The physical nature of circumgalactic medium absorbers in SIMBA
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Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
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 < 1011 M, 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 fromsatellites decreasing with increasing ion excitation energy.
Description
Keywords
Astronomy, Physics, Cosmology, Galaxies
Citation
Appleby, S. et al. (2023). The physical nature of circumgalactic medium absorbers in SIMBA. Monthly Notices of the Royal Astronomical Society, 519(4), 5514–5535. https://doi.org/10.1093/mnras/stad025