EAGLE (simulation)

EAGLE (simulation)
Name	EAGLE
Developer	Leiden University; Durham University; Max Planck Institute for Astrophysics
Released	2014
Programming language	Fortran, C
Platform	HPC, Supercomputer
License	Proprietary (research)
Genre	Cosmological hydrodynamical simulation

EAGLE (simulation) is a suite of large-scale cosmological hydrodynamical simulations designed to model the formation and evolution of galaxys, black holes, and interstellar medium structures within a Lambda-CDM framework. Developed by a consortium including researchers from Leiden University, Durham University, and the Max Planck Institute for Astrophysics, EAGLE combines N-body gravity solvers with smoothed particle hydrodynamics to reproduce observed properties of galaxy populations across cosmic time. Its aims include matching statistical measures such as the galaxy stellar mass function, Tully–Fisher relation, and galaxy clustering while probing feedback processes from supernovae and active galactic nucleus (AGN) activity.

Overview

EAGLE was conceived to address discrepancies between predictions from pure N-body cold dark matter simulations and observations from surveys like the Sloan Digital Sky Survey, COSMOS, and CANDELS. The project produced multiple volumes with differing resolution and box sizes, enabling comparisons to results from projects such as Millennium, Illustris, and Horizon-AGN. EAGLE emphasizes a physically motivated but computationally efficient treatment of baryonic processes to reproduce emergent properties of spiral galaxys, elliptical galaxys, and dwarf galaxy populations.

Simulation Methodology

EAGLE employs a modified version of the smoothed particle hydrodynamics code used in earlier projects, integrating gravity via a tree-particle mesh scheme similar to that used in GADGET. Initial conditions are generated using transfer functions consistent with Planck cosmological parameters, and perturbations follow the Zel'dovich approximation. The simulations track collisionless dark matter particles and baryonic particles subject to radiative cooling—including metal-line cooling calibrated against yields from Type Ia supernovae and core-collapse supernovae—and heating from a metagalactic ultraviolet/X-ray background modeled after results from the Haardt & Madau synthesis. Star formation follows a pressure-dependent prescription inspired by observed relations in the Kennicutt–Schmidt law parameter space, while black hole seeding and accretion adopt methods benchmarked by studies of quasar demographics and the M–sigma relation.

Subgrid Physics and Calibration

Because key processes occur below the simulation resolution, EAGLE implements subgrid models for stellar feedback, radiative cooling, chemical enrichment, and AGN feedback. Stellar evolution yields and enrichment channels reference nucleosynthetic calculations associated with Woosley & Weaver and Nomoto. AGN feedback is parameterized to capture the effects observed in radio galaxy and Seyfert galaxy populations, with energy injection tuned to reproduce the black hole mass–stellar mass relation. Calibration was performed by matching the low-redshift galaxy stellar mass function, galaxy sizes measured by instruments such as the Hubble Space Telescope, and the specific star formation rate distributions, using observational benchmarks from surveys like GAMA and SDSS. The calibration strategy echoes approaches taken in the OWLS project but differs in prescriptions and tuning targets.

Results and Scientific Findings

EAGLE successfully reproduces several statistical properties of the observed galaxy population, including the galaxy stellar mass function at z~0, the distribution of galaxy sizes, and the bimodality between star-forming and passive systems similar to results from GALEX and WISE photometry. It yields realistic circumgalactic medium properties and metal distributions comparable to absorption-line studies using instruments like Keck Observatory and Very Large Telescope. EAGLE predicts relationships among stellar mass, star-formation rate, and metallicity that align with trends seen in SDSS and high-redshift surveys such as UltraVISTA. The simulation has been used to explore topics including the origins of galactic winds, the impact of AGN on galaxy quenching observed in X-ray and radio studies, and the assembly histories of massive galaxys relevant to results from galaxy cluster observations.

Validation and Comparisons

Comparative studies place EAGLE alongside other contemporary projects—IllustrisTNG, Horizon-AGN, Illustris, Eris, and Millennium-based hydrodynamical extensions—highlighting strengths in reproducing galaxy sizes and stellar mass functions while noting differences in predictions for the low-mass end and circumgalactic medium properties. Validation uses observational datasets from SDSS, GAMA, COSMOS, and high-redshift compilations using Hubble Space Telescope photometry and spectroscopy from VLT instruments. Cross-comparisons also consider dark matter halo statistics from HALO mass function measurements and clustering analyses akin to those in the BOSS survey.

Limitations and Future Development

Despite successes, EAGLE is limited by finite resolution, simplified subgrid models, and uncertainties in chemical yields and feedback efficiencies informed by studies of supernova remnants and AGN energetics. Predicted properties of the lowest-mass dwarf galaxy population and detailed multiphase structure of the interstellar medium remain sensitive to model choices, motivating higher-resolution simulations and alternative hydrodynamics schemes explored in projects like AREPO-based runs. Future development aims to incorporate improved radiation-hydrodynamics treatments, refined black hole physics inspired by observations from Chandra X-ray Observatory and ALMA, and larger suites of simulations to probe environmental effects evident in galaxy cluster studies. These advances will further interface with ongoing observational programs such as Euclid (spacecraft) and the James Webb Space Telescope to test galaxy formation theory.

Category:Cosmological simulations