2025/05/18 by Yurina Nakazato, Kazuyuki Sugimura, Nakazato, Yurina +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.2505.12397
openalex publication_date 2025/05/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Recent multi-wavelength observations by JWST and ALMA are unveiling both ionized and neutral ISM components in high-redshift (z>6) galaxies. In this work, we investigate the origin of rest-frame far-infrared [OIII]88 μm and [CII]158 μm emission by performing zoom-in cosmological simulations of dwarf-galaxy progenitors at z=9-13. Our simulations incorporate on-the-fly radiative transfer at sub-pc (∼ 0.1 pc) resolution, allowing us to resolve the multi-phase ISM. We compute emission lines on a cell-by-cell basis, taking into account local temperature, density, metallicity, radiation field strength, column density, and spectral hardness of radiation bins. We find that [OIII] predominantly arises from centrally located ionizing bubbles with temperatures of ∼ (1-5)× 104 K and high ionization parameters of log Uion ≃ -1.5. In contrast, [CII] is produced in the surrounding dense neutral regions at ∼ 5× 103 K, which are heated by strong FUV radiation (G/G0 ∼ 103-5) from the central stellar clusters. This spatial arrangement leads to large local variations in [OIII]/[CII], ranging from ∼ 100 to 0.01. Our galaxy reproduces the global ratio [OIII]/[CII]∼5-30, consistent with recent ALMA detections at z>6 without invoking enhanced O/C abundance ratios. We further derive that [OIII]/[CII] linearly scales with the mass and density ratios of ionized to neutral gas, M\rm HII/M\rm HI and n\rm HII/n\rm HI and show that the [OIII]/[CII] ratio typically changes from 5.7 to 0.3 from high-z to low-z. For future synergies of JWST and ALMA, we derived M\rm HII/M\rm HI for observed z >6 galaxies using \rm Hβ and [CII] and show the validity of our scaling relations.