paper

How baryons affect halos and large-scale structure: a unified picture from the Simba simulation

arXiv:2111.13708 · doi:10.1093/mnras/stac2214

Abstract

Using the state-of-the-art suite of hydrodynamic simulations Simba, as well as its dark-matter-only counterpart, we study the impact of the presence of baryons and of different stellar/AGN feedback mechanisms on large-scale structure, halo density profiles, and on the abundance of different baryonic phases within halos and in the intergalactic medium (IGM). The unified picture that emerges from our analysis is that the main physical drivers shaping the distribution of matter at all scales are star formation-driven galactic outflows at for lower mass halos and AGN jets at in higher mass halos. Feedback suppresses the baryon mass function with time relative to the halo mass function, and it even impacts the halo mass function itself at the ~20% level, particularly evacuating the centres and enhancing dark matter just outside halos. At early epochs baryons pile up in the centres of halos, but by late epochs and particularly in massive systems gas has mostly been evacuated from within the inner halo. AGN jets are so efficient at such evacuation that at low redshifts the baryon fraction within halos is only 25% of the cosmic baryon fraction, mostly in stars. The baryon fraction enclosed in a sphere around such halos approaches the cosmic value only at 10-20 virial radii. As a result, 87% of the baryonic mass in the Universe lies in the IGM at , with 67% being in the form of warm-hot IGM ().

Published in the Monthly Notices of the Royal Astronomical Society (MNRAS). This is a pre-copyedited, author-produced version of the article accepted for publication in MNRAS following peer review. The version of record (MNRAS, Vol. 516, Issue 1, pp. 883-906) is available online at: DOI 10.1093/mnras/stac2214 . Minor updates to text and some figures wrt previous version. Conclusions unchanged

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