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Abstract Active galactic nuclei (AGNs) feedback models are generally calibrated to reproduce galaxy observables such as the stellar mass function and the bimodality in galaxy colors. We use variations of the AGN feedback implementations in the IllustrisTNG (TNG) andSimbacosmological hydrodynamic simulations to show that the low-redshift Lyαforest can provide constraints on the impact of AGN feedback. We show that TNG overpredicts the number density of absorbers at column densitiesNHI< 1014cm−2compared to data from the Cosmic Origins Spectrograph (in agreement with previous work), and we demonstrate explicitly that its kinetic feedback mode, which is primarily responsible for galaxy quenching, has a negligible impact on the column density distribution (CDD) of absorbers. In contrast, we show that the fiducialSimbamodel, which includes AGN jet feedback, is the preferred fit to the observed CDD of thez= 0.1 Lyαforest across 5 orders of magnitude in column density. We show that theSimbaresults with jets produce a quantitatively better fit to the observational data than theSimbaresults without jets, even when the ultraviolet background is left as a free parameter. AGN jets inSimbaare high speed, collimated, weakly interacting with the interstellar medium (via brief hydrodynamic decoupling), and heated to the halo virial temperature. Collectively these properties result in stronger long-range impacts on the intergalactic medium when compared to TNG’s kinetic feedback mode, which drives isotropic winds with lower velocities at the galactic radius. Our results suggest that the low-redshift Lyαforest provides plausible evidence for long-range AGN jet feedback.
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This content will become publicly available on February 5, 2026
The Effects of Active Galactic Nuclei Feedback on the Lyα Forest Flux Power Spectrum
Abstract We study the effects of active galactic nuclei (AGN) feedback on the Lyαforest 1D flux power spectrum (P1D). Using theSimbacosmological-hydrodynamic simulations, we examine the impact that adding different AGN feedback modes has on the predicted P1D. We find that, forSimba, the impact of AGN feedback is most dramatic at lower redshifts (z < 1) and that AGN jet feedback plays the most significant role in altering the P1D. The effects of AGN feedback can be seen across a large range of wavenumbers (1.5 × 10−3 < k < 10−1s km−1) changing the ionization state of hydrogen in the IGM through heating. AGN feedback can also alter the thermal evolution of the IGM and thermally broaden individual Lyαabsorbers. For theSimbamodel, these effects become observable atz ≲ 1.0. At higher redshifts (z > 2.0), AGN feedback has a 2% effect on the P1D fork < 5 × 10−2s km−1and an 8% effect fork > 5 × 10−2s km−1. We show that the small-scale effect is reduced when normalizing the simulation to the observed mean flux. On large scales, the effect of AGN feedback appears via a change in the IGM temperature and is thus unlikely to bias cosmological parameters. The strong AGN jets in theSimbasimulation can reproduce thez > 2 Lyαforest. We stress that analyses comparing different AGN feedback models to future higher precision data will be necessary to determine the full extent of this effect.
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- Award ID(s):
- 2006176
- PAR ID:
- 10643624
- Publisher / Repository:
- American Astronomical Society
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 980
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 72
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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