The enrichment of the intergalactic medium with adiabatic feedback – I. Metal cooling and metal diffusion

By S. Shen, James Wadsley, G. Stinson. 2009

325 citations recorded by the source corpus.

A study of metal enrichment of the intergalactic medium (IGM) using a series of smooth particle hydrodynamics (SPH) simulations is presented, employing models for metal cooling and the turbulent diffusion of metals and thermal energy. An adiabatic feedback mechanism was adopted where gas cooling was prevented on the timescale of supernova bubble expansion to generate galactic winds without explicit wind particles. The simulations produced a cosmic star formation history (SFH) that is broadly consistent with observations until z � 0.5, and a steady evolution of the universal neutral hydrogen fraction (HI) that compares reasonably well with observations. The evolution of the mass and metallicities in stars and various gas phases was investigated. At z=0, about 40% of the baryons are in the warm-hot intergalactic medium (WHIM), but most metals (80%-90%) are locked in stars. At higher redshifts the proportion of metals in the IGM is higher due to more efficient loss from galaxies. The r also indicate that IGM metals primarily reside in the WHIM throughout cosmic history, which differs from simulations with hydrodynamically decoupled explicit winds. The metallicity of the WHIM lies between 0.01 and 0.1 solar with a slight decrease at lower redshifts. The metallicity evolution of the gas inside galaxies are broadly consistent with observations, but the diffuse IGM is under enriched at z � 2.5. Galactic winds most efficiently enrich the IGM for halos in the intermediate mass range 10 10 M � - 10 11 M � . At the low mass end gas is prevented from accreting onto halos and has very low metallicities. At the high mass end, the fraction of halo baryons escaped as winds declines along with the decline of stellar mass fraction of the galaxies. This is likely because of the decrease in star formation activity and decrease in wind escape efficiency. Metals enhance cooling which allows WHIM gas to cool onto galaxies and increases star formation. Metal diffusion allows winds to mix prior to escape, decreasing the IGM metal content in favour of gas within galactic halos and star forming gas. Diffusion significantly increases the amount of gas with low metallicities and changes the density-metallicity relation.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5b762ff94920df4dae49b876c9c58dfd2302e3b5

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Citations in the corpus

THE METALLICITY EVOLUTION OF INTERACTING GALAXIES (2011, methodology): “Such methods have been shown to be important for tracking metallicity in cosmological simulations (e.g., Shen et al. 2010) and we intend to assess their influence in isolated and merging galactic systems.”
Metallicity gradients in disks - Do galaxies form inside-out? (2012, methodology): “…radiation field (Haardt & Madau 1996) is employed, and cooling is derived from the contributions of both primordial gas and metals; the metal cooling grid is derived using CLOUDY (v.07.02: Ferland et al. (1998)), under the assumption of ionisation of equilibrium, as detailed by Shen et al. (2010).”
NIHAO - XI. Formation of ultra-diffuse galaxies by outflows (2016, unknown): “The code includes a subgrid model for turbulent mixing of metals and energy (Wadsley et al. 2008), ultraviolet heating, ionization and metal cooling (Shen et al. 2010).”
NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time (2015, background): “The code includes a subgrid model for turbulent mixing of metals and energy (Wadsley et al. 2008), heating and cooling include photoelectric heating of dust grains, ultraviolet (UV) heating and ionization and cooling due to hydrogen, helium and metals (Shen et al. 2010).”
The EAGLE project: Simulating the evolution and assembly of galaxies and their environments (2014, methodology): “The implementation of diffusion can be used to increase the mixing (e.g. Greif et al. 2009; Shen et al. 2010), but we have opted not to do this because the effective diffusion coefficients that are appropriate for the ISM and IGM remain unknown.”
HALO EXPANSION IN COSMOLOGICAL HYDRO SIMULATIONS: TOWARD A BARYONIC SOLUTION OF THE CUSP/CORE PROBLEM IN MASSIVE SPIRALS (2011, methodology): “…high resolution cosmological hydrodynamic simulation of a massive spiral galaxy that includes cooling due to hydrogen and heavier "metal" elements (Shen et al. 2010), UV background radiation (Haardt & Madau from CLOUDY), a simple commonly used star formation prescription, adiabatic supernova…”
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies (2012, background): “As a significant improvement over most cosmological simulations carried to the present time these new simulations include both metal lines and H2 cooling (Shen et al. 2010, CH11).”
The Romulus cosmological simulations: a physical approach to the formation, dynamics and accretion models of SMBHs (2016, methodology): “The SPH implementation includes thermal diffusion (Shen et al. 2010) and eliminates artificial gas surface tension through the use of a geometric mean density in the SPH force expression (Ritchie & Thomas 2001; Menon et al. 2015; Governato et al. 2015).”
The structure and dynamical evolution of the stellar disc of a simulated Milky Way-mass galaxy (2016, background): “We have explicitly checked that including subresolution metal diffusion in our simulation (as in Shen et al. 2010) does not dramatically reduce the scatter.”
INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS (2013, result): “Our results are less directly comparable to observations than chemistrybased investigations, but the age cohorts are physically simpler than chemically-selected tracer populations and avoid the uncertainties associated with numerical chemical enrichment implementation (e.g., Shen et al. 2010).”
Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback (2012, methodology): “…photoionization and heating from the Haardt & Madau (2005) UV background, Compton cooling, and hydrogen, helium and metal cooling from 10 to 109 K. Shen et al. (2010) showed that T > 104 K metal cooling including the photoionization effects of the UV background reduces cooling by an order of…”
A BUDGET AND ACCOUNTING OF METALS AT z ∼ 0: RESULTS FROM THE COS-HALOS SURVEY (2013, background): “…appear necessary to reach the level of observed CGM and intergalactic medium (IGM) metal enrichment (Oppenheimer & Davé 2006; Scannapieco et al. 2006; Shen et al. 2010, 2012; Booth et al. 2012; Oppenheimer et al. 2012; Stinson et al. 2012; Ford et al. 2013; Crain et al. 2013; Berry et al. 2013).”
Gasoline2: a modern smoothed particle hydrodynamics code (2017, methodology): “Sub-grid turbulence may be modelled in SPH using the trace-free local shear tensor, S (Wadsley et al. 2008; Shen et al. 2010).”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “Shen et al. (2010) describes the primordial and metal-line cooling used, as well as the diffusion of metals that captures the effect of the turbulent interstellar medium on metal mixing.”
REPRODUCING THE STELLAR MASS/HALO MASS RELATION IN SIMULATED ΛCDM GALAXIES: THEORY VERSUS OBSERVATIONAL ESTIMATES (2012, methodology): “The simulations include a scheme for turbulent mixing that redistributes heavy elements among gas particles (Shen et al. 2010).”
A new class of accurate, mesh-free hydrodynamic simulation methods (2014, background): “And we set the global constant αC to a relatively conservative value αC ≈ 0.25; together with the limiters in the equation this leads to greatly reduced diffusion compared to some prescriptions for conductivity in the literature (e.g. Shen et al. 2010). c© 0000 RAS, MNRAS 000, 000–000”