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SILCC-FUV: The Influence of Far-Ultraviolet Radiation on Star Formation and the Interstellar Medium

Figure 1. Overview of the simulated ISM. Shown are the edge-on views of the total gas (Σgas, 1st panel), molecular hydrogen (ΣH2, 4th panel), and ionized hydrogen (ΣH+, 5th panel) column densities, as well as mass-weighted gas (Tgas, 2nd panel) and dust (Tdust, 3rd panel) temperatures and ionizing photon energy density (eγ, 6th panel), the effective G0 field (Geff, 7th panel), and cosmic ray energy density (eCR, 8th panel) in projection. The star-forming galactic ISM is concentrated around the midplane. White circles in the 1st panel indicate active star clusters.

Tim-Eric Rathjen

What roles do different stellar feedback processes play in governing star formation? From ionizing and non-ionizing radiation to stellar winds and supernovae, these forces interact with the surrounding stellar nurseries. However, understanding the precise significance of each process in shaping star formation remains an ongoing challenge.

We present new magneto-hydrodynamic (MHD) simulations conducted within the SILCC framework, exploring the multiphase interstellar medium (ISM) within a patch of a stratified galactic disk. Our study incorporates a self-consistent modeling of non-ionizing far-ultraviolet (FUV) radiation emitted by stellar clusters, aiming to understand its impact on star formation and the chemical composition of the nearby ISM. We observe locally intense interstellar radiation fields (ISRF) with values up to G0 ≈ 104 (in Habing units), contrasting with the canonical solar neighborhood value of G0 = 1.7.

Our findings suggest that while FUV radiation influences star formation, its role in regulating the star formation rate (SFR) appears less significant compared to other stellar feedback mechanisms such as ionizing UV radiation, stellar winds, and supernovae. Additionally, our chemical analysis reveals enhancements in both the warm-ionized medium (WIM) and the cold-neutral medium (CNM) beyond the vicinity of stellar clusters, indicating a complex interplay influenced by the self-consistent and highly variable FUV radiation field, fostering the presence of a diffuse molecular hydrogen gas phase.

Further details will be available in Rathjen et al., currently in preparation.