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Abstract The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is a large-volume spectroscopic survey without preselection of sources, searching ∼540 deg 2 for Ly α emitting galaxies (LAEs) at 1.9 < z < 3.5. Taking advantage of such a wide-volume survey, we perform a pilot study using early HETDEX data to search for lensed Ly α emitters (LAEs). After performing a proof of concept using a previously known lensed LAE covered by HETDEX, we perform a search for previously unknown lensed LAEs in the HETDEX spectroscopic sample. We present a catalog of 26 potential LAEs lensed by foreground, red, non-star-forming galaxies at z ∼ 0.4–0.7. We estimate the magnification for each candidate system, finding 12 candidates to be within the strong lensing regime (magnification μ > 2). Follow-up observations of these potential lensed LAEs have the potential to confirm their lensed nature and explore these distant galaxies in more detail.
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This content will become publicly available on April 29, 2027
Enhancing Ly α Emitter Identification in HETDEX with a Convolutional Neural Network
Abstract We present a deep learning framework to enhance the identification of Lyαemitters (LAEs) in the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX), an untargeted spectroscopic survey of LAEs at 1.9 < z < 3.5 without imaging preselection. We primarily address the low signal-to-noise ratio (S/N) regime (4.8 ≤ S/N ≤ 5.5), where LAE candidates suffer from substantial noise contamination. To distinguish LAE candidates from artifacts and sky residuals, we employ a convolutional neural network (CNN) trained on two-dimensional spectral images of single emission lines. The training sample is constructed from the HETDEX COSMOS catalog, with external validation from ancillary observations and our participatory science project, Dark Energy Explorers. For small-format, low-resolution spectroscopic data, the model achieves a balanced accuracy, precision, and recall of 94.1%, 97.5%, and 97.5%, respectively, in the high-S/N regime (S/N > 5.5), and 85.1%, 78.2%, and 84.4% in the low-S/N regime. Using HETDEX LAEs independently identified by Dark Energy Spectroscopic Instrument (DESI) spectroscopy, the model recovers 99% and 93% of the high- and low-S/N LAEs, respectively. Visual attribution indicates that the CNN attends to smooth, spatially extended central emission in true positives and to irregular or noisy features in true negatives. Applied to the full HETDEX catalog, the CNN enables an S/N threshold down to 4.8 by suppressing spurious spikes acrossz ∼ 1.9–2.5 in the redshift distribution. Our approach facilitates HETDEX cosmological analyses by mitigating false positives in galaxy clustering and highlights the value of domain-specific deep learning for refining low-S/N spectroscopic identification in untargeted surveys.
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- PAR ID:
- 10709579
- Publisher / Repository:
- AJ
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 171
- Issue:
- 5
- ISSN:
- 0004-6256
- Page Range / eLocation ID:
- 318
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The Hobby–Eberly Dark Energy Experiment (HETDEX) is an untargeted ∼540 deg^2 spectroscopic survey of Ly-alpha emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1 sigma Ly-alpha sensitivities of ∼2─5 × 10^−18 erg s−1 cm^−2 arcsec^−2 , allowing large samples of extended Ly-alpha nebulae (LAN) to be studied. We selected a sample of 70,691 Ly-alpha emitting galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Ly-alpha 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 Ly-alpha flux and luminosity. Their isophotal areas range from 10 to 130 arcsec^2 (median 15 arcsec^2), with integrated Ly-alpha luxes from 6 to 2000 × 10^−17 erg s^−1 cm^−2 (median 20 × 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 Ly-alpha 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 noncontiguous sky. About 12% of resolved sources show active galactic nuclei signatures and are bright in Ly-alpha and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Ly-alpha 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 Ly-alpha size. We present a catalog of all modeled sources, with their positions, redshifts, luminosities, and structural parameters for over 70,000 LAEs consisting of 33,000 spatially extended LAN.more » « less
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