The Gunn-Peterson Trench — in astronomical spectroscopy, is a feature of the spectra of quasars due to the presence of neutral hydrogen in the intergalactic medium . The gutter is characterized by the suppression of electromagnetic radiation of a quasar at wavelengths less than that of the Lyman-alpha line with a red shift of the emitted light. This effect was originally predicted in 1965 by James Gann and Bruce Peterson. [one]
Content
First detection
For more than three decades after the prediction, no object was found far enough to show the Gann-Peterson cavity. Only in 2001, when Robert Becker and others [2] , using data from the Sloan Digital Sky Survey , discovered a quasar with a redshift of z = 6.28, the trough of Gunn-Peterson was finally discovered. The document also includes quasars with redshifts from Z = 5.82 and Z = 5.99, and, although each of them showed absorption at wavelengths on the blue side of the Lyman-alpha transition, there were also numerous bursts of flow. However, the quasar flow at z = 6.28 was virtually zero beyond the Lyman-alpha limit, which means that the proportion of neutral hydrogen in the intergalactic medium should have been greater than ~ 10 −3 .
Evidence of Reionization
The discovery of a depression in a quasar with z = 6.28 and the absence of a depression in quasars found at redshifts slightly below z = 6 are convincing evidence that hydrogen in the Universe underwent a transition from neutral to ionized around z = 6. After recombination, the universe was supposed to be neutral until the first objects in the universe began to emit light and energy that could reionize the surrounding intergalactic environment. However, since the cross section for the scattering of photons with energies close to the limit of the estuary alpha with neutral hydrogen is very large, even a small fraction of neutral hydrogen will make the optical thickness of the intergalactic medium high enough to cause suppression of the observed radiation. Although the ratio of neutral hydrogen to ionized hydrogen may not have been particularly high, the low flux observed outside the Estuary-alpha indicates that the Universe was in the last stages of reionization.
After the first release of data from the WMAP spacecraft in 2003, Becker’s determination that the end of reionization occurred at z ≈ 6 seemed to contradict the estimates made from the WMAP density measurement of electronic speakers. [3] However, the WMAP III data published in 2006 now appears to be in much better agreement with the reionization restrictions established when observing the Gunn-Peterson Trench. [four]
See also
- Forest Lyman-alpha
Links
- ↑ Gunn, JE On the Density of Neutral Hydrogen in Intergalactic Space (English) // The Astrophysical Journal : journal. - IOP Publishing , 1965. - Vol. 142 - P. 1633—1641 . - DOI : 10.1086 / 148444 . - .
- ↑ Becker, RH Evidence For Reionization at z ~ 6: Detection of a Gunn-Peterson Trough in az = 6.28 Quasar (Eng.) // Astronomical Journal : journal. - 2001. - Vol. 122 , no. 6 - P. 2850-2857 . - DOI : 10.1086 / 324231 . - . - arXiv : astro-ph / 0108097 .
- Og Kogut, A. First-Years Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature-Polarization Correlation (Eng.) // The Astrophysical Journal : journal. - IOP Publishing 2003. - Vol. 148 , no. 1 . - P. 161-173 . - DOI : 10.1086 / 377219 . - . - arXiv : astro-ph / 0302213 .
- Kins Page, L. Three-Years Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis (Eng.) // The Astrophysical Journal : journal. - IOP Publishing , 2007. - Vol. 170 , no. 2 - P. 335-376 . - DOI : 10.1086 / 513699 . - . - arXiv : astro-ph / 0603450 .