The Interstellar Medium and Star Formation of Galactic Disks. I. ISM and GMC properties with Diffuse FUV and Cosmic Ray Backgrounds

Abstract

We present a series of adaptive mesh refinement (AMR) hydrodynamic simulations of flat rotation curve galactic gas disks with a detailed treatment of the interstellar medium (ISM) physics of the atomic to molecular phase transition under the influence of diffuse FUV radiation fields and cosmic ray backgrounds. We explore the effects of different FUV intensities, including a model with a radial gradient designed to mimic the Milky Way. The effects of cosmic rays, including radial gradients in their heating and ionization rates, are also explored. The final simulations in this series achieve $4$pc resolution across the $\sim 20$kpc global disk diameter, with heating and cooling followed down to temperatures of $\sim 10$K. The disks are evolved for $300$Myr, which is enough time for the ISM to achieve a quasi-statistical equilibrium. In particular, the mass fraction of molecular gas stabilizes by $\sim$200 Myr. Additional global ISM properties are analysed. Giant molecular clouds (GMCs) are also identified and the statistical properties of their populations examined. GMCs are tracked as the disks evolve. GMC collisions, which may be a means of triggering star cluster formation, are counted and the rates compared with analytic models. Relatively frequent GMC collision rates are seen in these simulations and their implications for understanding GMC properties, including the driving of internal turbulence, are discussed.

Accepted by PASJ (cloud-cloud collision special issue)

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• Photodissociation Region Diagnostics Across Galactic Environments
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) : Molecular clouds toward W33 ; possible evidence for a cloud-cloud collision triggering O star formation
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy: cloud population statistics
• PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions
• SiO emission as a probe of Cloud-Cloud Collisions in Infrared Dark Clouds
• The KOSMA-$\tau$ PDR Model -- I. Recent updates to the numerical model of photo-dissociated regions
• Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI
• WISDOM Project -- XV. Giant Molecular Clouds in the Central Region of the Barred Spiral Galaxy NGC 5806
• WISDOM Project XII. Clump properties and turbulence regulated by clump-clump collisions in the dwarf galaxy NGC404
• Investigating the Upper Scorpius OB association with HERMES. I. The spectroscopic sample and 6D kinematics
• GMC Collisions As Triggers of Star Formation. VIII. The Core Mass Function
• CO Depletion in Infrared Dark Clouds