On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies
We develop a new method to determine the distance between a high-redshift galaxy and a foreground screen of atomic hydrogen. In a partially neutral universe, and assuming spherical symmetry, this equates to the radius of an ionized “bubble” ( R _B ) surrounding the galaxy. The method requires an obs...
| 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 Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/acee6a |
| _version_ | 1797697914010599424 |
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| author | Matthew J. Hayes Claudia Scarlata |
| author_facet | Matthew J. Hayes Claudia Scarlata |
| author_sort | Matthew J. Hayes |
| collection | DOAJ |
| description | We develop a new method to determine the distance between a high-redshift galaxy and a foreground screen of atomic hydrogen. In a partially neutral universe, and assuming spherical symmetry, this equates to the radius of an ionized “bubble” ( R _B ) surrounding the galaxy. The method requires an observed Ly α equivalent width, its velocity offset from systemic, and an input Ly α profile for which we adopt scaled versions of the profiles observed in low- z galaxies. We demonstrate the technique in a sample of 23 galaxies at z > 6, including 8 at z = 7.2–10.6 recently observed with JWST. Our model estimates the emergent Ly α properties and the foreground distance to the absorbing intergalactic medium. We find that galaxies at z > 7.5 occupy smaller bubbles (∼0.5–1 pMpc) than those at lower z . With a relationship that is secure at 99% confidence, we empirically demonstrate the growth of ionized regions during the reionization epoch for the first time. We independently estimate the upper limit on the Strömgren radii ( R _S ), and derive the escape fraction of ionizing photons ( ${f}_{\mathrm{esc}}^{\mathrm{LyC}}$ ) from the ratio of R _B / R _S , deriving a median value of 5%, which, on average, represents the lower end of the photon budget necessary for reionization. |
| first_indexed | 2024-03-12T03:46:45Z |
| format | Article |
| id | doaj.art-ac9f45014bcf4e4e886a1c7d948a8c5e |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-12T03:46:45Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-ac9f45014bcf4e4e886a1c7d948a8c5e2023-09-03T12:49:30ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019541L1410.3847/2041-8213/acee6aOn the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from GalaxiesMatthew J. Hayes0https://orcid.org/0000-0001-8587-218XClaudia Scarlata1https://orcid.org/0000-0002-9136-8876Stockholm University , Department of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691, Stockholm, Sweden ; matthew@astro.su.seMinnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Str. SE, Minneapolis, MN 55455, USAWe develop a new method to determine the distance between a high-redshift galaxy and a foreground screen of atomic hydrogen. In a partially neutral universe, and assuming spherical symmetry, this equates to the radius of an ionized “bubble” ( R _B ) surrounding the galaxy. The method requires an observed Ly α equivalent width, its velocity offset from systemic, and an input Ly α profile for which we adopt scaled versions of the profiles observed in low- z galaxies. We demonstrate the technique in a sample of 23 galaxies at z > 6, including 8 at z = 7.2–10.6 recently observed with JWST. Our model estimates the emergent Ly α properties and the foreground distance to the absorbing intergalactic medium. We find that galaxies at z > 7.5 occupy smaller bubbles (∼0.5–1 pMpc) than those at lower z . With a relationship that is secure at 99% confidence, we empirically demonstrate the growth of ionized regions during the reionization epoch for the first time. We independently estimate the upper limit on the Strömgren radii ( R _S ), and derive the escape fraction of ionizing photons ( ${f}_{\mathrm{esc}}^{\mathrm{LyC}}$ ) from the ratio of R _B / R _S , deriving a median value of 5%, which, on average, represents the lower end of the photon budget necessary for reionization.https://doi.org/10.3847/2041-8213/acee6aReionizationGalaxy evolutionHigh-redshift galaxiesIntergalactic mediumEmission line galaxies |
| spellingShingle | Matthew J. Hayes Claudia Scarlata On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies The Astrophysical Journal Letters Reionization Galaxy evolution High-redshift galaxies Intergalactic medium Emission line galaxies |
| title | On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies |
| title_full | On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies |
| title_fullStr | On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies |
| title_full_unstemmed | On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies |
| title_short | On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies |
| title_sort | on the sizes of ionized bubbles around galaxies during the reionization epoch the spectral shapes of the lyα emission from galaxies |
| topic | Reionization Galaxy evolution High-redshift galaxies Intergalactic medium Emission line galaxies |
| url | https://doi.org/10.3847/2041-8213/acee6a |
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