Zero flux troughs by different Lyman absorbers in the spectrum of first confirmed observation of the effect.[2]
For over three decades after the prediction, no objects had been found distant enough to show the Gunn–Peterson trough. It was not until 2001, with the discovery of a quasar with a redshift z = 6.28 by Robert Becker and others[2] using data from the Sloan Digital Sky Survey, that a Gunn–Peterson trough was finally observed. The article also included quasars at redshifts of z = 5.82 and z = 5.99, and, while each of these exhibited absorption at wavelengths on the blue side of the Lyman-alpha transition, there were numerous spikes in flux as well. The flux of the quasar at z = 6.28, however, was effectively zero beyond the Lyman-alpha limit, meaning that the neutral hydrogen fraction in the IGM must have been larger than ~10−3.
The discovery of the trough in a z = 6.28 quasar, and the absence of the trough in quasars detected at redshifts just below z = 6 presented strong evidence for the hydrogen in the universe having undergone a transition from neutral to ionized around z = 6. After recombination, the universe was expected to be neutral, until the first objects in the universe started emitting light and energy which would reionize the surrounding IGM. However, as the scattering cross section of photons with energies near that of the Lyman-alpha limit with neutral hydrogen is very high, even a small fraction of neutral hydrogen will make the optical depth of the IGM high enough to cause the suppression of emission observed. Despite the fact that the ratio of neutral hydrogen to ionized hydrogen may not have been particularly high, the low flux observed past the Lyman-alpha limit indicates that the universe was in the final stages of reionization.
Following the first release of data from the WMAP spacecraft in 2003, the determination by Becker that the end of reionization occurred at z ≈ 6 appeared to conflict with estimates made from the WMAP measurement of the electron column density.[3] However, the WMAP III data released in 2006 now seems to be in much better agreement with the limits on reionization placed by observation of the Gunn–Peterson trough.[4]
^Gunn, J. E.; Peterson, B. A. (1965). "On the Density of Neutral Hydrogen in Intergalactic Space". Astrophysical Journal. 142: 1633–1641. Bibcode:1965ApJ...142.1633G. doi:10.1086/148444.
^ abBecker, R. H.; et al. (2001). "Evidence For Reionization at z ~ 6: Detection of a Gunn–Peterson Trough in a z = 6.28 Quasar". Astronomical Journal. 122 (6): 2850–2857. arXiv:astro-ph/0108097. Bibcode:2001AJ....122.2850B. doi:10.1086/324231. S2CID 14117521.
gunn, peterson, trough, astronomical, spectroscopy, feature, spectra, quasars, presence, neutral, hydrogen, intergalactic, medium, trough, characterized, suppression, electromagnetic, emission, from, quasar, wavelengths, less, than, that, lyman, alpha, line, r. In astronomical spectroscopy the Gunn Peterson trough is a feature of the spectra of quasars due to the presence of neutral hydrogen in the Intergalactic medium IGM The trough is characterized by suppression of electromagnetic emission from the quasar at wavelengths less than that of the Lyman alpha line at the redshift of the emitted light This effect was originally predicted in 1965 by James E Gunn and Bruce Peterson 1 Contents 1 First detection 2 Evidence for reionization 3 See also 4 ReferencesFirst detection edit nbsp Zero flux troughs by different Lyman absorbers in the spectrum of first confirmed observation of the effect 2 For over three decades after the prediction no objects had been found distant enough to show the Gunn Peterson trough It was not until 2001 with the discovery of a quasar with a redshift z 6 28 by Robert Becker and others 2 using data from the Sloan Digital Sky Survey that a Gunn Peterson trough was finally observed The article also included quasars at redshifts of z 5 82 and z 5 99 and while each of these exhibited absorption at wavelengths on the blue side of the Lyman alpha transition there were numerous spikes in flux as well The flux of the quasar at z 6 28 however was effectively zero beyond the Lyman alpha limit meaning that the neutral hydrogen fraction in the IGM must have been larger than 10 3 Evidence for reionization editSee also Reionization The discovery of the trough in a z 6 28 quasar and the absence of the trough in quasars detected at redshifts just below z 6 presented strong evidence for the hydrogen in the universe having undergone a transition from neutral to ionized around z 6 After recombination the universe was expected to be neutral until the first objects in the universe started emitting light and energy which would reionize the surrounding IGM However as the scattering cross section of photons with energies near that of the Lyman alpha limit with neutral hydrogen is very high even a small fraction of neutral hydrogen will make the optical depth of the IGM high enough to cause the suppression of emission observed Despite the fact that the ratio of neutral hydrogen to ionized hydrogen may not have been particularly high the low flux observed past the Lyman alpha limit indicates that the universe was in the final stages of reionization Following the first release of data from the WMAP spacecraft in 2003 the determination by Becker that the end of reionization occurred at z 6 appeared to conflict with estimates made from the WMAP measurement of the electron column density 3 However the WMAP III data released in 2006 now seems to be in much better agreement with the limits on reionization placed by observation of the Gunn Peterson trough 4 See also edit nbsp Astronomy portal Lyman alpha forestReferences edit Gunn J E Peterson B A 1965 On the Density of Neutral Hydrogen in Intergalactic Space Astrophysical Journal 142 1633 1641 Bibcode 1965ApJ 142 1633G doi 10 1086 148444 a b Becker R H et al 2001 Evidence For Reionization at z 6 Detection of a Gunn Peterson Trough in a z 6 28 Quasar Astronomical Journal 122 6 2850 2857 arXiv astro ph 0108097 Bibcode 2001AJ 122 2850B doi 10 1086 324231 S2CID 14117521 Kogut A et al 2003 First Year Wilkinson Microwave Anisotropy Probe WMAP Observations Temperature Polarization Correlation Astrophysical Journal Supplement Series 148 1 161 173 arXiv astro ph 0302213 Bibcode 2003ApJS 148 161K doi 10 1086 377219 S2CID 15253442 Page L et al 2007 Three Year Wilkinson Microwave Anisotropy Probe WMAP Observations Polarization Analysis Astrophysical Journal Supplement Series 170 2 335 376 arXiv astro ph 0603450 Bibcode 2007ApJS 170 335P doi 10 1086 513699 S2CID 12113374 Retrieved from https en wikipedia org w index php title Gunn Peterson trough amp oldid 1223095982, wikipedia, wiki, book, books, library,
