, I have contributed to the development of the AMR hydro+N-Body code MASCLET, and am the main developer of the masclet_framework Python library for the analysis of its outputs.

Selected publications: 2, 5, 9.

Galaxy cluster assembly

I am interested in the assembly of galaxy clusters, both from the perspective of their dark matter halo, and especially with respect to the (thermo)dynamics of the intracluster medium (ICM). This comprises the study of the accretion history of galaxy clusters (including the different ways to quantify it), the properties of the gas that is accreted onto them, and the impact of this accretion on the internal properties of the cluster.

So far, I have worked on the determination and comparison of several proxies for the accretion rates, on the study of the spatial distribution of accretion flows, and on the characterisation of the dynamical/assembly state of group- and cluster-sized dark matter haloes using properties at a given redshift.

Selected publications: 1, 6, 7.

Turbulence in galaxy clusters

Turbulence is a pervasive phenomenon in astrophysical flows, and a key ingredient in the dynamics of the ICM. Using vortex, I have studied the properties, the generation and the distribution of compressive and solenoidal turbulence in galaxy clusters in connection to their assembly history.

I am also interested in the impact of the numerical scheme used to solve the equations of hydrodynamics (grid vs. particle codes, impact of AMR and reconstruction methods in Eulerian codes, effect of resolution, etc.), and on the impact of turbulence on the observable properties of clusters.

Selected publications: 2, 3, 9.

Shocks in galaxy clusters

Shocks are another ubiquitous feature of cosmological baryonic flows. In galaxy clusters, they are responsible for the heating of the ICM, the acceleration of charged particles, or the generation of turbulence. I am interested in the properties of both, external and internal shocks, their impact on ICM properties, and their connection to observation signatures (e.g., diffuse radio emission).

I have studied the main properties of the very strong outermost accretion shocks of galaxy clusters and groups, finding that they appear to follow a scaling relation linking the total mass in large apertures, the shock Mach number, and the shock radius. (Selected publication: 8).

Amplification of magnetic fields in galaxy clusters

Micro-Gauss level turbulent magnetic fields fill the ICM and shape its radio emission, but their precise origin and amplification mechanisms are not yet fully understood.

Being clearly related to the turbulent dynamics of the intracluster plasma, I am interested in the study of the amplification of magnetic fields in galaxy clusters, and their connection to the turbulent properties of the ICM. This includes the study of the properties of the magnetic field, the generation of magnetic fields in the ICM, and the impact of magnetic fields on the observable properties of galaxy clusters.

(Quilis et al. 2020)

Dynamics of cosmic voids & void galaxies

Cosmic voids, within a cosmological context, become complex entities themselves, hosting substructure in the form of haloes, tenuous filaments, and subvoids themselves. I am interested in the dynamics of these structures, their interaction with the cosmic web, and the properties of galaxies that inhabit them.

Looking at the properties of cosmic voids extracted from the density field of cosmological simulations, I have found the interesting result that their velocity field is not always purely outflowing, but voids can instead host significant, long-lived inflows. Part of these inflows coming from denser regions, this could have important implications for the assembly of void galaxies. (Selected publication: 4).