The effect of stellar and AGN feedback on the low redshift Lyman-$\alpha$ forest in the Sherwood simulation suite

Abstract

We study the effect of different feedback prescriptions on the properties of the low redshift ($z\le 1.6$) Ly$\alpha$ forest using a selection of hydrodynamical simulations drawn from the Sherwood simulation suite. The simulations incorporate stellar feedback, AGN feedback and a simplified scheme for efficiently modelling the low column density Ly$\alpha$ forest. We confirm a discrepancy remains between Cosmic Origins Spectrograph (COS) observations of the Ly$\alpha$ forest column density distribution function (CDDF) at $z\simeq 0.1$ for high column density systems ($N_{\mathrm{HI}}>10^{14}\mathrm{c}{\mathrm{m}}^{-2}$), as well as Ly$\alpha$ velocity widths that are too narrow compared to the COS data. Stellar or AGN feedback -- as currently implemented in our simulations -- have only a small effect on the CDDF and velocity width distribution. We conclude that resolving the discrepancy between the COS data and simulations requires an increase in the temperature of overdense gas with $\Delta =4$--$40$, either through additional He$\mathrm{II}$ photo-heating at $z>2$ or fine-tuned feedback that ejects overdense gas into the IGM at just the right temperature for it to still contribute significantly to the Ly$\alpha$ forest. Alternatively a larger, currently unresolved turbulent component to the line width could resolve the discrepancy.

16 pages, 8 figures, Accepted to MNRAS

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Cited by in corpus (8)

• Limits on non-canonical heating and turbulence in the intergalactic medium from the low redshift Lyman-alpha forest
• The low redshift Lyman-$\alpha$ Forest as a constraint for models of AGN feedback
• The evolution of the low-density HI intergalactic medium from z=3.6 to 0: Data, transmitted flux and HI column density
• A Novel Statistical Method for Measuring the Temperature-Density Relation in the IGM Using the $b$-$N_{\text{HI}}$ Distribution of Absorbers in the Ly$\alpha$ Forest
• Can the Low Redshift Lyman Alpha Forest Constrain AGN Feedback Models?
• Measuring the thermal and ionization state of the low-$z$ IGM using likelihood free inference
• Role of ionizing background on the non-thermal broadening inferred for the aligned absorbers
• Measurement of redshift-space two- and three-point correlation of Ly$\alpha$ absorbers at $1.7<z<3.5$: Implications on evolution of the physical properties of IGM