TY - JOUR
T1 - Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations
AU - Kim, Jeong Gyu
AU - Gong, Munan
AU - Kim, Chang Goo
AU - Ostriker, Eve C.
N1 - Funding Information:
We are grateful to the referee for a careful reading of the manuscript and critical comments for its improvement. We thank Shmuel Bialy and Mark Wolfire for sharing their data and Bruce Draine, Taysun Kimm, and Aaron Smith for helpful discussions. J.-G.K. acknowledges support from the Lyman Spitzer Jr. Postdoctoral Fellowship at Princeton University and from the EACOA Fellowship awarded by the East Asia Core Observatories Association. M.G. acknowledges support from Paola Caselli and the Max Planck Institute for Extraterrestrial Physics. J.-G.K. and M.G. acknowledge the Paris-Saclay University’s Institut Pascal program “The Self-Organized Star Formation Process” and the Interstellar Institute for hosting discussions that nourished the development of the ideas behind this work. This work was supported in part by NASA ATP grant No. NNX17AG26G, NSF grant No. AST-1713949, and grant No. 510940 from the Simons Foundation to E. C. Ostriker.
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2023/1/1
Y1 - 2023/1/1
N2 - We present an efficient heating/cooling method coupled with chemistry and UV radiative transfer that can be applied to numerical simulations of the interstellar medium (ISM). We follow the time-dependent evolution of hydrogen species (H2, H, H+), assume carbon/oxygen species (C, C+, CO, O, and O+) are in formation-destruction balance given the nonsteady hydrogen abundances, and include essential heating/cooling processes needed to capture the thermodynamics of all ISM phases. UV radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for H2 self-shielding; cosmic-ray heating and ionization are also included. To validate our methods and demonstrate their application for a range of density, metallicity, and radiation fields, we conduct a series of tests, including the equilibrium curves of thermal pressure versus density, the chemical and thermal structure in photodissociation regions, H i-to-H2 transitions, and the expansion of H ii regions and radiative supernova remnants. Careful treatment of photochemistry and cosmic-ray ionization is essential for many aspects of ISM physics, including identifying the thermal pressure at which cold and warm neutral phases coexist. We caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ISM. Our new model is implemented in the MHD code Athena and incorporated in the TIGRESS simulation framework, for use in studying the star-forming ISM in a wide range of environments.
AB - We present an efficient heating/cooling method coupled with chemistry and UV radiative transfer that can be applied to numerical simulations of the interstellar medium (ISM). We follow the time-dependent evolution of hydrogen species (H2, H, H+), assume carbon/oxygen species (C, C+, CO, O, and O+) are in formation-destruction balance given the nonsteady hydrogen abundances, and include essential heating/cooling processes needed to capture the thermodynamics of all ISM phases. UV radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for H2 self-shielding; cosmic-ray heating and ionization are also included. To validate our methods and demonstrate their application for a range of density, metallicity, and radiation fields, we conduct a series of tests, including the equilibrium curves of thermal pressure versus density, the chemical and thermal structure in photodissociation regions, H i-to-H2 transitions, and the expansion of H ii regions and radiative supernova remnants. Careful treatment of photochemistry and cosmic-ray ionization is essential for many aspects of ISM physics, including identifying the thermal pressure at which cold and warm neutral phases coexist. We caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ISM. Our new model is implemented in the MHD code Athena and incorporated in the TIGRESS simulation framework, for use in studying the star-forming ISM in a wide range of environments.
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U2 - 10.3847/1538-4365/ac9b1d
DO - 10.3847/1538-4365/ac9b1d
M3 - Article
AN - SCOPUS:85145282499
SN - 0067-0049
VL - 264
JO - Astrophysical Journal, Supplement Series
JF - Astrophysical Journal, Supplement Series
IS - 1
M1 - 10
ER -