arXiv subjects

Federico A. Stasyszyn

Publications and source records attributed to Federico A. Stasyszyn.

12 recordsLinked to original sources

arXiv2026

Smoothed particle magnetohydrodynamics for simulations of galaxy and cosmic structure formation

We introduce a novel formulation of cosmological smoothed particle magnetohydrodynamics (SPMHD), designed to model magnetic field physics in a vast array of nonlinear astrophysical systems, and which we have implemented in the highly-parallel, entirely modular, and open-source simulation code SWIFT. Our numerical scheme is designed to offer optimal performance at a minimal computational cost, keep a low memory footprint, and most notably couple robustly to effective sub-resolution recipes of galaxy formation. This is achieved through expressing our evolution equations in a density-energy conservative form, and augmenting them with discontinuity-capturing terms tailored to high dynamic range simulations, which are further modulated by adaptive switches that drastically improve coupling to sub-grid models and limit spurious dissipation. We moreover present novel suggestions for the two major regularisation techniques used in modern SPMHD, namely a tensile instability correction and mixed hyperbolic/parabolic divergence-cleaning scheme, to ensure code stability in highly dynamical scenarios. We evaluate the performance of our method on a series of problems of increasing complexity, culminating in three astrophysical applications which have historically proven challenging for mesh-less methods: we study jet launching from a forming proto-stellar core, dynamo amplification in a massive galaxy cluster and magnetic field evolution in a Milky Way-like disk galaxy; the latter constitutes the first reported coupling of the EAGLE galaxy formation model to a magnetohydrodynamics solver. Keeping model hyperparameters fixed across our test suite to provide a transparent picture of our method's capabilities in production, we demonstrate sound performance and convergence with resolution on standard `laboratory' numerical experiments, as well as competitive capabilities in realistic applications.

astro-ph.GA↗

arXiv2025

Kinematic dynamos and resolution limits for Smoothed Particle Magnetohydrodynamics

Understanding the origin and evolution of magnetic fields on cosmological scales opens up a window into the physics of the early Universe. Numerical simulations of such fields require a careful treatment to faithfully solve the equations of magnetohydrodynamics (MHD) without introducing numerical artefacts. In this paper, we study the growth of the magnetic fields in controlled kinematic dynamo setups using both smoothed particle hydrodynamics implementations in the SWIFT code. We assess the quality of the reconstructed solution in the Roberts flow case against the reference implementation in the Pencil code and find generally a good agreement. Similarly, we reproduce the known features of the more complex ABC flow. Using a simple induction-diffusion balance model to analyse the results, we construct an "overwinding" trigger metric to locally detect regions where the magnetic diffusion cannot counteract the expected induction because of limitations in the method's ability to resolve magnetic field gradients. This metric is then used to identify the necessary resolution and resistivity levels to counteract the overwinding problem. We finally apply this metric to adiabatic cosmological simulations and discuss the resolution requirements needed to resolve the growth of the primordial fields without artefacts.

astro-ph.CO↗

arXiv2025

Traces of the evolution of cosmic void galaxies: An Integral Field Spectroscopy based analysis

Galaxies in the most underdense regions of the Universe, known as cosmic voids, exhibit astrophysical properties that suggest a distinct evolutionary path compared to galaxies in denser environments. Numerical simulations indicate that the assembly of void galaxies occurs later, leading to galaxies with younger stellar populations, low metallicities, and a high gas content in their halos, which provides the fuel to sustain elevated star formation activity. Our objective in this work is to test these numerical predictions with observational data by comparing galaxies in voids with galaxies in non-void environments. We used voids identified in SDSS data and galaxies from the MaNGA survey, which provides galaxies with integral field spectroscopy (IFS). We separated the galaxies into void and non-void samples, mimicked the magnitude distribution, and compared their integrated astrophysical properties as well as the metallicity and age profiles through a stacking technique, ETGs and LTGs separately. We find that void galaxies have younger and less metal-rich stellar populations. Regarding gas mass, we do not find differences across environments. When dividing galaxies into ETGs and LTGs, we observe that ETGs show negative gradients in both age and metallicity, with void galaxies consistently appearing younger and less metal-rich. For LTGs, age gradients are also negative, showing younger populations in void galaxies. However, we do not find statistically significant differences in stellar metallicity gradients between void and non-void environments. Our results show how the astrophysical properties of galaxies in voids differ from those of galaxies in the rest of the Universe. This suggests that the void environment plays a role in the evolution of its galaxies, delaying their assembly and growth.

astro-ph.GA↗

arXiv2023

Magnetic Fields in Cosmic Voids

Magnetic fields are one of most concealed components of the universe. They are observed as part of the intergalactic medium and on galaxy cluster scales, however their origin and evolution is unclear. In this work we use the IllustrisTNG simulation to investigate the effects of magnetic fields in cosmic voids, the least dense regions of the universe. We find that, under the hypothesis of a uniform primordial magnetic field, the voids still reflect the primordial properties of the fields. On the other hand, the galaxies in their interior acquire weaker magnetic fields than galaxies in denser environments.

astro-ph.GA↗

arXiv2023

Local and large-scale effects on the astrophysics of void-galaxies

Galaxies in cosmic voids have been reported with properties related to a delayed evolution with respect to the Universe in general. These characteristics reflect the interaction of galaxies with the environment. However, it is not clear the degree of influence of the large-scale structure on the properties of void galaxies or, if these are only influenced by the low local density around them typical of these regions. In this article we identified cosmic voids in the SDSS-DR16 and studied various properties of galaxies, such as g-r colour, star formation rate, and concentration. To characterise the local environment, we have identified groups of galaxies and studied their properties as a function of their dark matter and stellar masses, analysing separately those found in voids and in the general sample. Our results show that galaxies that inhabit haloes of a given mass (below \sim 10^13.5 M_\dot ), are bluer, have a higher star formation rate and are less concentrated when the host halo is inside voids compared to other regions. For larger halo masses, the trend disappears. We also analyse whether the properties of galaxies are sensitive to the type of voids that inhabit. This is done by separating voids embedded in overdense regions (S-type) from those that asymptotically converge to the average density of the universe (R-type). We found that galaxies in R-type voids are bluer, with higher SFR and less concentration than in S-type voids. Our results indicate some degree of correlation of galaxy properties with the large-scale environment provided by voids, suggesting possible second-order mechanisms in galaxy evolution.

astro-ph.GA↗

arXiv2022

Imprints of the cosmic void evolution on the baryon processes inside galaxy haloes

Cosmic voids provide a unique environment to study galaxy formation and evolution. In this paper, we analyse a set of hydrodynamic zoom-in simulations of voids, to analyse in detail their inner structures. These voids were identified in a cosmological simulation and classified according to their surrounding dynamics at very large scales: whether they are in expansion or contraction at their outskirts. We study how these environments and the dynamics of voids impact the baryonic processes inside haloes and their mechanisms of formation and evolution. We find an under-abundance of processed gas within the voids that can be associated with the lack of massive haloes. By studying the dynamical phase-space diagram of haloes and the halo-particle correlation function, we find that haloes inside of contracting voids are slightly affected by the presence of bigger structures, in comparison to haloes in the inner regions of expanding voids. Consistent signals are obtained both when using dark matter and gas particles. We show that the halo assembly depends on the void dynamical state: haloes in expanding voids assemble slowly than those in contracting voids and in the general universe. This difference in the assembly impacts the baryonic evolution of haloes. Overall the redshift range analysed, haloes in voids have less baryon content than haloes in the general universe and particularly at z = 0 less stellar content. Our results suggest that the large scale void environment modulate the baryonic process occurring inside haloes according to the void dynamical state.

astro-ph.CO↗

arXiv2021

Ill-posedness of the mean-field dynamo equations with a linear electromotive force

We show that the initial-value problem for the non-relativistic magnetic dynamo equation turns out to be ill-posed when the electromotive force depends linearly on the magnetic field. This result implies that the increasing of magnetic energy does not necessarily come from physical amplification mechanisms, since certain magnetic modes could arbitrarily grow as wave-frequency increases, despite any dynamo-like process. Thus, up to this order, the theory is not suitable for astrophysical simulations. We then study the case when electromotive forces are linear in magnetic field derivatives, showing that the resulting system has a well-posed problem. Finally, we apply the well-posed theory to the force-free regime, for which we find bounds for the corresponding magnetic energy analyzing the evolution of the magnetic helicity.

astro-ph.HE↗

arXiv2021

Magnetic field generation from primordial black hole distributions

We introduce a statistical method for estimating magnetic field fluctuations generated from primordial black hole (PBH) populations. To that end, we consider monochromatic and extended Press-Schechter PBH mass functions, such that each constituent is capable of producing its own magnetic field due to some given physical mechanism. Assuming linear correlation between magnetic field fluctuations and matter over-densities, our estimates depend on the mass function, the physical field generation mechanism by each PBH constituent, and the characteristic PBH separation. After computing the power spectrum of magnetic field fluctuations, we apply our formalism to study the plausibility that two particular field generation mechanisms could have given rise to the expected seed fields according to current observational constraints. The first mechanism is the Biermann battery and the second one is due to the accretion of magnetic monopoles at PBH formation, constituting magnetic PBHs. Our results show that, for monochromatic distributions, it does not seem to be possible to generate sufficiently intense seed fields in any of the two field generation mechanisms. For extended distributions, it is also not possible to generate the required seed field by only assuming a Biermann battery mechanism. In fact, we report an average seed field by this mechanism of about 10^{-47} G, at z = 20. For the case of magnetic monopoles we instead assume that the seed values from the literature are achieved and calculate the necessary number density of monopoles. In this case we obtain values that are below the upper limits from current constraints.

astro-ph.CO↗

arXiv2020

Detection and analysis of cluster-cluster filaments

In this work, we identify and analyse the properties of cluster-cluster filaments within a cosmological simulation assuming that they are structures connecting maxima of the density field defined by dark matter halos with masses $M \, \ge 10^{14}\, h^{-1} \mathrm{M_{\odot}}$. To extract these filaments we develop an identification algorithm based on two standard tools: the Minimal Spanning Tree (MST) and the Friends of Friends (FoF) algorithm. Focusing our analysis on the densest dark matter filaments, we found that the radial density profile, at scales around $1\, h^{-1} \mathrm{Mpc}$, approximately follow a power-law function with index -2. Without making any assumption about the velocity field, our algorithm finds that the saddle point arises as a natural characteristic of the filamentary structure. In addition, its location along the filament depends on the masses of the halos at the filament ends. We also found that the infall velocities follow a cross-pattern near the saddle point, being perpendicular to the filament spine when approaching from low-density regions, and parallel away from the saddle point towards the ends of the filament. Following theoretical prescriptions, we estimate the linear density from the transverse velocity dispersion, finding a good correspondence with the measured mass per unit length of our filaments. Our results can be applied to observational samples of filaments in order to link the saddle point location and the mass per unit length with measurements obtained from observations such as cluster masses and the velocity dispersion of galaxies.

astro-ph.CO↗

arXiv2019

Faraday Rotation Measure Dependence on Galaxy Clusters Dynamics

We study the magnetic fields in galaxy clusters through Faraday rotation measurements crossing systems in different dynamical states. We confirm that magnetic fields are present in those systems and analyze the difference between relaxed and unrelaxed samples with respect to the dispersion between their inherent Faraday Rotation measurements. We found an increase of this RM dispersion and a higher RM overlapping frequency for unrelaxed clusters. This fact suggests that a large scale physical process is involved in the nature of unrelaxed systems and possible depolarization effects are present in the relaxed ones. We show that dynamically unrelaxed systems can enhance magnetic fields to large coherence lengths. In contrast, the results for relaxed systems suggests that small-scale dynamo can be a dominant mechanism for sustaining magnetic fields, leading to intrinsic depolarization.

astro-ph.CO↗

arXiv2012

On the magnetic fields in voids

We study the possible magnetization of cosmic voids by void galaxies. Recently, observations revealed isolated starforming galaxies within the voids. Furthermore, a major fraction of a voids volume is expected to be filled with magnetic fields of a minimum strength of about $10^{-15}$ G on Mpc scales. We estimate the transport of magnetic energy by cosmic rays (CR) from the void galaxies into the voids. We assume that CRs and winds are able to leave small isolated void galaxies shortly after they assembled, and then propagate within the voids. For a typical void, we estimate the magnetic field strength and volume filling factor depending on its void galaxy population and possible contributions of strong active galactic nuclei (AGN) which border the voids. We argue that the lower limit on the void magnetic field can be recovered, if a small fraction of the magnetic energy contained in the void galaxies or void bordering AGNs is distributed within the voids.

astro-ph.CO↗

arXiv2012

Origin of strong magnetic fields in Milky-Way like galactic haloes

An analytical model predicting the growth rates, the absolute growth times and the saturation values of the magnetic field strength within galactic haloes is presented. The analytical results are compared to cosmological MHD simulations of Milky-Way like galactic halo formation performed with the N-body / \textsc{Spmhd} code \textsc{Gadget}. The halo has a mass of $\approx{}3\cdot{}10^{12}$ $M_{\odot}$ and a virial radius of $\approx{}$270 kpc. The simulations in a $Λ$CDM cosmology also include radiative cooling, star formation, supernova feedback and the description of non-ideal MHD. A primordial magnetic seed field ranging from $10^{-10}$ to $10^{-34}$ G in strength agglomerates together with the gas within filaments and protohaloes. There, it is amplified within a couple of hundred million years up to equipartition with the corresponding turbulent energy. The magnetic field strength increases by turbulent small-scale dynamo action. The turbulence is generated by the gravitational collapse and by supernova feedback. Subsequently, a series of halo mergers leads to shock waves and amplification processes magnetizing the surrounding gas within a few billion years. At first, the magnetic energy grows on small scales and then self-organizes to larger scales. Magnetic field strengths of $\approx{}10^{-6}$ G are reached in the center of the halo and drop to $\approx{}10^{-9}$ G in the IGM. Analyzing the saturation levels and growth rates, the model is able to describe the process of magnetic amplification notably well and confirms the results of the simulations.

astro-ph.CO↗