Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7
Although low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most simulations indicate the former is the best candidate, some models suggest that at z ≥ 6 massive, UV-bright galaxi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acac9d |
| _version_ | 1797701242582990848 |
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| author | Callum E. C. Witten Nicolas Laporte Harley Katz |
| author_facet | Callum E. C. Witten Nicolas Laporte Harley Katz |
| author_sort | Callum E. C. Witten |
| collection | DOAJ |
| description | Although low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most simulations indicate the former is the best candidate, some models suggest that at z ≥ 6 massive, UV-bright galaxies – “oligarchs” – account for at least 80% of the ionizing budget. To test this hypothesis, we target massive ( ${\mathrm{log}}_{10}({\text{}}{M}_{\star }[{\text{}}{M}_{\odot }])\gt 10$ ), UV-bright ( M _UV ∼ −22) Ly α emitters at z > 7 in archival data, observed with similar resolution spectrographs (Very Large Telescope/X-shooter and Keck/MOSFIRE). To increase the reliability of our conclusions, we stack all spectra and obtain a deep-stacked spectrum of 24.75 hr. The stacked Ly α profile displays a clear asymmetric red peak and an absence of a blue peak. We additionally estimate the intrinsic stacked Ly α profile of our targets by correcting for intergalactic medium (IGM) transmission using a range of neutral hydrogen fractions, finding no significant change in the profile. We measure a velocity offset V _red > 300 km s ^−1 and an asymmetry in our red peak A ∼ 3. Using various models and estimators, such as the peak separation, the asymmetry of the red peak, the ratio between Ly α and H β, and the β slope, we conclude that the escape fraction in these three UV-bright, massive (∼10 ^10 M _⊙ ), z ≥ 7 galaxies is f _esc (LyC) ≤ 10%. |
| first_indexed | 2024-03-12T04:33:38Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:33:38Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-3502f831408c472b95140d3524e624df2023-09-03T09:58:17ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194416110.3847/1538-4357/acac9dEvidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7Callum E. C. Witten0https://orcid.org/0000-0002-1369-6452Nicolas Laporte1https://orcid.org/0000-0001-7459-6335Harley Katz2https://orcid.org/0000-0003-1561-3814Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UK ; cw795@cam.ac.ukKavli Institute for Cosmology, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UK; Cavendish Laboratory, University of Cambridge , 19 JJ Thomson Avenue, Cambridge CB3 0HE, UKSub-department of Astrophysics, University of Oxford , Keble Road, Oxford OX1 3RH, UKAlthough low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most simulations indicate the former is the best candidate, some models suggest that at z ≥ 6 massive, UV-bright galaxies – “oligarchs” – account for at least 80% of the ionizing budget. To test this hypothesis, we target massive ( ${\mathrm{log}}_{10}({\text{}}{M}_{\star }[{\text{}}{M}_{\odot }])\gt 10$ ), UV-bright ( M _UV ∼ −22) Ly α emitters at z > 7 in archival data, observed with similar resolution spectrographs (Very Large Telescope/X-shooter and Keck/MOSFIRE). To increase the reliability of our conclusions, we stack all spectra and obtain a deep-stacked spectrum of 24.75 hr. The stacked Ly α profile displays a clear asymmetric red peak and an absence of a blue peak. We additionally estimate the intrinsic stacked Ly α profile of our targets by correcting for intergalactic medium (IGM) transmission using a range of neutral hydrogen fractions, finding no significant change in the profile. We measure a velocity offset V _red > 300 km s ^−1 and an asymmetry in our red peak A ∼ 3. Using various models and estimators, such as the peak separation, the asymmetry of the red peak, the ratio between Ly α and H β, and the β slope, we conclude that the escape fraction in these three UV-bright, massive (∼10 ^10 M _⊙ ), z ≥ 7 galaxies is f _esc (LyC) ≤ 10%.https://doi.org/10.3847/1538-4357/acac9dLyman-alpha galaxiesReionizationHigh-redshift galaxies |
| spellingShingle | Callum E. C. Witten Nicolas Laporte Harley Katz Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 The Astrophysical Journal Lyman-alpha galaxies Reionization High-redshift galaxies |
| title | Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 |
| title_full | Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 |
| title_fullStr | Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 |
| title_full_unstemmed | Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 |
| title_short | Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7 |
| title_sort | evidence for a low lyman continuum escape fraction in three massive ultraviolet bright galaxies at z 7 |
| topic | Lyman-alpha galaxies Reionization High-redshift galaxies |
| url | https://doi.org/10.3847/1538-4357/acac9d |
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