Performance assessment of the gPLUTO code for the numerical modeling of radio galaxy evolution

TL;DR

A detailed performance benchmarking of the recently developed GPU-enabled PLUTO code (gPLUTO), demonstrating runtime speed-ups ranging from an order of magnitude to (approximately) over 30 relative to CPU-only configurations is presented.

Abstract

High-resolution tri-axial simulations are indispensable for realistically co-modeling the dynamical signatures and the radiative fingerprints of astrophysical jets, which are becoming increasingly important in modern computational studies of jet physics. However, such simulations impose extreme computational requirements that often exceed the capabilities of conventional CPU-based codes. GPU-accelerated simulations offer a transformative solution to mitigate these limitations. In this work, we present a detailed performance benchmarking of the recently developed GPU-enabled PLUTO code (gPLUTO), demonstrating runtime speed-ups ranging from an order of magnitude to (approximately) over 30 relative to CPU-only configurations. A direct comparison between computations of extragalactic jet propagation performed at different grid resolutions confirm the physical fidelity and production readiness of the gPLUTO code, while underscoring the importance of resolving the jet radius adequately to capture the jet dynamics accurately. Leveraging GPU-PLUTO's capabilities, we finally present an application by performing high-resolution simulations of giant radio galaxy jets (GRGs $\gtrsim 1$ Mpc), representing the first such well-resolved 3D study to our knowledge (resolving scales down to 500 pc). These simulations probe a range of environmental effects on GRG jets, clarifying their formation from central galaxies within host cosmic structures, rapid peripheral expansion, and the development of asymmetric cocoon morphologies.

Figures (5)

• Figure 1: Sliced representation of the triaxial density profile (mimicked through the triad) of a cosmic galaxy group (with core radii a, b, c, and virial radius $R_{\rm virial}$), representing the ambient medium through which extragalactic jets are injected and propagated in this study. Jets are primarily launched from the center ("GRG_center"), while one case explores injection along the periphery ("GRG_edge"), where the ambient medium is offset by $-\, 600$ kpc. The tilt of the medium relative to the jet propagation axis (along horizontal path) and its triaxiality demonstrate how we can implement symmetry-breaking in the environment to produce more realistic propagation scenarios ("GRG_asymmetry"). White dashed contour lines, labeled inline, highlight the density stratification relevant to understanding jet-medium interactions.
• Figure 2: Comparison of gPLUTO CPU-only and GPU simulations showing the jet length evolution as a function of dynamical age (left) and the evolution of the thermal energy within the jet cocoon as a function of dynamical age (right), highlighting the production readiness of gPLUTO (in GPUs). The plot also illustrates the importance of resolution for accurately capturing jet propagation physics.
• Figure 3: Propagation of a jet reaching giant radio galaxy scales after originating from the center of the large-scale cosmic environment (represented here by a galaxy group, as also inferred by the black density contours). The structure of the jet cocoon is clearly captured using the jet tracer, displayed both as contours (white) and a colormap, and is overplotted on the overall density distribution (all presented in $x-y$ slice at $z = 0$) of the simulated system to illustrate the connection between the jet lobes and the surrounding medium. The evolution time of the simulation is also indicated as inset.
• Figure 4: Similar to Fig. \ref{['fig:GRG_st_centre']}, but in this case the jet is injected from the outskirts of the large-scale cosmic environment, a configuration often associated with giant radio galaxies. The jet propagates rapidly, reaching approximately 700 kpc in just 6.52 Myr. This fast propagation is important for understanding recent observations of giant jets extending to 5 Mpc and beyond, providing insights into their formation and evolution.
• Figure 5: Same as Fig. \ref{['fig:GRG_st_centre']}, but in this case the jet is injected from the center of a triaxial medium to examine its propagation under asymmetric environmental conditions. Unlike the previous giant radio galaxy cases, this jet is bidirectional, allowing us to assess the impact of reduced symmetry on the evolution of the system. The propagation speed is slightly lower here due to the increased environmental resistance of the triaxial structure. The limb-like cocoon feature observed in the jet-base region arises from the backflowing plasma preferentially extending along the steepest pressure gradient. Such a feature is expected to become even more prominent in lower power jets, potentially giving rise to complex morphologies such as X-shaped radio galaxies.