Editing Reionization (section)

=== Dwarf galaxies ===
[[Dwarf galaxies]] are currently considered to be the primary source of ionizing photons during the epoch of reionization.<ref name="Bouwens_LLG">{{cite journal |author=Bouwens |first=R. J. |display-authors=etal |date=2012 |title=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 |journal=The Astrophysical Journal Letters |volume=752 |issue=1 |pages=L5 |arxiv=1105.2038 |bibcode=2012ApJ...752L...5B |doi=10.1088/2041-8205/752/1/L5 |s2cid=118856513}}</ref><ref>{{Cite journal |last1=Atek |first1=Hakim |last2=Richard |first2=Johan |last3=Jauzac |first3=Mathilde |last4=Kneib |first4=Jean-Paul |last5=Natarajan |first5=Priyamvada |last6=Limousin |first6=Marceau |last7=Schaerer |first7=Daniel |last8=Jullo |first8=Eric |last9=Ebeling |first9=Harald |last10=Egami |first10=Eiichi |last11=Clement |first11=Benjamin |date=2015-11-18 |title=Are ultra-faint galaxies at z = 6–8 responsible for cosmic reionization? Combined constraints from the Hubble frontier fields clusters and parallels |url=https://iopscience.iop.org/article/10.1088/0004-637X/814/1/69 |journal=The Astrophysical Journal |volume=814 |issue=1 |pages=69 |doi=10.1088/0004-637X/814/1/69 |arxiv=1509.06764 |bibcode=2015ApJ...814...69A |s2cid=73567045 |issn=1538-4357}}</ref> For most scenarios, this would require the log-slope of the UV galaxy [[Luminosity function (astronomy)|luminosity function]], often denoted α, to be steeper than it is today, approaching α = -2.<ref name=Bouwens_LLG/> With the advent of the ''James Webb Space Telescope'' (JWST), constraints on the UV luminosity function at the Epoch of Reionization have become commonplace,<ref>{{Cite journal |last1=Harikane |first1=Yuichi |last2=Ouchi |first2=Masami |last3=Oguri |first3=Masamune |last4=Ono |first4=Yoshiaki |last5=Nakajima |first5=Kimihiko |last6=Isobe |first6=Yuki |last7=Umeda |first7=Hiroya |last8=Mawatari |first8=Ken |last9=Zhang |first9=Yechi |date=2023-03-01 |title=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 |journal=The Astrophysical Journal Supplement Series |volume=265 |issue=1 |pages=5 |doi=10.3847/1538-4365/acaaa9 |arxiv=2208.01612 |bibcode=2023ApJS..265....5H |issn=0067-0049 |doi-access=free }}</ref><ref>{{Cite journal |last1=McLeod |first1=D. J. |last2=Donnan |first2=C. T. |last3=McLure |first3=R. J. |last4=Dunlop |first4=J. S. |last5=Magee |first5=D. |last6=Begley |first6=R. |last7=Carnall |first7=A. C. |last8=Cullen |first8=F. |last9=Ellis |first9=R. S. |last10=Hamadouche |first10=M. L. |last11=Stanton |first11=T. M. |date=2023 |title=The galaxy UV luminosity function at z ≃ 11 from a suite of public JWST ERS, ERO and Cycle-1 programs |journal=Monthly Notices of the Royal Astronomical Society |volume=527 |issue=3 |page=5004 |doi=10.1093/mnras/stad3471 |doi-access=free |arxiv=2304.14469|bibcode=2024MNRAS.527.5004M }}</ref> allowing for better constraints on the faint, low-mass population of galaxies.

In 2014, two separate studies identified two [[Pea galaxy|Green Pea galaxies]] (GPs) to be likely [[Lyc photon|Lyman Continuum]] (LyC)-emitting candidates.<ref name="Jaskot_2014(b)">{{cite journal |author=Jaskot |first1=A. E. |last2=Oey |first2=M. S. |name-list-style=amp |date=2014 |title=Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth |journal=The Astrophysical Journal Letters |volume=791 |issue=2 |pages=L19 |arxiv=1406.4413 |bibcode=2014ApJ...791L..19J |doi=10.1088/2041-8205/791/2/L19 |s2cid=119294145}}</ref><ref name=Verhamme_2014>{{cite arXiv |first1=A. | last1=Verhamme |first2=I. | last2=Orlitova |first3=D. | last3=Schaerer|first4=M. | last4=Hayes |title=On the use of Lyman-alpha to detect Lyman continuum leaking galaxies| date=2014| class=astro-ph.GA |eprint=1404.2958v1 }}</ref> 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).<ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Guseva |first2=N. G. |last3=Fricke |first3=K. J. |last4=Henkel |first4=C. |last5=Schaerer |first5=D. |last6=Thuan |first6=T. X. |date=February 2021 |title=Low-redshift compact star-forming galaxies as analogues of high-redshift star-forming galaxies |url=https://www.aanda.org/10.1051/0004-6361/202039772 |journal=Astronomy & Astrophysics |volume=646 |pages=A138 |doi=10.1051/0004-6361/202039772 |arxiv=2103.01505 |bibcode=2021A&A...646A.138I |s2cid=232092358 |issn=0004-6361}}</ref> At that time, only two other LCEs were known: [[Haro 11]] and [[Tololo-1247-232]].<ref name=Jaskot_2014(b)/><ref name=Verhamme_2014/><ref name="nakajima">{{cite journal |author=Nakajima |first1=K. |last2=Ouchi |first2=M. |name-list-style=amp |date=2014 |title=Ionization state of inter-stellar medium in galaxies: evolution, SFR-M*-Z dependence, and ionizing photon escape |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=442 |issue=1 |pages=900–916 |arxiv=1309.0207 |bibcode=2014MNRAS.442..900N |doi=10.1093/mnras/stu902 |doi-access=free |s2cid=118617426}}</ref> Finding local LyC emitters has thus become crucial to the theories about the early universe and the epoch of reionization.<ref name=Jaskot_2014(b)/><ref name=Verhamme_2014/>

Subsequently, motivated, a series of surveys have been conducted using ''Hubble Space Telescope''<nowiki/>'s Cosmic Origins Spectrograph (''HST''/COS) to measure the LyC directly.<ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Orlitová |first2=I. |last3=Schaerer |first3=D. |last4=Thuan |first4=T. X. |last5=Verhamme |first5=A. |last6=Guseva |first6=N. G. |last7=Worseck |first7=G. |date=2016-01-14 |title=Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy |url=https://www.nature.com/articles/nature16456 |journal=Nature |language=en |volume=529 |issue=7585 |pages=178–180 |doi=10.1038/nature16456 |pmid=26762455 |arxiv=1601.03068 |bibcode=2016Natur.529..178I |s2cid=3033749 |issn=0028-0836}}</ref><ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Schaerer |first2=D. |last3=Thuan |first3=T. X. |last4=Worseck |first4=G. |last5=Guseva |first5=N. G. |last6=Orlitová |first6=I. |last7=Verhamme |first7=A. |date=2016-10-01 |title=Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=461 |issue=4 |pages=3683–3701 |doi=10.1093/mnras/stw1205 |issn=0035-8711|doi-access=free |arxiv=1605.05160 }}</ref><ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Schaerer |first2=D. |last3=Worseck |first3=G. |last4=Guseva |first4=N. G. |last5=Thuan |first5=T. X. |last6=Verhamme |first6=A. |last7=Orlitová |first7=I. |last8=Fricke |first8=K. J. |date=2018-03-11 |title=J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons |url=http://academic.oup.com/mnras/article/474/4/4514/4683272 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=474 |issue=4 |pages=4514–4527 |doi=10.1093/mnras/stx3115 |issn=0035-8711|doi-access=free |arxiv=1711.11449 }}</ref><ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Worseck |first2=G. |last3=Schaerer |first3=D. |last4=Guseva |first4=N. G |last5=Thuan |first5=T. X. |last6=Fricke |last7=Verhamme |first7=A. |last8=Orlitová |first8=I. |date=2018-08-21 |title=Low-redshift Lyman continuum leaking galaxies with high [O iii]/[O ii] ratios |url=https://academic.oup.com/mnras/article/478/4/4851/5004866 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=478 |issue=4 |pages=4851–4865 |doi=10.1093/mnras/sty1378 |issn=0035-8711|doi-access=free |arxiv=1805.09865 }}</ref><ref>{{Cite journal |last1=Wang |first1=Bingjie |last2=Heckman |first2=Timothy M. |last3=Leitherer |first3=Claus |last4=Alexandroff |first4=Rachel |last5=Borthakur |first5=Sanchayeeta |last6=Overzier |first6=Roderik A. |date=2019-10-30 |title=A New Technique for Finding Galaxies Leaking Lyman-continuum Radiation: [S ii]-deficiency |journal=The Astrophysical Journal |volume=885 |issue=1 |pages=57 |doi=10.3847/1538-4357/ab418f |arxiv=1909.01368 |bibcode=2019ApJ...885...57W |issn=1538-4357 |doi-access=free }}</ref><ref>{{Cite journal |last1=Izotov |first1=Y. I. |last2=Worseck |first2=G. |last3=Schaerer |first3=D. |last4=Guseva |first4=N. G. |last5=Chisholm |first5=J. |last6=Thuan |first6=T. X. |last7=Fricke |first7=K. J. |last8=Verhamme |first8=A. |date=2021-03-22 |title=Lyman continuum leakage from low-mass galaxies with M ⋆ &lt; 108 M⊙ |url=https://academic.oup.com/mnras/article/503/2/1734/6157755 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=503 |issue=2 |pages=1734–1752 |doi=10.1093/mnras/stab612 |doi-access=free |issn=0035-8711|arxiv=2103.01514 }}</ref> These efforts culminated in the Low-redshift Lyman Continuum Survey,<ref name=":0">{{Cite journal |last1=Flury |first1=Sophia R. |last2=Jaskot |first2=Anne E. |last3=Ferguson |first3=Harry C. |last4=Worseck |first4=Gábor |last5=Makan |first5=Kirill |last6=Chisholm |first6=John |last7=Saldana-Lopez |first7=Alberto |last8=Schaerer |first8=Daniel |last9=McCandliss |first9=Stephan |last10=Wang |first10=Bingjie |last11=Ford |first11=N. M. |last12=Heckman |first12=Timothy |last13=Ji |first13=Zhiyuan |last14=Giavalisco |first14=Mauro |last15=Amorin |first15=Ricardo |date=2022-05-01 |title=The Low-redshift Lyman Continuum Survey. I. New, Diverse Local Lyman Continuum Emitters |journal=The Astrophysical Journal Supplement Series |volume=260 |issue=1 |pages=1 |doi=10.3847/1538-4365/ac5331 |arxiv=2201.11716 |bibcode=2022ApJS..260....1F |issn=0067-0049 |doi-access=free }}</ref> 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<ref name=":0" /> 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.<ref>{{Cite journal |last1=Saldana-Lopez |first1=Alberto |last2=Schaerer |first2=Daniel |last3=Chisholm |first3=John |last4=Flury |first4=Sophia R. |last5=Jaskot |first5=Anne E. |last6=Worseck |first6=Gábor |last7=Makan |first7=Kirill |last8=Gazagnes |first8=Simon |last9=Mauerhofer |first9=Valentin |last10=Verhamme |first10=Anne |last11=Amorín |first11=Ricardo O. |last12=Ferguson |first12=Harry C. |last13=Giavalisco |first13=Mauro |last14=Grazian |first14=Andrea |last15=Hayes |first15=Matthew J. |date=July 2022 |title=The Low-Redshift Lyman Continuum Survey: Unveiling the ISM properties of low- z Lyman-continuum emitters |url=https://www.aanda.org/10.1051/0004-6361/202141864 |journal=Astronomy & Astrophysics |volume=663 |pages=A59 |doi=10.1051/0004-6361/202141864 |arxiv=2201.11800 |bibcode=2022A&A...663A..59S |s2cid=246411216 |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Flury |first1=Sophia R. |last2=Jaskot |first2=Anne E. |last3=Ferguson |first3=Harry C. |last4=Worseck |first4=Gábor |last5=Makan |first5=Kirill |last6=Chisholm |first6=John |last7=Saldana-Lopez |first7=Alberto |last8=Schaerer |first8=Daniel |last9=McCandliss |first9=Stephan R. |last10=Xu |first10=Xinfeng |last11=Wang |first11=Bingjie |last12=Oey |first12=M. S. |last13=Ford |first13=N. M. |last14=Heckman |first14=Timothy |last15=Ji |first15=Zhiyuan |date=2022-05-01 |title=The Low-redshift Lyman Continuum Survey. II. New Insights into LyC Diagnostics |journal=The Astrophysical Journal |volume=930 |issue=2 |pages=126 |doi=10.3847/1538-4357/ac61e4 |arxiv=2203.15649 |bibcode=2022ApJ...930..126F |issn=0004-637X |doi-access=free }}</ref><ref>{{Cite journal |last1=Chisholm |first1=J. |last2=Saldana-Lopez |first2=A. |last3=Flury |first3=S. |last4=Schaerer |first4=D. |last5=Jaskot |first5=A. |last6=Amorín |first6=R. |last7=Atek |first7=H. |last8=Finkelstein |first8=S. L. |last9=Fleming |first9=B. |last10=Ferguson |first10=H. |last11=Fernández |first11=V. |last12=Giavalisco |first12=M. |last13=Hayes |first13=M. |last14=Heckman |first14=T. |last15=Henry |first15=A. |date=2022-11-09 |title=The far-ultraviolet continuum slope as a Lyman Continuum escape estimator at high redshift |url=https://academic.oup.com/mnras/article/517/4/5104/6753210 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=517 |issue=4 |pages=5104–5120 |doi=10.1093/mnras/stac2874 |doi-access=free |issn=0035-8711|arxiv=2207.05771 }}</ref> 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.<ref>{{Cite journal |last1=Mascia |first1=S. |last2=Pentericci |first2=L. |last3=Calabrò |first3=A. |last4=Treu |first4=T. |last5=Santini |first5=P. |last6=Yang |first6=L. |last7=Napolitano |first7=L. |last8=Roberts-Borsani |first8=G. |last9=Bergamini |first9=P. |last10=Grillo |first10=C. |last11=Rosati |first11=P. |last12=Vulcani |first12=B. |last13=Castellano |first13=M. |last14=Boyett |first14=K. |last15=Fontana |first15=A. |date=April 2023 |title=Closing in on the sources of cosmic reionization: First results from the GLASS-JWST program |url=https://www.aanda.org/10.1051/0004-6361/202345866 |journal=Astronomy & Astrophysics |volume=672 |pages=A155 |doi=10.1051/0004-6361/202345866 |arxiv=2301.02816 |bibcode=2023A&A...672A.155M |s2cid=255546596 |issn=0004-6361}}</ref> Combining these large samples of galaxies with new constraints on the UV luminosity function indicates that dwarf galaxies overwhelmingly contribute to Reionization.<ref>{{Cite journal |last1=Mascia |first1=S. |last2=Pentericci |first2=L. |last3=Calabrò |first3=A. |last4=Santini |first4=P. |last5=Napolitano |first5=L. |last6=Haro |first6=P. Arrabal |last7=Castellano |first7=M. |last8=Dickinson |first8=M. |last9=Ocvirk |first9=P. |last10=Lewis |first10=J. S. W. |last11=Amorín |first11=R. |last12=Bagley |first12=M. |last13=Cleri |first13=R. N. J. |last14=Costantin |first14=L. |last15=Dekel |first15=A. |date=2024 |title=New insight on the nature of cosmic reionizers from the CEERS survey |journal=Astronomy and Astrophysics |volume=685 |pages=A3 |doi=10.1051/0004-6361/202347884 |arxiv=2309.02219|bibcode=2024A&A...685A...3M }}</ref>