A new measurement of the intergalactic temperature at z∼2.55 − 2.95
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...
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| Format: | Article |
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Oxford University Press
2017
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| Online Access: | https://eprints.nottingham.ac.uk/48434/ |
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| author | Rorai, Alberto Carswell, R.F. Haehnelt, Martin G. Becker, George D. Bolton, James S. Murphy, Michael T. |
| author_facet | Rorai, Alberto Carswell, R.F. Haehnelt, Martin G. Becker, George D. Bolton, James S. Murphy, Michael T. |
| author_sort | Rorai, Alberto |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | 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 which takes into account the statistical correlations between the parameters characterising 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 anti-correlations between the inferred T0 and γ for both methods as well as an anti-correlation 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. |
| first_indexed | 2025-11-14T20:09:01Z |
| format | Article |
| id | nottingham-48434 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T20:09:01Z |
| publishDate | 2017 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-484342020-05-04T19:16:43Z https://eprints.nottingham.ac.uk/48434/ A new measurement of the intergalactic temperature at z∼2.55 − 2.95 Rorai, Alberto Carswell, R.F. Haehnelt, Martin G. Becker, George D. Bolton, James S. Murphy, Michael T. 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 which takes into account the statistical correlations between the parameters characterising 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 anti-correlations between the inferred T0 and γ for both methods as well as an anti-correlation 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. Oxford University Press 2017-11-07 Article PeerReviewed Rorai, Alberto, Carswell, R.F., Haehnelt, Martin G., Becker, George D., Bolton, James S. and Murphy, Michael T. (2017) A new measurement of the intergalactic temperature at z∼2.55 − 2.95. Monthly Notices of the Royal Astronomical Society, 474 (3). pp. 2871-2883. ISSN 1365-2966 intergalactic medium; quasar:absorption lines https://academic.oup.com/mnras/article/474/3/2871/4600557 doi:10.1093/mnras/stx2862 doi:10.1093/mnras/stx2862 |
| spellingShingle | intergalactic medium; quasar:absorption lines Rorai, Alberto Carswell, R.F. Haehnelt, Martin G. Becker, George D. Bolton, James S. Murphy, Michael T. A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title | A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title_full | A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title_fullStr | A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title_full_unstemmed | A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title_short | A new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| title_sort | new measurement of the intergalactic temperature at z∼2.55 − 2.95 |
| topic | intergalactic medium; quasar:absorption lines |
| url | https://eprints.nottingham.ac.uk/48434/ https://eprints.nottingham.ac.uk/48434/ https://eprints.nottingham.ac.uk/48434/ |