A new measurement of the intergalactic temperature at z ∼ 2.55–2.95
Monthly Notices of the Royal Astronomical Society
Oxford University Press
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Rorai, A., Carswell, R., Haehnelt, M., Becker, G., Bolton, J., & Murphy, M. (2018). A new measurement of the intergalactic temperature at z ∼ 2.55–2.95. Monthly Notices of the Royal Astronomical Society, 474 (3), 2871-2883. https://doi.org/10.1093/mnras/stx2862
We present two measurements of the temperature–density relationship (TDR) of the intergalactic medium (IGM) in the redshift range 2.55 < z < 2.95 using a sample of 13 high-quality quasar spectra and high resolution numerical simulations of the IGM. Our approach is based on fitting the neutral hydrogen column density NHI and the Doppler parameter b of the absorption lines in the Lyα forest. The first measurement is obtained using a novel Bayesian scheme that takes into account the statistical correlations between the parameters characterizing the lower cut-off of the b--NHI distribution and the power-law parameters T0 and γ describing the TDR. This approach yields T0/103 K = 15.6 ± 4.4 and γ = 1.45 ± 0.17 independent of the assumed pressure smoothing of the small-scale density field. In order to explore the information contained in the overall b--NHI distribution rather than only the lower cut-off, we obtain a second measurement based on a similar Bayesian analysis of the median Doppler parameter for separate column-density ranges of the absorbers. In this case, we obtain T0/103 K = 14.6 ± 3.7 and γ = 1.37 ± 0.17 in good agreement with the first measurement. Our Bayesian analysis reveals strong anticorrelations between the inferred T0 and γ for both methods as well as an anticorrelation of the inferred T0 and the pressure smoothing length for the second method, suggesting that the measurement accuracy can in the latter case be substantially increased if independent constraints on the smoothing are obtained. Our results are in good agreement with other recent measurements of the thermal state of the IGM probing similar (over-)density ranges.
intergalactic medium, quasars: absorption lines
MH acknowledges support by ERC ADVANCED GRANT 320596 ‘The Emergence of Structure during the epoch of Reionization’. GDB was supported by the National Science Foundation through grant AST-1615814. JSB acknowledges the support of a Royal Society University Research Fellowship. MTM thanks the Australian Research Council for Discovery Project grant DP130100568. This work made use of the DiRAC High Performance Computing System (HPCS) and the COSMOS shared memory service at the University of Cambridge. These are operated on behalf of the STFC DiRAC HPC facility. This equipment is funded by BIS National E-infrastructure capital grant ST/J005673/1 and STFC grants ST/H008586/1, ST/K00333X/1.
European Research Council (320596)
Leverhulme Trust (EM/4/EM/2008/0053)
External DOI: https://doi.org/10.1093/mnras/stx2862
This record's URL: https://www.repository.cam.ac.uk/handle/1810/276875