The physical nature of circumgalactic medium absorbers in Simba. Issue 4 (9th January 2023)

• Record Type: Journal Article
• Authors: Appleby, Sarah; Davé, Romeel; Sorini, Daniele; Cui, Weiguang; Christiansen, Jacob
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 4(2023)
• Page Start: 5514
• Page End: 5535
• Publication Date: 2023-01-09
• Subjects: galaxies: evolution -- galaxies: general -- galaxies: haloes -- quasars: absorption lines; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stad025
• Languages: English
• ISSNs: 0035-8711

Abstract

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 ($\mbox{$M_\star $}\, > 10^{10}{\rm M}_\odot$ ) for star-forming, green valley and quenched galaxies at impact parameters r ⊥ ≤ 1.25 r 200 . 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 $\mbox{$M_\star $}\, < 10^{11}\, \, {\rm M}_{\odot }$, 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 $\sim 25{\text{--}}55{{\ \rm per\ cent}}$ for C iv and $\sim 80{\text{--}}95{{\ \rm per\ cent}}$ 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 10 r 1/2, ⋆, contributes $\sim 3{{\ \rm per\ cent}}$ of overall H i absorption but $\sim 30{{\ \rm per\ cent}}$ of Mg ii absorption, with the fraction from satellites decreasing with increasing ion excitation energy.