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The thermal history of the intergalactic medium down to redshift z=1.5: a new curvature measurement

Boera, Elisa; Murphy, Michael T.; Becker, George D.; Bolton, James S.


Elisa Boera

Michael T. Murphy

George D. Becker

James S. Bolton


According to the photoheating model of the intergalactic medium (IGM), He ii reionization is expected to affect its thermal evolution. Evidence for additional energy injection into the IGM has been found at 3 ≲ z ≲ 4, though the evidence for the subsequent fall-off below z ∼ 2.8 is weaker and depends on the slope of the temperature–density relation, γ. Here we present, for the first time, an extension of the IGM temperature measurements down to the atmospheric cut-off of the H i Lyman-α (Lyα) forest at z ≃ 1.5. Applying the curvature method on a sample of 60 Ultraviolet and Visual Echelle Spectrograph (UVES) spectra we investigated the thermal history of the IGM at z < 3 with precision comparable to the higher redshift results. We find that the temperature of the cosmic gas traced by the Lyα forest [T(Δ¯)] increases for increasing overdensity from T(Δ¯)∼22670 to 33740 K in the redshift range z ∼ 2.8–1.6. Under the assumption of two reasonable values for γ, the temperature at the mean density (T0) shows a tendency to flatten at z ≲ 2.8. In the case of γ ∼ 1.5, our results are consistent with previous ones which indicate a falling T0 for redshifts z ≲ 2.8. Finally, our T(Δ¯) values show reasonable agreement with moderate blazar heating models.


Boera, E., Murphy, M. T., Becker, G. D., & Bolton, J. S. (2014). The thermal history of the intergalactic medium down to redshift z=1.5: a new curvature measurement. Monthly Notices of the Royal Astronomical Society, 441(3),

Journal Article Type Article
Acceptance Date Mar 30, 2014
Publication Date May 16, 2014
Deposit Date May 4, 2017
Publicly Available Date May 4, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 441
Issue 3
Keywords intergalactic medium, quasars: absorption lines, cosmology: observations
Public URL
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