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Limits on non-canonical heating and turbulence in the intergalactic medium from the low redshift Lyman α forest

Bolton, James S.; Gaikwad, Prakash; Haehnelt, Martin G.; Kim, Tae Sun; Nasir, Fahad; Puchwein, Ewald; Viel, Matteo; Wakker, Bart P.

Limits on non-canonical heating and turbulence in the intergalactic medium from the low redshift Lyman α forest Thumbnail


Prakash Gaikwad

Martin G. Haehnelt

Tae Sun Kim

Fahad Nasir

Ewald Puchwein

Matteo Viel

Bart P. Wakker


We examine the column density distribution function (CDDF) and Doppler parameter distribution from hydrodynamical simulations and Cosmic Origins Spectrograph (COS) observations of the Ly α forest at redshift 0 ≤ z ≤ 0.2. Allowing for a factor of two uncertainty in the metagalactic H I photoionization rate, our hydrodynamical simulations are in good agreement (1-1.5σ) with the shape and amplitude of the observed CDDF at H I column densities 1013.3 cm-2 ≤ NH, I ≤ 1014.5 cm-2. However, the Doppler widths of the simulated lines remain too narrow with respect to the COS data. We argue that invoking AGN feedback does not resolve this discrepancy. We also disfavour enhanced photoheating rates as a potential solution, as this requires an unphysically hard UV background spectrum. If instead appealing to a non-canonical source of heating, an additional specific heat injection of u ≲ 6.9 eV, m p-1 is required at z ≲ 2.5 for gas that has NH, I ≃ 1013.5, cm-2 by z = 0.1. Alternatively, there may be an unresolved line of sight turbulent velocity component of v turb 8.5 km, s-1 NH,I/1013.5, cm-20.21 for the coldest gas in the diffuse IGM.

Journal Article Type Article
Acceptance Date Mar 23, 2022
Online Publication Date Mar 31, 2022
Publication Date Mar 31, 2022
Deposit Date Mar 25, 2022
Publicly Available Date Apr 5, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press (OUP)
Peer Reviewed Peer Reviewed
Volume 513
Issue 1
Pages 864-885
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL
Publisher URL
Additional Information For the purpose of open access, the author has applied a creative commons attribution (CC BY) to any author accepted manuscript version arising.