Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures
We investigate the relationship between the Ly α forest transmission in the intergalactic medium (IGM) and the environmental density of galaxies, focusing on its implications for the measurement of ionizing radiation escape fractions. Using a sample of 268 spectroscopically confirmed background gala...
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2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adcf9a |
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| author | Claudia M. Scarlata Wanjia Hu Matthew J. Hayes S. Taamoli Ali A. Khostovan C. M. Casey Andreas L. Faisst Jeyhan S. Kartaltepe Yu-Heng Lin Mara Salvato Marc Rafelski |
| author_facet | Claudia M. Scarlata Wanjia Hu Matthew J. Hayes S. Taamoli Ali A. Khostovan C. M. Casey Andreas L. Faisst Jeyhan S. Kartaltepe Yu-Heng Lin Mara Salvato Marc Rafelski |
| author_sort | Claudia M. Scarlata |
| collection | DOAJ |
| description | We investigate the relationship between the Ly α forest transmission in the intergalactic medium (IGM) and the environmental density of galaxies, focusing on its implications for the measurement of ionizing radiation escape fractions. Using a sample of 268 spectroscopically confirmed background galaxies at 2.7 < z < 3.0 and a galaxy density map at z ≈ 2.5 within the COSMOS field, we measure the Ly α transmission photometrically, leveraging the multiwavelength data available from the COSMOS2020 catalog. Our results reveal a weak but statistically significant positive correlation between Ly α optical depth and galaxy density contrast, suggesting that overdense regions are enriched in neutral gas, which could bias escape fraction measurements. This emphasizes the need to account for the large-scale structure of the IGM in analyses of ionizing radiation escape fractions and highlights the advantages of a photometric approach for increasing the number of sampled lines of sight across large fields. The photometric redshifts provided by upcoming all-sky surveys, such as Euclid, will make it possible to account for this bias, which can also be minimized by using fields separated in the sky by many degrees. |
| format | Article |
| id | doaj-art-79ab7b3ca1934fe3aea4e9e0c15bbcec |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-79ab7b3ca1934fe3aea4e9e0c15bbcec2025-08-20T03:07:57ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985111510.3847/1538-4357/adcf9aSystematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale StructuresClaudia M. Scarlata0https://orcid.org/0000-0002-9136-8876Wanjia Hu1Matthew J. Hayes2https://orcid.org/0000-0001-8587-218XS. Taamoli3https://orcid.org/0000-0003-0749-4667Ali A. Khostovan4https://orcid.org/0000-0002-0101-336XC. M. Casey5https://orcid.org/0000-0002-0930-6466Andreas L. Faisst6https://orcid.org/0000-0002-9382-9832Jeyhan S. Kartaltepe7https://orcid.org/0000-0001-9187-3605Yu-Heng Lin8https://orcid.org/0000-0001-8792-3091Mara Salvato9https://orcid.org/0000-0001-7116-9303Marc Rafelski10https://orcid.org/0000-0002-9946-4731Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Street SE, Minneapolis, MN 55455, USAMinnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota , 316 Church Street SE, Minneapolis, MN 55455, USAStockholm University , Department of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691, Stockholm, SwedenPhysics and Astronomy Department, University of California Riverside , USADepartment of Physics and Astronomy, University of Kentucky , 505 Rose Street, Lexington, KY 40506, USADepartment of Physics, University of California , Santa Barbara, CA 93106, USA; Department of Astronomy, the University of Texas at Austin , 2515 Speedway Blvd Stop C1400, Austin, TX 78712, USA; Cosmic DAWN Center , DenmarkCaltech/IPAC , 1200 E. California Blvd. Pasadena, CA 91125, USALaboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology , 84 Lomb Memorial Drive, Rochester, NY 14623, USACaltech/IPAC , 1200 E. California Blvd. Pasadena, CA 91125, USAMax-Planck Institute for Extraterrestrial Physics , Giessenbachstrasse1, 85748, Garching, GermanySpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; Department of Physics and Astronomy, Johns Hopkins University , Baltimore, MD 21218, USAWe investigate the relationship between the Ly α forest transmission in the intergalactic medium (IGM) and the environmental density of galaxies, focusing on its implications for the measurement of ionizing radiation escape fractions. Using a sample of 268 spectroscopically confirmed background galaxies at 2.7 < z < 3.0 and a galaxy density map at z ≈ 2.5 within the COSMOS field, we measure the Ly α transmission photometrically, leveraging the multiwavelength data available from the COSMOS2020 catalog. Our results reveal a weak but statistically significant positive correlation between Ly α optical depth and galaxy density contrast, suggesting that overdense regions are enriched in neutral gas, which could bias escape fraction measurements. This emphasizes the need to account for the large-scale structure of the IGM in analyses of ionizing radiation escape fractions and highlights the advantages of a photometric approach for increasing the number of sampled lines of sight across large fields. The photometric redshifts provided by upcoming all-sky surveys, such as Euclid, will make it possible to account for this bias, which can also be minimized by using fields separated in the sky by many degrees.https://doi.org/10.3847/1538-4357/adcf9aIntergalactic medium |
| spellingShingle | Claudia M. Scarlata Wanjia Hu Matthew J. Hayes S. Taamoli Ali A. Khostovan C. M. Casey Andreas L. Faisst Jeyhan S. Kartaltepe Yu-Heng Lin Mara Salvato Marc Rafelski Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures The Astrophysical Journal Intergalactic medium |
| title | Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures |
| title_full | Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures |
| title_fullStr | Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures |
| title_full_unstemmed | Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures |
| title_short | Systematic Bias in Ionizing Radiation Escape Fraction Measurements from Foreground Large-scale Structures |
| title_sort | systematic bias in ionizing radiation escape fraction measurements from foreground large scale structures |
| topic | Intergalactic medium |
| url | https://doi.org/10.3847/1538-4357/adcf9a |
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