The physical nature of circumgalactic medium absorbers in Simba

Appleby, Sarah; Davé, Romeel; Sorini, Daniele; Cui, Weiguang; Christiansen, Jacob

Abstract

We study the nature of the low-redshift circumgalactic medium (CGM) in the SIMBA  cosmological simulations as traced by ultraviolet absorption lines around galaxies in bins of stellar mass (⁠M⋆>1010M⊙⁠) for star-forming, green valley and quenched galaxies at impact parameters r⊥ ≤ 1.25r200. We generate synthetic spectra for H I , Mg II , C II , Si III , C IV , and O VI , fit Voigt profiles to obtain line properties, and estimate the density, temperature, and metallicity of the absorbing gas. We find that CGM absorbers are most abundant around star-forming galaxies with M⋆<1011M⊙⁠, while the abundance of green valley galaxies show similar behaviour to those of quenched galaxies, suggesting that the CGM ‘quenches’ before star formation ceases. H I  absorbing gas exists across a broad range of cosmic phases [condensed gas, diffuse gas, hot halo gas, and Warm-Hot Intergalactic Medium (WHIM)], while essentially all low ionization metal absorption arises from condensed gas. O VI absorbers are split between hot halo gas and the WHIM. The fraction of collisionally ionized CGM absorbers is ∼25--55 per cent for C IV  and ∼80--95 per cent for O VI , depending on stellar mass and impact parameter. In general, the highest column density absorption features for each ion arise from dense gas. Satellite gas, defined as that within 10r1/2,⋆, contributes ∼3 per cent of overall H I absorption but ∼30 per cent of Mg II  absorption, with the fraction from satellites decreasing with increasing ion excitation energy.

Citation

Appleby, S., Davé, R., Sorini, D., Cui, W., & Christiansen, J. (2023). The physical nature of circumgalactic medium absorbers in Simba. Monthly Notices of the Royal Astronomical Society, 519(4), 5514-5534. https://doi.org/10.1093/mnras/stad025

• Journal Article Type: Article
• Acceptance Date: Jan 4, 2023
• Online Publication Date: Jan 9, 2023
• Publication Date: 2023
• Deposit Date: May 10, 2023
• Publicly Available Date: May 10, 2023
• 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: 519
• Issue: 4
• Pages: 5514-5534
• DOI: https://doi.org/10.1093/mnras/stad025
• Public URL: https://durham-repository.worktribe.com/output/1173101