The Low Redshift Circumgalactic Medium in Simba
  We examine the properties of the low-redshift circumgalactic medium (CGM)
around star-forming and quenched galaxies in the Simba cosmological
hydrodynamic simulations, focusing on comparing HI and metal line absorption to
observations from the COS-Halos and COS-Dwarfs surveys. Halo baryon fractions
are generally $\lesssim 50\%$ of the cosmic fraction due to stellar feedback at
low masses, and jet-mode AGN feedback at high masses. Baryons and metals in the
CGM of quenched galaxies are $\gtrsim 90\%$ hot gas, while the CGM of
star-forming galaxies is more multi-phase. Hot CGM gas has low metallicity,
while warm and cool CGM gas have metallicity close to that of galactic gas.
Equivalent widths, covering fractions and total path absorption of HI and
selected metal lines (MgII, SiIII, CIV and OVI) around a matched sample of
Simba star-forming galaxies are mostly consistent with COS-Halos and COS-Dwarfs
observations to $\lesssim 0.4$~dex, depending on ion and assumed ionising
background. Around matched quenched galaxies, absorption in all ions is lower,
with HI absorption significantly under-predicted. Metal-line absorption is
sensitive to choice of photo-ionising background; assuming recent backgrounds,
Simba matches OVI but under-predicts low ions, while an older background
matches low ions but under-predicts OVI. Simba reproduces the observed
dichotomy of OVI absorption around star forming and quenched galaxies. CGM
metals primarily come from stellar feedback, while jet-mode AGN feedback
reduces absorption particularly for lower ions.
