Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3
The escape fraction of Lyman continuum (LyC) ionizing radiation ( ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ ) is crucial for understanding reionization, yet difficult to measure at z ≳ 4. Recently, studies have focused on calibrating indirect indicators of ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ at z ∼ 0.3, finding...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/add5e6 |
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| author | Annalisa Citro Claudia M. Scarlata Kameswara B. Mantha Liliya R. Williams Marc Rafelski Mitchell Revalski Matthew J. Hayes Alaina Henry Michael J. Rutkowski Harry I. Teplitz Andrea Grazian Anahita Alavi |
| author_facet | Annalisa Citro Claudia M. Scarlata Kameswara B. Mantha Liliya R. Williams Marc Rafelski Mitchell Revalski Matthew J. Hayes Alaina Henry Michael J. Rutkowski Harry I. Teplitz Andrea Grazian Anahita Alavi |
| author_sort | Annalisa Citro |
| collection | DOAJ |
| description | The escape fraction of Lyman continuum (LyC) ionizing radiation ( ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ ) is crucial for understanding reionization, yet difficult to measure at z ≳ 4. Recently, studies have focused on calibrating indirect indicators of ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ at z ∼ 0.3, finding that Ly α is closely linked to it. What is still unclear is whether the LyC–Ly α relation evolves with redshift, and if Ly α is truly applicable as an ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ indicator during the Epoch of Reionization. In this study, we investigate seven −21 ≲ M _UV ≲ −19 gravitationally lensed galaxies from the BOSS Emission-Line Lens Survey for GALaxy-Lyα EmitteR sYstems (or BELLS GALLERY) at z ∼ 2.3. Our targets have rest-frame Ly α equivalent widths between 40 Å and 200 Å and low dust content (−2.4 ≲ β ≲ −2.0), both indicative of high LyC escape. Surprisingly, direct estimates of ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ using Hubble Space Telescope imaging with F275W and F225W reveal that our targets are not LyC emitters, with an absolute ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ < 13% (assuming the median intergalactic medium transmission). The low ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ , coupled with the high Ly α equivalent width and escape fraction, could potentially be attributed to the redshift evolution of the neutral hydrogen column density and dust content, as well as covering fractions of optically thick gas below 1 in high-redshift galaxies. Additionally, our analysis suggests that the emission for each lensed component is uniformly absorbed. Our results challenge the validity of the extrapolation of z ∼ 0 Ly α -based LyC indirect estimators into the Epoch of Reionization. |
| format | Article |
| id | doaj-art-16b5f39c58b440779381bbcb4be02eda |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-16b5f39c58b440779381bbcb4be02eda2025-08-20T02:07:34ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01986218410.3847/1538-4357/add5e6Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3Annalisa Citro0https://orcid.org/0009-0000-9676-0538Claudia M. Scarlata1https://orcid.org/0000-0002-9136-8876Kameswara B. Mantha2https://orcid.org/0000-0002-6016-300XLiliya R. Williams3https://orcid.org/0000-0002-6039-8706Marc Rafelski4https://orcid.org/0000-0002-9946-4731Mitchell Revalski5https://orcid.org/0000-0002-4917-7873Matthew J. Hayes6https://orcid.org/0000-0001-8587-218XAlaina Henry7https://orcid.org/0000-0002-6586-4446Michael J. Rutkowski8https://orcid.org/0000-0001-7016-5220Harry I. Teplitz9https://orcid.org/0000-0002-7064-5424Andrea Grazian10https://orcid.org/0000-0002-5688-0663Anahita Alavi11https://orcid.org/0000-0002-8630-6435Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Street SE, Minneapolis, MN 55455, USA ; acitro@umn.eduMinnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Street SE, Minneapolis, MN 55455, USA ; acitro@umn.eduMissouri Institute for Defense and Energy (MIDE) , 5110 Rockhill Road, University of Missouri Kansas City, MO 64110, USAMinnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Street SE, Minneapolis, MN 55455, USA ; acitro@umn.eduSpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; Department of Physics and Astronomy, Johns Hopkins University , Baltimore, MD 21218, USASpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USADepartment of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, Stockholm University , SE-10691, Stockholm, SwedenSpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USAMinnesota State University-Mankato , Telescope Science Institute, TN141, Mankato, MN 56001, USAIPAC, California Institute of Technology , 1200 E. California Blvd., Pasadena, CA 91125, USAINAF–Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122, Padova, ItalyIPAC, California Institute of Technology , 1200 E. California Blvd., Pasadena, CA 91125, USAThe escape fraction of Lyman continuum (LyC) ionizing radiation ( ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ ) is crucial for understanding reionization, yet difficult to measure at z ≳ 4. Recently, studies have focused on calibrating indirect indicators of ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ at z ∼ 0.3, finding that Ly α is closely linked to it. What is still unclear is whether the LyC–Ly α relation evolves with redshift, and if Ly α is truly applicable as an ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ indicator during the Epoch of Reionization. In this study, we investigate seven −21 ≲ M _UV ≲ −19 gravitationally lensed galaxies from the BOSS Emission-Line Lens Survey for GALaxy-Lyα EmitteR sYstems (or BELLS GALLERY) at z ∼ 2.3. Our targets have rest-frame Ly α equivalent widths between 40 Å and 200 Å and low dust content (−2.4 ≲ β ≲ −2.0), both indicative of high LyC escape. Surprisingly, direct estimates of ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ using Hubble Space Telescope imaging with F275W and F225W reveal that our targets are not LyC emitters, with an absolute ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ < 13% (assuming the median intergalactic medium transmission). The low ${f}_{{\rm{esc}}}^{{\rm{LyC}}}$ , coupled with the high Ly α equivalent width and escape fraction, could potentially be attributed to the redshift evolution of the neutral hydrogen column density and dust content, as well as covering fractions of optically thick gas below 1 in high-redshift galaxies. Additionally, our analysis suggests that the emission for each lensed component is uniformly absorbed. Our results challenge the validity of the extrapolation of z ∼ 0 Ly α -based LyC indirect estimators into the Epoch of Reionization.https://doi.org/10.3847/1538-4357/add5e6ReionizationHigh-redshift galaxiesLyα galaxiesStrong gravitational lensingHST photometry |
| spellingShingle | Annalisa Citro Claudia M. Scarlata Kameswara B. Mantha Liliya R. Williams Marc Rafelski Mitchell Revalski Matthew J. Hayes Alaina Henry Michael J. Rutkowski Harry I. Teplitz Andrea Grazian Anahita Alavi Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 The Astrophysical Journal Reionization High-redshift galaxies Lyα galaxies Strong gravitational lensing HST photometry |
| title | Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 |
| title_full | Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 |
| title_fullStr | Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 |
| title_full_unstemmed | Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 |
| title_short | Challenging the LyC–Lyα Relation: Strong Lyα Emitters without LyC Leakage at z ∼ 2.3 |
| title_sort | challenging the lyc lyα relation strong lyα emitters without lyc leakage at z ∼ 2 3 |
| topic | Reionization High-redshift galaxies Lyα galaxies Strong gravitational lensing HST photometry |
| url | https://doi.org/10.3847/1538-4357/add5e6 |
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