TY - JOUR
T1 - ATOMIC CHEMISTRY in TURBULENT ASTROPHYSICAL MEDIA. II. EFFECT of the REDSHIFT ZERO METAGALACTIC BACKGROUND
AU - Gray, William J.
AU - Scannapieco, Evan
N1 - Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.
PY - 2016/2/20
Y1 - 2016/2/20
N2 - We carry out direct numerical simulations of turbulent astrophysical media exposed to the redshift zero metagalactic background. The simulations assume solar composition and explicitly track ionizations, recombinations, and ion-by-ion radiative cooling for hydrogen, helium, carbon, nitrogen, oxygen, neon, sodium, magnesium, silicon, sulfur, calcium, and iron. Each run reaches a global steady state that depends not only on the ionization parameter, U, and mass-weighted average temperature, TMW, but also on the one-dimensional turbulent velocity dispersion, σ1D. We carry out runs that span a grid of models with U ranging from 0 to 10-1 and σ1D ranging from 3.5 to 58 km s-1, and we vary the product of the mean density and the driving scale of the turbulence, nL, which determines the average temperature of the medium, from nL = 1016 to nL = 1020 cm-2. The turbulent Mach numbers of our simulations vary from M ≈ 0.5 for the lowest velocity dispersion cases to M ≈ 20 for the largest velocity dispersion cases. When M ≲ 1, turbulent effects are minimal, and the species abundances are reasonably described as those of a uniform photoionized medium at a fixed temperature. On the other hand, when M ≳ 1, dynamical simulations such as the ones carried out here are required to accurately predict the species abundances. We gather our results into a set of tables to allow future redshift zero studies of the intergalactic medium to account for turbulent effects.
AB - We carry out direct numerical simulations of turbulent astrophysical media exposed to the redshift zero metagalactic background. The simulations assume solar composition and explicitly track ionizations, recombinations, and ion-by-ion radiative cooling for hydrogen, helium, carbon, nitrogen, oxygen, neon, sodium, magnesium, silicon, sulfur, calcium, and iron. Each run reaches a global steady state that depends not only on the ionization parameter, U, and mass-weighted average temperature, TMW, but also on the one-dimensional turbulent velocity dispersion, σ1D. We carry out runs that span a grid of models with U ranging from 0 to 10-1 and σ1D ranging from 3.5 to 58 km s-1, and we vary the product of the mean density and the driving scale of the turbulence, nL, which determines the average temperature of the medium, from nL = 1016 to nL = 1020 cm-2. The turbulent Mach numbers of our simulations vary from M ≈ 0.5 for the lowest velocity dispersion cases to M ≈ 20 for the largest velocity dispersion cases. When M ≲ 1, turbulent effects are minimal, and the species abundances are reasonably described as those of a uniform photoionized medium at a fixed temperature. On the other hand, when M ≳ 1, dynamical simulations such as the ones carried out here are required to accurately predict the species abundances. We gather our results into a set of tables to allow future redshift zero studies of the intergalactic medium to account for turbulent effects.
KW - ISM: abundances
KW - ISM: atoms
KW - astrochemistry
KW - turbulence
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U2 - 10.3847/0004-637X/818/2/198
DO - 10.3847/0004-637X/818/2/198
M3 - Article
AN - SCOPUS:84960153328
SN - 0004-637X
VL - 818
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 198
ER -