Lyα Nebulae in HETDEX: The Largest Statistical Census Bridging Lyα Halos and Blobs across Cosmic Noon
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2026
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| author | Cooper, Erin Mentuch Gebhardt, Karl Davis, Dustin Ciardullo, Robin Byrohl, Chris Liu, Chenxu Debski, Maya H. Ortiz, Óscar A. Chávez Fabricius, Maximilian Farrow, Daniel J. Finkelstein, Steven L. Gronwall, Caryl Hill, Gary J. Niemeyer, Maja Lujan McKay, Brianna Mukae, Shiro Ouchi, Masami Röttgering, Huub Schneider, Donald P. Tuttle, Sarah Wisotzki, Lutz Zeimann, Gregory Zhai, Sai |
| author_facet | Cooper, Erin Mentuch Gebhardt, Karl Davis, Dustin Ciardullo, Robin Byrohl, Chris Liu, Chenxu Debski, Maya H. Ortiz, Óscar A. Chávez Fabricius, Maximilian Farrow, Daniel J. Finkelstein, Steven L. Gronwall, Caryl Hill, Gary J. Niemeyer, Maja Lujan McKay, Brianna Mukae, Shiro Ouchi, Masami Röttgering, Huub Schneider, Donald P. Tuttle, Sarah Wisotzki, Lutz Zeimann, Gregory Zhai, Sai |
| contents | The Hobby-Eberly Dark Energy Experiment (HETDEX) is an untargeted ~540 deg^2 spectroscopic survey of Lyα emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1σ Lyα sensitivities of approximately 2-5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, allowing large samples of extended Lyα nebulae (LAN) to be studied. We selected a sample of 70,691 Lyα-emitting galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Lyα emission as a point-source component with an optional exponential envelope. Half (~47.5%) of the LAE sample (33,612 objects) exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Lyα flux and luminosity. Their isophotal areas range from 10-130 arcsec^2 (median 15 arcsec^2), with integrated Lyα fluxes from 6-2000 x 10^-17 erg s^-1 cm^-2 (median 20 x 10^-17 erg s^-1 cm^-2). Comparison between point-spread-function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates the total Lyα flux by ~30% on average, reflecting the substantial halo contribution in extended sources. Approximately 420 LANs are found per deg^2 over 79.5 deg^2 of non-contiguous sky. About 12% of resolved sources show active galactic nuclei signatures and are bright in Lyα and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Lyα flux or luminosity (median 11.6 +/- 1.9 kpc). Only 2.9% of the full S/N > 6 LAE population with ancillary data have radio counterparts, but 64% of those are found to be extended, with the radio fraction increasing with Lyα size. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_06410 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Lyα Nebulae in HETDEX: The Largest Statistical Census Bridging Lyα Halos and Blobs across Cosmic Noon Cooper, Erin Mentuch Gebhardt, Karl Davis, Dustin Ciardullo, Robin Byrohl, Chris Liu, Chenxu Debski, Maya H. Ortiz, Óscar A. Chávez Fabricius, Maximilian Farrow, Daniel J. Finkelstein, Steven L. Gronwall, Caryl Hill, Gary J. Niemeyer, Maja Lujan McKay, Brianna Mukae, Shiro Ouchi, Masami Röttgering, Huub Schneider, Donald P. Tuttle, Sarah Wisotzki, Lutz Zeimann, Gregory Zhai, Sai Astrophysics of Galaxies The Hobby-Eberly Dark Energy Experiment (HETDEX) is an untargeted ~540 deg^2 spectroscopic survey of Lyα emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1σ Lyα sensitivities of approximately 2-5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, allowing large samples of extended Lyα nebulae (LAN) to be studied. We selected a sample of 70,691 Lyα-emitting galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Lyα emission as a point-source component with an optional exponential envelope. Half (~47.5%) of the LAE sample (33,612 objects) exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Lyα flux and luminosity. Their isophotal areas range from 10-130 arcsec^2 (median 15 arcsec^2), with integrated Lyα fluxes from 6-2000 x 10^-17 erg s^-1 cm^-2 (median 20 x 10^-17 erg s^-1 cm^-2). Comparison between point-spread-function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates the total Lyα flux by ~30% on average, reflecting the substantial halo contribution in extended sources. Approximately 420 LANs are found per deg^2 over 79.5 deg^2 of non-contiguous sky. About 12% of resolved sources show active galactic nuclei signatures and are bright in Lyα and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Lyα flux or luminosity (median 11.6 +/- 1.9 kpc). Only 2.9% of the full S/N > 6 LAE population with ancillary data have radio counterparts, but 64% of those are found to be extended, with the radio fraction increasing with Lyα size. |
| title | Lyα Nebulae in HETDEX: The Largest Statistical Census Bridging Lyα Halos and Blobs across Cosmic Noon |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2603.06410 |