Modelling emission lines in star-forming galaxies

Baugh, CM; Lacey, Cedric G; Gonzalez-Perez, Violeta; Manzoni, Giorgio

Abstract

We present a new model to compute the luminosity of emission lines in star-forming galaxies and apply this in the semi-analytical galaxy formation code GALFORM. The model combines a pre-computed grid of H II region models with an empirical determination of how the properties of H II regions depend on the macroscopic properties of galaxies based on observations of local galaxies. The new model gives a very good reproduction of the locus of star-forming galaxies on standard line ratio diagnostic diagrams. The new model shows evolution in the locus of star-forming galaxies with redshift on this line ratio diagram, with a good match to the observed line ratios at z = 1.6. The model galaxies at high redshift have gas densities and ionisation parameters that are predicted to be ≈2–3 times higher than in local star-forming galaxies, which is partly driven by the changing selection with redshift to mimic the observational selection. Our results suggest that the observed evolution in emission line ratios requires other H II region properties to evolve with redshift, such as the gas density, and cannot be reproduced by H II model grids that only allow the gas metallicity and ionisation parameter to vary.

Citation

Baugh, C., Lacey, C. G., Gonzalez-Perez, V., & Manzoni, G. (2022). Modelling emission lines in star-forming galaxies. Monthly Notices of the Royal Astronomical Society, 510(2), 1880-1893. https://doi.org/10.1093/mnras/stab3506

• Journal Article Type: Article
• Acceptance Date: Nov 25, 2021
• Online Publication Date: Dec 3, 2021
• Publication Date: 2022-02
• Deposit Date: Feb 10, 2022
• Publicly Available Date: Feb 10, 2022
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 510
• Issue: 2
• Pages: 1880-1893
• DOI: https://doi.org/10.1093/mnras/stab3506
• Public URL: https://durham-repository.worktribe.com/output/1215646