Misplaced Pages

Reionization

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
(Redirected from Epoch of Reionisation) Process that caused matter to reionize early in the history of the Universe
Part of a series on
Physical cosmology
Full-sky image derived from nine years' WMAP data
Early universe
Backgrounds
Expansion · Future
Components · Structure
Components
Structure
Experiments
Scientists
Subject history
Nature timeline
This box:
−13 —–−12 —–−11 —–−10 —–−9 —–−8 —–−7 —–−6 —–−5 —–−4 —–−3 —–−2 —–−1 —–0 —Dark AgesReionizationMatter-dominated
eraAccelerated expansionWater on EarthSingle-celled lifePhotosynthesisMulticellular
lifeVertebrates
←Earliest Universe
←Earliest stars
←Earliest galaxy
←Earliest quasar / black hole
←Omega Centauri
←Andromeda Galaxy
←Milky Way spirals
←NGC 188 star cluster
←Alpha Centauri
←Earth / Solar System
←Earliest known life
←Earliest oxygen
←Atmospheric oxygen
←Sexual reproduction
←Earliest fungi
←Earliest animals / plants
←Cambrian explosion
←Earliest mammals
←Earliest apes / humans
L
i
f
e
(billion years ago)
Phases of the reionization

In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".

Reionization is the second of two major phase transitions of gas in the universe (the first is recombination). While the majority of baryonic matter in the universe is in the form of hydrogen and helium, reionization usually refers strictly to the reionization of hydrogen, the element.

It is believed that the primordial helium also experienced a similar reionization phase change, but at a later epoch in the history of the universe. This is usually called "helium reionization".

Background

Schematic timeline of the universe, depicting reionization's place in cosmic history.

The first phase change of hydrogen in the universe was recombination, which occurred at a redshift z = 1089 (379,000 years after the Big Bang), due to the cooling of the universe to the point where the rate of recombination of electrons and protons to form neutral hydrogen was higher than the reionization rate. The universe was opaque before the recombination, due to the scattering of photons of all wavelengths off free electrons (and free protons, to a significantly lesser extent), but it became increasingly transparent as more electrons and protons combined to form neutral hydrogen atoms. While the electrons of neutral hydrogen can absorb photons of some wavelengths by rising to an excited state, a universe full of neutral hydrogen will be relatively opaque only at those few wavelengths. The remaining light could travel freely and become the cosmic microwave background radiation. The only other light at this point would be provided by those excited hydrogen atoms, marking the beginning of an era called the Dark Ages of the universe.

The second phase change occurred once gas clouds started to condense in the early universe that were energetic enough to re-ionize neutral hydrogen. As these objects formed and radiated energy, the universe reverted from being composed of neutral atoms, to once again being an ionized plasma. This occurred between 150 million and one billion years after the Big Bang (at a redshift 20 > z > 6). At that time, however, matter had been diffused by the expansion of the universe, and the scattering interactions of photons and electrons were much less frequent than before electron-proton recombination. Thus, the universe was full of low density ionized hydrogen and remained transparent, as is the case today.

Detection methods

Looking back so far in the history of the universe presents some observational challenges. There are, however, a few observational methods for studying reionization.

Quasars and the Gunn-Peterson trough

One means of studying reionization uses the spectra of distant quasars. Quasars release an extraordinary amount of energy, being among the brightest objects in the universe. As a result, some quasars are detectable from as long ago as the epoch of reionization. Quasars also happen to have relatively uniform spectral features, regardless of their position in the sky or distance from the Earth. Thus it can be inferred that any major differences between quasar spectra will be caused by the interaction of their emission with atoms along the line of sight. For wavelengths of light at the energies of one of the Lyman transitions of hydrogen, the scattering cross-section is large, meaning that even for low levels of neutral hydrogen in the intergalactic medium (IGM), absorption at those wavelengths is highly likely.

For nearby objects in the universe, spectral absorption lines are very sharp, as only photons with energies just sufficient to cause an atomic transition can cause that transition. However, the distances between quasars and the telescopes which detect them are large, which means that the expansion of the universe causes light to undergo noticeable redshifting. This means that as light from the quasar travels through the IGM and is redshifted, wavelengths which had been below the Lyman Alpha limit are stretched, and will in effect begin to fill in the Lyman absorption band. This means that instead of showing sharp spectral absorption lines, a quasar's light which has traveled through a large, spread out region of neutral hydrogen will show a Gunn-Peterson trough.

The redshifting for a particular quasar provides temporal information about reionization. Since an object's redshift corresponds to the time at which it emitted the light, it is possible to determine when reionization ended. Quasars below a certain redshift (closer in space and time) do not show the Gunn-Peterson trough (though they may show the Lyman-alpha forest), while quasars emitting light prior to reionization will feature a Gunn-Peterson trough. In 2001, four quasars were detected by the Sloan Digital Sky Survey with redshifts ranging from z = 5.82 to z = 6.28. While the quasars above z = 6 showed a Gunn-Peterson trough, indicating that the IGM was still at least partly neutral, the ones below did not, meaning the hydrogen was ionized. As reionization is expected to occur over relatively short timescales, the results suggest that the universe was approaching the end of reionization at z = 6. This, in turn, suggests that the universe must still have been almost entirely neutral at z > 10. On the other hand, long absorption troughs persisting down to z < 5.5 in the Lyman-alpha and Lyman-beta forests suggest that reionization potentially extends later than z = 6.

CMB anisotropy and polarization

The anisotropy of the cosmic microwave background on different angular scales can also be used to study reionization. Photons undergo scattering when there are free electrons present, in a process known as Thomson scattering. However, as the universe expands, the density of free electrons will decrease, and scattering will occur less frequently. In the period during and after reionization, but before significant expansion had occurred to sufficiently lower the electron density, the light that composes the CMB will experience observable Thomson scattering. This scattering will leave its mark on the CMB anisotropy map, introducing secondary anisotropies (anisotropies introduced after recombination). The overall effect is to erase anisotropies that occur on smaller scales. While anisotropies on small scales are erased, polarization anisotropies are actually introduced because of reionization. By looking at the CMB anisotropies observed, and comparing with what they would look like had reionization not taken place, the electron column density at the time of reionization can be determined. With this, the age of the universe when reionization occurred can then be calculated.

The Wilkinson Microwave Anisotropy Probe allowed that comparison to be made. The initial observations, released in 2003, suggested that reionization took place from 30 > z > 11. This redshift range was in clear disagreement with the results from studying quasar spectra. However, the three year WMAP data returned a different result, with reionization beginning at z = 11 and the universe ionized by z = 7. This is in much better agreement with the quasar data.

Results in 2018 from Planck mission, yield an instantaneous reionization redshift of z = 7.68 ± 0.79.

The parameter usually quoted here is τ, the "optical depth to reionization," or alternatively, zre, the redshift of reionization, assuming it was an instantaneous event. While this is unlikely to be physical, since reionization was very likely not instantaneous, zre provides an estimate of the mean redshift of reionization.

Lyman alpha emission

Lyman alpha light from galaxies offers a complementary tool set to study reionization.  The Lyman alpha line is the n=2 to n=1 transition of neutral hydrogen, and can be produced copiously by galaxies with young stars. Moreover, Lyman alpha photons interact strongly with neutral hydrogen in intergalactic gas through resonant scattering, wherein neutral atoms in the ground (n=1) state absorb Lyman alpha photons and almost immediately re-emit them in a random direction. This obscures Lyman alpha emission from galaxies that are embedded in neutral gas. Thus, experiments to find galaxies by their Lyman alpha light can indicate the ionization state of the surrounding gas.  An average density of galaxies with detectable Lyman alpha emission means the surrounding gas must be ionized; while an absence of detectable Lyman alpha sources may indicate neutral regions.  A closely related class of experiments measures the Lyman alpha line strength in samples of galaxies identified by other methods (primarily Lyman break galaxy searches).

The earliest application of this method was in 2004, when the tension between late neutral gas indicated by quasar spectra and early reionization suggested by CMB results was strong.  The detection of Lyman alpha galaxies at redshift z=6.5 demonstrated that the intergalactic gas was already predominantly ionized at an earlier time than the quasar spectra suggested.  Subsequent applications of the method suggested some residual neutral gas as recently as z=6.5, but still indicate that a majority of intergalactic gas was ionized prior to z=7.

Lyman alpha emission can be used in other ways to further probe reionization. Theory suggests that reionization was patchy, meaning that the clustering of Lyman alpha selected samples should be strongly enhanced during the middle phases of reionization. Moreover, specific ionized regions can be pinpointed by identifying groups of Lyman alpha emitters.

21-cm line

Even with the quasar data roughly in agreement with the CMB anisotropy data, there are still a number of questions, especially concerning the energy sources of reionization and the effects on, and role of, structure formation during reionization. The 21-cm line in hydrogen is potentially a means of studying this period, as well as the "dark ages" that preceded reionization. The 21-cm line occurs in neutral hydrogen, due to differences in energy between the spin triplet and spin singlet states of the electron and proton. This transition is forbidden, meaning it occurs extremely rarely. The transition is also highly temperature dependent, meaning that as objects form in the "dark ages" and emit Lyman-alpha photons that are absorbed and re-emitted by surrounding neutral hydrogen, it will produce a 21-cm line signal in that hydrogen through Wouthuysen-Field coupling. By studying 21-cm line emission, it will be possible to learn more about the early structures that formed. Observations from the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) points to a signal from this era, although follow-up observations will be needed to confirm it. Several other projects hope to make headway in this area in the near future, such as the Precision Array for Probing the Epoch of Reionization (PAPER), Low Frequency Array (LOFAR), Murchison Widefield Array (MWA), Giant Metrewave Radio Telescope (GMRT), Mapper of the IGM Spin Temperature (MIST), the Dark Ages Radio Explorer (DARE) mission, and the Large-Aperture Experiment to Detect the Dark Ages (LEDA).

Energy sources

Astronomers hope to use observations such as this 2018 Hubble Space Telescope image to answer the question of how the Universe was reionised.

While observations have come in which narrow the window during which the epoch of reionization could have taken place, it is still uncertain which objects provided the photons that reionized the IGM. To ionize neutral hydrogen, an energy larger than 13.6 eV is required, which corresponds to photons with a wavelength of 91.2 nm or shorter. This is in the ultraviolet part of the electromagnetic spectrum, which means that the primary candidates are all sources which produce a significant amount of energy in the ultraviolet and above. How numerous the source is must also be considered, as well as the longevity, as protons and electrons will recombine if energy is not continuously provided to keep them apart. Altogether, the critical parameter for any source considered can be summarized as its "emission rate of hydrogen-ionizing photons per unit cosmological volume." With these constraints, it is expected that quasars and first generation stars and galaxies were the main sources of energy.

Dwarf galaxies

Dwarf galaxies are currently considered to be the primary source of ionizing photons during the epoch of reionization. For most scenarios, this would require the log-slope of the UV galaxy luminosity function, often denoted α, to be steeper than it is today, approaching α = -2. With the advent of the James Webb Space Telescope (JWST), constraints on the UV luminosity function at the Epoch of Reionization have become commonplace, allowing for better constraints on the faint, low-mass population of galaxies.

In 2014, two separate studies identified two Green Pea galaxies (GPs) to be likely Lyman Continuum (LyC)-emitting candidates. Compact dwarf star-forming galaxies like the GPs are considered excellent low-redshift analogs of high-redshift Lyman-alpha and LyC emitters (LAEs and LCEs, respectively). At that time, only two other LCEs were known: Haro 11 and Tololo-1247-232. Finding local LyC emitters has thus become crucial to the theories about the early universe and the epoch of reionization.

Subsequently, motivated, a series of surveys have been conducted using Hubble Space Telescope's Cosmic Origins Spectrograph (HST/COS) to measure the LyC directly. These efforts culminated in the Low-redshift Lyman Continuum Survey, a large HST/COS program which nearly tripled the number of direct measurements of the LyC from dwarf galaxies. To date, at least 50 LCEs have been confirmed using HST/COS with LyC escape fractions anywhere from ≈ 0 to 88%. The results from the Low-redshift Lyman Continuum Survey have provided the empirical foundation necessary to identify and understand LCEs at the Epoch of Reionization. With new observations from JWST, populations of LCEs are now being studied at cosmological redshifts greater than 6, allowing for the first time a detailed and direct assessment of the origins of cosmic Reionization. Combining these large samples of galaxies with new constraints on the UV luminosity function indicates that dwarf galaxies overwhelmingly contribute to Reionization.

Quasars

Quasars, a class of active galactic nuclei (AGN), were considered a good candidate source because they are highly efficient at converting mass to energy, and emit a great deal of light above the threshold for ionizing hydrogen. It is unknown, however, how many quasars existed prior to reionization. Only the brightest of quasars present during reionization can be detected, which means there is no direct information about dimmer quasars that existed. However, by looking at the more easily observed quasars in the nearby universe, and assuming that the luminosity function (number of quasars as a function of luminosity) during reionization will be approximately the same as it is today, it is possible to make estimates of the quasar populations at earlier times. Such studies have found that quasars do not exist in high enough numbers to reionize the IGM alone, saying that "only if the ionizing background is dominated by low-luminosity AGNs can the quasar luminosity function provide enough ionizing photons."

Population III stars

Simulated image of the first stars, 400 million years after the Big Bang.

Population III stars were the earliest stars, which had no elements more massive than hydrogen or helium. During Big Bang nucleosynthesis, the only elements that formed aside from hydrogen and helium were trace amounts of lithium. Yet quasar spectra have revealed the presence of heavy elements in the intergalactic medium at an early era. Supernova explosions produce such heavy elements, so hot, large, Population III stars which will form supernovae are a possible mechanism for reionization. While they have not been directly observed, they are consistent according to models using numerical simulation and current observations. A gravitationally lensed galaxy also provides indirect evidence of Population III stars. Even without direct observations of Population III stars, they are a compelling source. They are more efficient and effective ionizers than Population II stars, as they emit more ionizing photons, and are capable of reionizing hydrogen on their own in some reionization models with reasonable initial mass functions. As a consequence, Population III stars are currently considered the most likely energy source to initiate the reionization of the universe, though other sources are likely to have taken over and driven reionization to completion.

In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.

See also

Notes and references

  1. Furlanetto, Steven R.; Oh, S. Peng (July 2008). "The History and Morphology of Helium Reionization". The Astrophysical Journal. 681 (1): 1–17. arXiv:0711.1542. Bibcode:2008ApJ...681....1F. doi:10.1086/588546. ISSN 0004-637X.
  2. Gunn, J. E. & Peterson, B. A. (1965). "On the Density of Neutral Hydrogen in Intergalactic Space". The Astrophysical Journal. 142: 1633–1641. Bibcode:1965ApJ...142.1633G. doi:10.1086/148444.
  3. 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.
  4. Becker, George D.; Bolton, James S.; Madau, Piero; Pettini, Max; Ryan-Weber, Emma V.; Venemans, Bram P. (2015-03-11). "Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six". Monthly Notices of the Royal Astronomical Society. 447 (4): 3402–3419. arXiv:1407.4850. doi:10.1093/mnras/stu2646. ISSN 1365-2966.
  5. Zhu, Yongda; Becker, George D.; Bosman, Sarah E. I.; Keating, Laura C.; D’Odorico, Valentina; Davies, Rebecca L.; Christenson, Holly M.; Bañados, Eduardo; Bian, Fuyan; Bischetti, Manuela; Chen, Huanqing; Davies, Frederick B.; Eilers, Anna-Christina; Fan, Xiaohui; Gaikwad, Prakash (2022-06-01). "Long Dark Gaps in the Lyβ Forest at z < 6: Evidence of Ultra-late Reionization from XQR-30 Spectra". The Astrophysical Journal. 932 (2): 76. arXiv:2205.04569. Bibcode:2022ApJ...932...76Z. doi:10.3847/1538-4357/ac6e60. ISSN 0004-637X.
  6. Kaplinghat, Manoj; et al. (2003). "Probing the Reionization History of the universe using the Cosmic Microwave Background Polarization". The Astrophysical Journal. 583 (1): 24–32. arXiv:astro-ph/0207591. Bibcode:2003ApJ...583...24K. doi:10.1086/344927. S2CID 11253251.
  7. Dore, O.; et al. (2007). "Signature of patchy reionization in the polarization anisotropy of the CMB". Physical Review D. 76 (4): 043002. arXiv:astro-ph/0701784. Bibcode:2007PhRvD..76d3002D. doi:10.1103/PhysRevD.76.043002. S2CID 119360903.
  8. Kogut, A.; et al. (2003). "First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature-Polarization Correlation". The Astrophysical Journal Supplement Series. 148 (1): 161–173. arXiv:astro-ph/0302213. Bibcode:2003ApJS..148..161K. doi:10.1086/377219. S2CID 15253442.
  9. Spergel, D. N.; et al. (2007). "Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology". The Astrophysical Journal Supplement Series. 170 (2): 377–408. arXiv:astro-ph/0603449. Bibcode:2007ApJS..170..377S. doi:10.1086/513700. S2CID 1386346.
  10. Planck Collaboration (2020). "Planck 2018 results. VI. Cosmological parameters". Astronomy & Astrophysics. 641: A6. arXiv:1807.06209. Bibcode:2020A&A...641A...6P. doi:10.1051/0004-6361/201833910. S2CID 119335614.
  11. Partridge, R. B.; Peebles, P. J. E. (March 1967). "Are Young Galaxies Visible?". The Astrophysical Journal. 147: 868. Bibcode:1967ApJ...147..868P. doi:10.1086/149079. ISSN 0004-637X.
  12. Miralda-Escude, Jordi; Rees, Martin J. (1998-04-10). "Searching for the Earliest Galaxies Using the Gunn-Peterson Trough and the Lyα Emission Line". The Astrophysical Journal. 497 (1): 21–27. arXiv:astro-ph/9707193. Bibcode:1998ApJ...497...21M. doi:10.1086/305458. ISSN 0004-637X.
  13. Stark, Daniel P.; Ellis, Richard S.; Chiu, Kuenley; Ouchi, Masami; Bunker, Andrew (2010-11-01). "Keck spectroscopy of faint 3 < z < 7 Lyman break galaxies - I. New constraints on cosmic reionization from the luminosity and redshift-dependent fraction of Lyman α emission: The Lyα emitting fraction at high redshift". Monthly Notices of the Royal Astronomical Society. 408 (3): 1628–1648. arXiv:1003.5244. doi:10.1111/j.1365-2966.2010.17227.x.
  14. Pentericci, L.; Fontana, A.; Vanzella, E.; Castellano, M.; Grazian, A.; Dijkstra, M.; Boutsia, K.; Cristiani, S.; Dickinson, M.; Giallongo, E.; Giavalisco, M.; Maiolino, R.; Moorwood, A.; Paris, D.; Santini, P. (2011-12-20). "SPECTROSCOPIC CONFIRMATION OF z ∼ 7 LYMAN BREAK GALAXIES: PROBING THE EARLIEST GALAXIES AND THE EPOCH OF REIONIZATION". The Astrophysical Journal. 743 (2): 132. arXiv:1107.1376. Bibcode:2011ApJ...743..132P. doi:10.1088/0004-637X/743/2/132. ISSN 0004-637X.
  15. Tilvi, V.; Papovich, C.; Finkelstein, S. L.; Long, J.; Song, M.; Dickinson, M.; Ferguson, H. C.; Koekemoer, A. M.; Giavalisco, M.; Mobasher, B. (2014-09-17). "RAPID DECLINE OF Lyα EMISSION TOWARD THE REIONIZATION ERA". The Astrophysical Journal. 794 (1): 5. arXiv:1405.4869. Bibcode:2014ApJ...794....5T. doi:10.1088/0004-637X/794/1/5. ISSN 1538-4357.
  16. Malhotra, Sangeeta; Rhoads, James E. (2004-12-10). "Luminosity Functions of Lyα Emitters at Redshifts z = 6.5 and z = 5.7: Evidence against Reionization at z ≤ 6.5". The Astrophysical Journal. 617 (1): L5–L8. arXiv:astro-ph/0407408. Bibcode:2004ApJ...617L...5M. doi:10.1086/427182. ISSN 0004-637X.
  17. Hu, E. M.; Cowie, L. L.; Barger, A. J.; Capak, P.; Kakazu, Y.; Trouille, L. (2010-12-10). "AN ATLAS OF z = 5.7 AND z = 6.5 Lyα EMITTERS". The Astrophysical Journal. 725 (1): 394–423. arXiv:1009.1144. Bibcode:2010ApJ...725..394H. doi:10.1088/0004-637X/725/1/394. ISSN 0004-637X.
  18. Kashikawa, Nobunari; Shimasaku, Kazuhiro; Matsuda, Yuichi; Egami, Eiichi; Jiang, Linhua; Nagao, Tohru; Ouchi, Masami; Malkan, Matthew A.; Hattori, Takashi; Ota, Kazuaki; Taniguchi, Yoshiaki; Okamura, Sadanori; Ly, Chun; Iye, Masanori; Furusawa, Hisanori (2011-06-20). "COMPLETING THE CENSUS OF Lyα EMITTERS AT THE REIONIZATION EPOCH $^,$". The Astrophysical Journal. 734 (2): 119. arXiv:1104.2330. Bibcode:2011ApJ...734..119K. doi:10.1088/0004-637X/734/2/119. ISSN 0004-637X.
  19. Ouchi, Masami; Shimasaku, Kazuhiro; Furusawa, Hisanori; Saito, Tomoki; Yoshida, Makiko; Akiyama, Masayuki; Ono, Yoshiaki; Yamada, Toru; Ota, Kazuaki; Kashikawa, Nobunari; Iye, Masanori; Kodama, Tadayuki; Okamura, Sadanori; Simpson, Chris; Yoshida, Michitoshi (2010-11-01). "STATISTICS OF 207 Lyα EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS". The Astrophysical Journal. 723 (1): 869–894. arXiv:1007.2961. Bibcode:2010ApJ...723..869O. doi:10.1088/0004-637X/723/1/869. ISSN 0004-637X.
  20. Wold, Isak G. B.; Malhotra, Sangeeta; Rhoads, James; Wang, Junxian; Hu, Weida; Perez, Lucia A.; Zheng, Zhen-Ya; Khostovan, Ali Ahmad; Walker, Alistair R.; Barrientos, L. Felipe; González-López, Jorge; Harish, Santosh; Infante, Leopoldo; Jiang, Chunyan; Pharo, John (2022-03-01). "LAGER Lyα Luminosity Function at z ∼ 7: Implications for Reionization". The Astrophysical Journal. 927 (1): 36. arXiv:2105.12191. Bibcode:2022ApJ...927...36W. doi:10.3847/1538-4357/ac4997. ISSN 0004-637X.
  21. McQuinn, Matthew; Hernquist, Lars; Zaldarriaga, Matias; Dutta, Suvendra (October 2007). "Studying reionization with Lyα emitters". Monthly Notices of the Royal Astronomical Society. 381 (1): 75–96. arXiv:0704.2239. Bibcode:2007MNRAS.381...75M. doi:10.1111/j.1365-2966.2007.12085.x. ISSN 0035-8711.
  22. Tilvi, V.; Malhotra, S.; Rhoads, J. E.; Coughlin, A.; Zheng, Z.; Finkelstein, S. L.; Veilleux, S.; Mobasher, B.; Wang, J.; Probst, R.; Swaters, R.; Hibon, P.; Joshi, B.; Zabl, J.; Jiang, T. (2020-03-01). "Onset of Cosmic Reionization: Evidence of an Ionized Bubble Merely 680 Myr after the Big Bang". The Astrophysical Journal Letters. 891 (1): L10. arXiv:2001.00873. Bibcode:2020ApJ...891L..10T. doi:10.3847/2041-8213/ab75ec. ISSN 2041-8205.
  23. Hu, Weida; Wang, Junxian; Infante, Leopoldo; Rhoads, James E.; Zheng, Zhen-Ya; Yang, Huan; Malhotra, Sangeeta; Barrientos, L. Felipe; Jiang, Chunyan; González-López, Jorge; Prieto, Gonzalo; Perez, Lucia A.; Hibon, Pascale; Galaz, Gaspar; Coughlin, Alicia (2021-01-25). "A Lyman-α protocluster at redshift 6.9". Nature Astronomy. 5 (5): 485–490. arXiv:2101.10204. Bibcode:2021NatAs...5..485H. doi:10.1038/s41550-020-01291-y. ISSN 2397-3366.
  24. Barkana, Rennan & Loeb, Abraham (2005). "Detecting the Earliest Galaxies through Two New Sources of 21 Centimeter Fluctuations". The Astrophysical Journal. 626 (1): 1–11. arXiv:astro-ph/0410129. Bibcode:2005ApJ...626....1B. doi:10.1086/429954. S2CID 7343629.
  25. Alvarez, M. A.; Pen, Ue-Li; Chang, Tzu-Ching (2010). "Enhanced Detectability of Pre-reionization 21 cm Structure". The Astrophysical Journal Letters. 723 (1): L17–L21. arXiv:1007.0001. Bibcode:2010ApJ...723L..17A. doi:10.1088/2041-8205/723/1/L17. S2CID 118436837.
  26. "Astronomers detect light from the Universe's first stars". 28 February 2018. Retrieved 1 March 2018.
  27. "Hubble opens its eye again". www.spacetelescope.org. Retrieved 17 December 2018.
  28. ^ Madau, Piero; et al. (1999). "Radiative Transfer in a Clumpy Universe. III. The Nature of Cosmological Ionizing Source". The Astrophysical Journal. 514 (2): 648–659. arXiv:astro-ph/9809058. Bibcode:1999ApJ...514..648M. doi:10.1086/306975. S2CID 17932350.
  29. Barkana, R.; Loeb, A. (2001). "In the Beginning: The First Sources of Light and the Reionization of the Universe". Physics Reports. 349 (2): 125–238. arXiv:astro-ph/0010468. Bibcode:2001PhR...349..125B. doi:10.1016/S0370-1573(01)00019-9. S2CID 119094218.
  30. ^ Bouwens, R. J.; et al. (2012). "Lower-luminosity Galaxies Could Reionize the Universe: Very Steep Faint-end Slopes to the UV Luminosity Functions at z >= 5-8 from the HUDF09 WFC3/IR Observations". The Astrophysical Journal Letters. 752 (1): L5. arXiv:1105.2038. Bibcode:2012ApJ...752L...5B. doi:10.1088/2041-8205/752/1/L5. S2CID 118856513.
  31. Atek, Hakim; Richard, Johan; Jauzac, Mathilde; Kneib, Jean-Paul; Natarajan, Priyamvada; Limousin, Marceau; Schaerer, Daniel; Jullo, Eric; Ebeling, Harald; Egami, Eiichi; Clement, Benjamin (2015-11-18). "Are ultra-faint galaxies at z = 6–8 responsible for cosmic reionization? Combined constraints from the Hubble frontier fields clusters and parallels". The Astrophysical Journal. 814 (1): 69. arXiv:1509.06764. Bibcode:2015ApJ...814...69A. doi:10.1088/0004-637X/814/1/69. ISSN 1538-4357. S2CID 73567045.
  32. Harikane, Yuichi; Ouchi, Masami; Oguri, Masamune; Ono, Yoshiaki; Nakajima, Kimihiko; Isobe, Yuki; Umeda, Hiroya; Mawatari, Ken; Zhang, Yechi (2023-03-01). "A Comprehensive Study of Galaxies at z ∼ 9–16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch". The Astrophysical Journal Supplement Series. 265 (1): 5. arXiv:2208.01612. Bibcode:2023ApJS..265....5H. doi:10.3847/1538-4365/acaaa9. ISSN 0067-0049.
  33. McLeod, D. J.; Donnan, C. T.; McLure, R. J.; Dunlop, J. S.; Magee, D.; Begley, R.; Carnall, A. C.; Cullen, F.; Ellis, R. S.; Hamadouche, M. L.; Stanton, T. M. (2023). "The galaxy UV luminosity function at z ≃ 11 from a suite of public JWST ERS, ERO and Cycle-1 programs". Monthly Notices of the Royal Astronomical Society. 527 (3): 5004. arXiv:2304.14469. Bibcode:2024MNRAS.527.5004M. doi:10.1093/mnras/stad3471.
  34. ^ Jaskot, A. E. & Oey, M. S. (2014). "Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth". The Astrophysical Journal Letters. 791 (2): L19. arXiv:1406.4413. Bibcode:2014ApJ...791L..19J. doi:10.1088/2041-8205/791/2/L19. S2CID 119294145.
  35. ^ Verhamme, A.; Orlitova, I.; Schaerer, D.; Hayes, M. (2014). "On the use of Lyman-alpha to detect Lyman continuum leaking galaxies". arXiv:1404.2958v1 .
  36. Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Henkel, C.; Schaerer, D.; Thuan, T. X. (February 2021). "Low-redshift compact star-forming galaxies as analogues of high-redshift star-forming galaxies". Astronomy & Astrophysics. 646: A138. arXiv:2103.01505. Bibcode:2021A&A...646A.138I. doi:10.1051/0004-6361/202039772. ISSN 0004-6361. S2CID 232092358.
  37. Nakajima, K. & Ouchi, M. (2014). "Ionization state of inter-stellar medium in galaxies: evolution, SFR-M*-Z dependence, and ionizing photon escape". Monthly Notices of the Royal Astronomical Society. 442 (1): 900–916. arXiv:1309.0207. Bibcode:2014MNRAS.442..900N. doi:10.1093/mnras/stu902. S2CID 118617426.
  38. Izotov, Y. I.; Orlitová, I.; Schaerer, D.; Thuan, T. X.; Verhamme, A.; Guseva, N. G.; Worseck, G. (2016-01-14). "Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy". Nature. 529 (7585): 178–180. arXiv:1601.03068. Bibcode:2016Natur.529..178I. doi:10.1038/nature16456. ISSN 0028-0836. PMID 26762455. S2CID 3033749.
  39. Izotov, Y. I.; Schaerer, D.; Thuan, T. X.; Worseck, G.; Guseva, N. G.; Orlitová, I.; Verhamme, A. (2016-10-01). "Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies". Monthly Notices of the Royal Astronomical Society. 461 (4): 3683–3701. arXiv:1605.05160. doi:10.1093/mnras/stw1205. ISSN 0035-8711.
  40. Izotov, Y. I.; Schaerer, D.; Worseck, G.; Guseva, N. G.; Thuan, T. X.; Verhamme, A.; Orlitová, I.; Fricke, K. J. (2018-03-11). "J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons". Monthly Notices of the Royal Astronomical Society. 474 (4): 4514–4527. arXiv:1711.11449. doi:10.1093/mnras/stx3115. ISSN 0035-8711.
  41. Izotov, Y. I.; Worseck, G.; Schaerer, D.; Guseva, N. G; Thuan, T. X.; Fricke; Verhamme, A.; Orlitová, I. (2018-08-21). "Low-redshift Lyman continuum leaking galaxies with high [O iii]/[O ii] ratios". Monthly Notices of the Royal Astronomical Society. 478 (4): 4851–4865. arXiv:1805.09865. doi:10.1093/mnras/sty1378. ISSN 0035-8711.
  42. Wang, Bingjie; Heckman, Timothy M.; Leitherer, Claus; Alexandroff, Rachel; Borthakur, Sanchayeeta; Overzier, Roderik A. (2019-10-30). "A New Technique for Finding Galaxies Leaking Lyman-continuum Radiation: [S ii]-deficiency". The Astrophysical Journal. 885 (1): 57. arXiv:1909.01368. Bibcode:2019ApJ...885...57W. doi:10.3847/1538-4357/ab418f. ISSN 1538-4357.
  43. Izotov, Y. I.; Worseck, G.; Schaerer, D.; Guseva, N. G.; Chisholm, J.; Thuan, T. X.; Fricke, K. J.; Verhamme, A. (2021-03-22). "Lyman continuum leakage from low-mass galaxies with M ⋆ < 108 M⊙". Monthly Notices of the Royal Astronomical Society. 503 (2): 1734–1752. arXiv:2103.01514. doi:10.1093/mnras/stab612. ISSN 0035-8711.
  44. ^ Flury, Sophia R.; Jaskot, Anne E.; Ferguson, Harry C.; Worseck, Gábor; Makan, Kirill; Chisholm, John; Saldana-Lopez, Alberto; Schaerer, Daniel; McCandliss, Stephan; Wang, Bingjie; Ford, N. M.; Heckman, Timothy; Ji, Zhiyuan; Giavalisco, Mauro; Amorin, Ricardo (2022-05-01). "The Low-redshift Lyman Continuum Survey. I. New, Diverse Local Lyman Continuum Emitters". The Astrophysical Journal Supplement Series. 260 (1): 1. arXiv:2201.11716. Bibcode:2022ApJS..260....1F. doi:10.3847/1538-4365/ac5331. ISSN 0067-0049.
  45. Saldana-Lopez, Alberto; Schaerer, Daniel; Chisholm, John; Flury, Sophia R.; Jaskot, Anne E.; Worseck, Gábor; Makan, Kirill; Gazagnes, Simon; Mauerhofer, Valentin; Verhamme, Anne; Amorín, Ricardo O.; Ferguson, Harry C.; Giavalisco, Mauro; Grazian, Andrea; Hayes, Matthew J. (July 2022). "The Low-Redshift Lyman Continuum Survey: Unveiling the ISM properties of low- z Lyman-continuum emitters". Astronomy & Astrophysics. 663: A59. arXiv:2201.11800. Bibcode:2022A&A...663A..59S. doi:10.1051/0004-6361/202141864. ISSN 0004-6361. S2CID 246411216.
  46. Flury, Sophia R.; Jaskot, Anne E.; Ferguson, Harry C.; Worseck, Gábor; Makan, Kirill; Chisholm, John; Saldana-Lopez, Alberto; Schaerer, Daniel; McCandliss, Stephan R.; Xu, Xinfeng; Wang, Bingjie; Oey, M. S.; Ford, N. M.; Heckman, Timothy; Ji, Zhiyuan (2022-05-01). "The Low-redshift Lyman Continuum Survey. II. New Insights into LyC Diagnostics". The Astrophysical Journal. 930 (2): 126. arXiv:2203.15649. Bibcode:2022ApJ...930..126F. doi:10.3847/1538-4357/ac61e4. ISSN 0004-637X.
  47. Chisholm, J.; Saldana-Lopez, A.; Flury, S.; Schaerer, D.; Jaskot, A.; Amorín, R.; Atek, H.; Finkelstein, S. L.; Fleming, B.; Ferguson, H.; Fernández, V.; Giavalisco, M.; Hayes, M.; Heckman, T.; Henry, A. (2022-11-09). "The far-ultraviolet continuum slope as a Lyman Continuum escape estimator at high redshift". Monthly Notices of the Royal Astronomical Society. 517 (4): 5104–5120. arXiv:2207.05771. doi:10.1093/mnras/stac2874. ISSN 0035-8711.
  48. Mascia, S.; Pentericci, L.; Calabrò, A.; Treu, T.; Santini, P.; Yang, L.; Napolitano, L.; Roberts-Borsani, G.; Bergamini, P.; Grillo, C.; Rosati, P.; Vulcani, B.; Castellano, M.; Boyett, K.; Fontana, A. (April 2023). "Closing in on the sources of cosmic reionization: First results from the GLASS-JWST program". Astronomy & Astrophysics. 672: A155. arXiv:2301.02816. Bibcode:2023A&A...672A.155M. doi:10.1051/0004-6361/202345866. ISSN 0004-6361. S2CID 255546596.
  49. Mascia, S.; Pentericci, L.; Calabrò, A.; Santini, P.; Napolitano, L.; Haro, P. Arrabal; Castellano, M.; Dickinson, M.; Ocvirk, P.; Lewis, J. S. W.; Amorín, R.; Bagley, M.; Cleri, R. N. J.; Costantin, L.; Dekel, A. (2024). "New insight on the nature of cosmic reionizers from the CEERS survey". Astronomy and Astrophysics. 685: A3. arXiv:2309.02219. Bibcode:2024A&A...685A...3M. doi:10.1051/0004-6361/202347884.
  50. Shapiro, Paul & Giroux, Mark (1987). "Cosmological H II regions and the photoionization of the intergalactic medium". The Astrophysical Journal. 321: 107–112. Bibcode:1987ApJ...321L.107S. doi:10.1086/185015.
  51. Fan, Xiaohu; et al. (2001). "A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6". The Astronomical Journal. 122 (6): 2833–2849. arXiv:astro-ph/0108063. Bibcode:2001AJ....122.2833F. doi:10.1086/324111. S2CID 119339804.
  52. Gnedin, Nickolay & Ostriker, Jeremiah (1997). "Reionization of the Universe and the Early Production of Metals". Astrophysical Journal. 486 (2): 581–598. arXiv:astro-ph/9612127. Bibcode:1997ApJ...486..581G. doi:10.1086/304548. S2CID 5758398.
  53. Limin Lu; et al. (1998). "The Metal Contents of Very Low Column Density Lyman-alpha Clouds: Implications for the Origin of Heavy Elements in the Intergalactic Medium". arXiv:astro-ph/9802189.
  54. Fosbury, R. A. E.; et al. (2003). "Massive Star Formation in a Gravitationally Lensed H II Galaxy at z = 3.357". Astrophysical Journal. 596 (1): 797–809. arXiv:astro-ph/0307162. Bibcode:2003ApJ...596..797F. doi:10.1086/378228. S2CID 17808828.
  55. Tumlinson, Jason; et al. (2002). "Cosmological Reionization by the First Stars: Evolving Spectra of Population III". ASP Conference Proceedings. 267: 433–434. Bibcode:2002ASPC..267..433T.
  56. Venkatesan, Apama; et al. (2003). "Evolving Spectra of Population III Stars: Consequences for Cosmological Reionization". Astrophysical Journal. 584 (2): 621–632. arXiv:astro-ph/0206390. Bibcode:2003ApJ...584..621V. doi:10.1086/345738. S2CID 17737785.
  57. Alvarez, Marcelo; et al. (2006). "The H II Region of the First Star". Astrophysical Journal. 639 (2): 621–632. arXiv:astro-ph/0507684. Bibcode:2006ApJ...639..621A. doi:10.1086/499578. S2CID 12753436.
  58. Sobral, David; Matthee, Jorryt; Darvish, Behnam; Schaerer, Daniel; Mobasher, Bahram; Röttgering, Huub J. A.; Santos, Sérgio; Hemmati, Shoubaneh (4 June 2015). "Evidence For POPIII-Like Stellar Populations In The Most Luminous LYMAN-α Emitters At The Epoch Of Re-Ionisation: Spectroscopic Confirmation". The Astrophysical Journal. 808 (2): 139. arXiv:1504.01734. Bibcode:2015ApJ...808..139S. doi:10.1088/0004-637x/808/2/139. S2CID 18471887.
  59. Overbye, Dennis (17 June 2015). "Astronomers Report Finding Earliest Stars That Enriched Cosmos". The New York Times. Retrieved 17 June 2015.

External links

Timeline of the Big Bang
Chronology of the universe
Fate of the universe
Cosmology
Background
History of
cosmological theories
Past universe
Present universe
Future universe
Components
Structure formation
Experiments
astronomy portal
Portal: Categories: