CALIMA: On-the-fly dust and PAH evolution for radiation-hydrodynamics galaxy formation simulations

Abstract

Dust grains and polycyclic aromatic hydrocarbons (PAHs) actively contribute to the thermodynamics, chemistry, and radiative state of the interstellar medium (ISM), yet most ISM models and galaxy simulations either exclude them altogether or adopt simplified treatments. We present CALIMA, a new module for dust and PAH formation and evolution in radiation-hydrodynamics simulations for RAMSES, designed to self-consistently couple dust physics to radiative transfer and non-equilibrium thermochemistry in a multiphase ISM. The model employs a two-size, two-composition dust framework with log-normal grain populations, explicitly evolving stellar dust injection, turbulence-informed gas-phase accretion, shattering, coagulation, thermal and non-thermal sputtering, and shock destruction, while PAHs are separate components with their own evolution. The evolving dust populations and radiation field determine local, wavelength-dependent opacities, photoelectric heating efficiencies, grain-assisted recombination, dust-gas collisional heating/cooling, and H$_2$ formation on both grains and PAHs. Updated treatments of thermal sputtering and collisional cooling that include finite grain sizes and modern ion-solid physics reduce sputtering rates at high temperatures and extend the regime where dust significantly cools hot gas. One-zone ISM tests show that dust and PAH evolution modifies classical thermal phase diagrams and C-bearing chemistry, while isolated disc galaxy simulations reveal environment-dependent variations in dust-to-metal ratio, small-to-large grain ratio, PAH fraction, and interstellar radiation field intensity that drive non-trivial structure in infrared emission, UV transparency, and H$_2$ formation. CALIMA provides a physically motivated framework to interpret dust- and PAH-based observables and to assess dust-mediated feedback in galaxy formation across cosmic time.