Jet feedback and the photon underproduction crisis in SIMBA
Loading...
Date
2020-10-01
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
Abstract
We examine the impact of black hole jet feedback on the properties of the low-redshift intergalactic medium (IGM) in the SIMBA
simulation, with a focus on the Lyα forest mean flux decrement DA. Without jet feedback, we confirm the photon underproduction
crisis (PUC) in which H I at z = 0 must be increased by 6 times over the Haardt & Madau value in order to match the observed DA.
Turning on jet feedback lowers this discrepancy to ∼2.5 times, and additionally using the recent Faucher–Giguere background `
mostly resolves the PUC, along with producing a flux probability distribution function in accord with observations. The PUC
becomes apparent at late epochs (z 1) where the jet and no-jet simulations diverge; at higher redshifts SIMBA reproduces the
observed DA with no adjustment, with or without jets. The main impact of jet feedback is to lower the cosmic baryon fraction in
the diffuse IGM from 39 per cent to 16 per cent at z = 0, while increasing the warm-hot intergalactic medium (WHIM) baryon
fraction from 30 per cent to 70 per cent; the lowering of the diffuse IGM content directly translates into a lowering of DA by a
similar factor. Comparing to the older MUFASA simulation that employs different quenching feedback but is otherwise similar
to SIMBA, MUFASA matches DA less well than SIMBA, suggesting that low-redshift measurements of DA and H I could provide
constraints on feedback mechanisms. Our results suggest that widespread IGM heating at late times is a plausible solution to the
PUC, and that SIMBA’s jet active galactic nucleus feedback model, included to quench massive galaxies, approximately yields
this required heating.
Description
Keywords
methods: numerical – galaxies, evolution – galaxies, formation – intergalactic medium, quasars: absorption lines
Citation
Dave, R et al. 2020. Jet feedback and the photon underproduction crisis in SIMBA. Monthly Notices of the Royal Astronomical Society. 499(2):2617-2635