The Lowredshift Lyα Forest as a Constraint for Models of AGN Feedback
Abstract
We study the sensitivity of the z = 0.1 Lyα forest observables, such as the column density distribution function (CDD), flux PDF, flux power spectrum, and linewidth distribution, to subgrid models of active galactic nucleus (AGN) feedback using the Illustris and IllustrisTNG (TNG) cosmological simulations. The two simulations share an identical ultraviolet background (UVB) prescription and similar cosmological parameters, but TNG features an entirely reworked AGN feedback model. Due to changes in the AGN radiomode model, the original Illustris simulations have a factor of 23 fewer Lyα absorbers than TNG at column densities N _{H I } < 10^{15.5} cm^{2}. We compare the simulated forest statistics to UV data from the Cosmic Origins Spectrograph (COS) and find that neither simulation can reproduce the slope of the absorber distribution. Both Illustris and TNG also produce significantly smaller linewidth distributions than observed in the COS data. We show that TNG is in much better agreement with the observed z = 0.1 flux power spectrum than Illustris. We explore which statistics can disentangle the effects of AGN feedback from alternative UVB models by rescaling the UVB of Illustris to produce a CDD match to TNG. While this UVB rescaling is degenerate with the effect of AGN feedback on the CDD, the amplitude and shape of the flux PDF and 1D flux power spectrum change in a way distinct from the scaling of the UVB. Our study suggests that the z = 0.1 Lyα forest observables can be used as a diagnostic of AGN feedback models.
 Publication:

The Astrophysical Journal
 Pub Date:
 July 2022
 DOI:
 10.3847/20418213/ac7e49
 arXiv:
 arXiv:2204.09712
 Bibcode:
 2022ApJ...933L..46B
 Keywords:

 Intergalactic gas;
 Intergalactic medium;
 Lyman alpha forest;
 812;
 813;
 980;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 ApJL