Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light
We present measurements of z ∼ 2.4 ultraviolet (UV) background light using Ly α absorption from galaxies at z ∼ 2–3 in the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) database. Thanks to the wide area of this survey, we also measure the variability of this light across the sky. The data...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adc0f9 |
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| author | Laurel H. Weiss Karl Gebhardt Dustin Davis Erin Mentuch Cooper Maja Lujan Niemeyer Mahdi Qezlou Mahan Mirza Khanlari Robin Ciardullo Daniel Farrow Eric Gawiser Simon Gazagnes Caryl Gronwall Gary J. Hill Donald P. Schneider |
| author_facet | Laurel H. Weiss Karl Gebhardt Dustin Davis Erin Mentuch Cooper Maja Lujan Niemeyer Mahdi Qezlou Mahan Mirza Khanlari Robin Ciardullo Daniel Farrow Eric Gawiser Simon Gazagnes Caryl Gronwall Gary J. Hill Donald P. Schneider |
| author_sort | Laurel H. Weiss |
| collection | DOAJ |
| description | We present measurements of z ∼ 2.4 ultraviolet (UV) background light using Ly α absorption from galaxies at z ∼ 2–3 in the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) database. Thanks to the wide area of this survey, we also measure the variability of this light across the sky. The data suggest an asymmetric geometry where integrated UV light from background galaxies is absorbed by H i within the halo of a foreground galaxy, in a configuration similar to damped Ly α systems. Using stacking analyses of over 400,000 HETDEX LAE spectra, we argue that this background absorption is detectable in our data. We also argue that the absorption signal becomes negative due to HETDEX’s sky-subtraction procedure. The amount that the absorption is oversubtracted is representative of the z ∼ 2.4 UV contribution to the overall extragalactic background light (EBL) at Ly α . Using this method, we determine an average intensity (in νJ _ν units) of 12.9 ± 3.7 nW m ^−2 sr ^−1 at a median observed wavelength of 4134 Å, or a rest-frame UV background intensity of 508 ± 145 nW m ^−2 sr ^−1 at z ∼ 2.4. We find that this flux varies significantly depending on the density of galaxies in the field of observation. Our estimates are consistent with direct measurements of the overall EBL. |
| format | Article |
| id | doaj-art-79f21ae4dbcc474f998b07eec10c0913 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-79f21ae4dbcc474f998b07eec10c09132025-08-20T03:17:13ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198317210.3847/1538-4357/adc0f9Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background LightLaurel H. Weiss0https://orcid.org/0000-0002-4974-1243Karl Gebhardt1https://orcid.org/0000-0002-8433-8185Dustin Davis2https://orcid.org/0000-0002-8925-9769Erin Mentuch Cooper3https://orcid.org/0000-0002-2307-0146Maja Lujan Niemeyer4https://orcid.org/0000-0002-6907-8370Mahdi Qezlou5https://orcid.org/0000-0001-7066-1240Mahan Mirza Khanlari6https://orcid.org/0009-0003-1893-9526Robin Ciardullo7https://orcid.org/0000-0002-1328-0211Daniel Farrow8https://orcid.org/0000-0003-2575-0652Eric Gawiser9https://orcid.org/0000-0003-1530-8713Simon Gazagnes10https://orcid.org/0000-0002-5659-4974Caryl Gronwall11https://orcid.org/0000-0001-6842-2371Gary J. Hill12https://orcid.org/0000-0001-6717-7685Donald P. Schneider13https://orcid.org/0000-0001-7240-7449Department of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USAMax-Planck-Institut für Astrophysik , Karl-Schwarzschild-Str. 1, 85741 Garching, GermanyDepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802, USACentre of Excellence for Data Science, Artificial Intelligence & Modeling (DAIM), University of Hull , Cottingham Road, Hull, HU6 7RX, UK; E. A. Milne Centre for Astrophysics University of Hull , Cottingham Road, Hull, HU6 7RX, UKDepartment of Physics and Astronomy, Rutgers, the State University of New Jersey , Piscataway, NJ 08854, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USADepartment of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USA; McDonald Observatory, The University of Texas at Austin , 2515 Speedway Boulevard, Stop C1402, Austin, TX 78712, USADepartment of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802, USAWe present measurements of z ∼ 2.4 ultraviolet (UV) background light using Ly α absorption from galaxies at z ∼ 2–3 in the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) database. Thanks to the wide area of this survey, we also measure the variability of this light across the sky. The data suggest an asymmetric geometry where integrated UV light from background galaxies is absorbed by H i within the halo of a foreground galaxy, in a configuration similar to damped Ly α systems. Using stacking analyses of over 400,000 HETDEX LAE spectra, we argue that this background absorption is detectable in our data. We also argue that the absorption signal becomes negative due to HETDEX’s sky-subtraction procedure. The amount that the absorption is oversubtracted is representative of the z ∼ 2.4 UV contribution to the overall extragalactic background light (EBL) at Ly α . Using this method, we determine an average intensity (in νJ _ν units) of 12.9 ± 3.7 nW m ^−2 sr ^−1 at a median observed wavelength of 4134 Å, or a rest-frame UV background intensity of 508 ± 145 nW m ^−2 sr ^−1 at z ∼ 2.4. We find that this flux varies significantly depending on the density of galaxies in the field of observation. Our estimates are consistent with direct measurements of the overall EBL.https://doi.org/10.3847/1538-4357/adc0f9GalaxiesDamped Lyα systemsLyα galaxiesDiffuse radiation |
| spellingShingle | Laurel H. Weiss Karl Gebhardt Dustin Davis Erin Mentuch Cooper Maja Lujan Niemeyer Mahdi Qezlou Mahan Mirza Khanlari Robin Ciardullo Daniel Farrow Eric Gawiser Simon Gazagnes Caryl Gronwall Gary J. Hill Donald P. Schneider Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light The Astrophysical Journal Galaxies Damped Lyα systems Lyα galaxies Diffuse radiation |
| title | Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light |
| title_full | Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light |
| title_fullStr | Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light |
| title_full_unstemmed | Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light |
| title_short | Using Lyα Absorption to Measure the Intensity and Variability of z ∼ 2.4 Ultraviolet Background Light |
| title_sort | using lyα absorption to measure the intensity and variability of z ∼ 2 4 ultraviolet background light |
| topic | Galaxies Damped Lyα systems Lyα galaxies Diffuse radiation |
| url | https://doi.org/10.3847/1538-4357/adc0f9 |
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