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1. Ly α Intensity Mapping in HETDEX: Galaxy-Ly α Intensity Cross-power Spectrum

   https://doi.org/10.3847/1538-4357/ae3a98  

   Lujan_Niemeyer, Maja; Komatsu, Eiichiro; Bernal, José Luis; Byrohl, Chris; Ciardullo, Robin; Curtis, Olivia; Farrow, Daniel J; Finkelstein, Steven L; Gebhardt, Karl; Gronwall, Caryl; et al (March 2026, The Astrophysical Journal)

   Abstract We present a measurement of the Lyαintensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Lyαintensity and Lyα-emitting galaxies (LAEs) in a redshift range of 1.9 ≤z≤ 3.5. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of 5.5. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Lyαintensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, $b_{\mathrm{g}}{b}_I〈I〉{\overline{F}}_{\mathrm{RSD}}/{\overline{F}}_{\mathrm{RSD}}^{\mathrm{fid}}=$ (6.7 ± 3.1), (11.7 ± 1.4), and (8.3 ± 1.5) × 10⁻²²erg s⁻¹cm⁻²arcsec⁻²Å⁻¹in three redshift bins centered at $\overline{z}=2.1$ , 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Lyαradiative transfer. They are, however, significantly smaller than previous results from cross-correlations of quasars with Lyαintensity. These results demonstrate the statistical power of HETDEX for Lyαintensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Lyαemission from galaxies used in modern cosmological simulations of galaxy formation and evolution. 

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2. Radio-detected Ly α emitters at 1.88 < z < 3.52: AGN fraction and Ly α emission

   https://doi.org/10.1051/0004-6361/202558493  

   Zhai, Sai; Röttgering, Huub; Gloudemans, Anniek J; Mentuch_Cooper, Erin; Debski, Maya H; Zeimann, Gregory; Jarvis, Matt J; Morabito, Leah K; Schneider, Donald P; Farrow, Daniel J; et al (September 2026, Astronomy & Astrophysics)

   Context: Ly-alpha emitters (LAEs) are galaxies with strong Ly-alpha emission, tracing early star formation and ionizing radiation. Their connection to active galactic nuclei (AGNs) is key to understanding the mechanisms behind (extended) Ly-alpha emission. Aims: For this study, we measured the fraction of LAEs identified as radio-emitting AGNs and the fraction of radio sources that exhibit Ly-alpha mission to investigate the connection of radio AGN activity to Ly-alpha emission at 1.88 < z < 3.52. Methods: We identified 928 sources that were detected in both the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the LOw Frequency ARray (LOFAR) surveys. These matches were drawn from 55 109 spectroscopically confirmed LAEs and 27 625 radio sources.Results:. After applying completeness corrections, we obtain fAGN,radio = 1.77 ± 0.04% and fLyα = 18.15 ± 0.14% (for Lyα fluxes above 3×10-17 erg s-1 cm-2 and radio flux densities above 0.1 mJy at 144 MHz). The fraction fAGN,radio increases from 0.4 ± 0.1% at log10LLyα,ergs-1 ≈ 42.6 to 9.7 ± 1.3% at log10LLyα,ergs-1 ≈ 44.5. The fraction fLyα rises from 0.7 ± 0.1% at log10L150,WHz-1 ≈ 24.6 to 55.8 ± 14.5% for log10L150,WHz-1 ≈ 28.3. ‘LAEs with radio AGNs’ and ‘optical AGNs with Ly-alpha emission’ exhibit similar radio luminosity distributions above the AGN threshold, though optical AGNs show systematically higher Ly-alpha luminosities. We find no statistically significant correlations of Lyαluminosity with both radio luminosity and a low-frequency spectral index, suggesting that Ly-alpha emission is regulated by gas properties rather than jet power alone. We also find a positive correlation between the full width at half maximum (FWHM) and luminosity of the Ly-alpha line, suggesting that more luminous sources have broader lines, potentially due to enhanced outflows or velocity dispersions. However, we find no correlation between FWHM and radio size, indicating minimal direct jet-gas interaction in these systems. Conclusions: Our results show that most Lyαemission at 1.88 

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3. The Ultraluminous Ly α Luminosity Function at z = 6.6

   https://doi.org/10.3847/1538-4357/ab8ada  

   Taylor, A. J.; Barger, A. J.; Cowie, L. L.; Hu, E. M.; Songaila, A. (June 2020, The Astrophysical Journal)
4. Anomaly in the Opacity of the Post-reionization Intergalactic Medium in the Ly α and Ly β Forest

   https://doi.org/10.3847/1538-4357/ab2b3f  

   Eilers, Anna-Christina; Hennawi, Joseph F.; Davies, Frederick B.; Oñorbe, Jose (August 2019, The Astrophysical Journal)
5. What Makes Ly α Nebulae Glow? Mapping the Polarization of LABd05

   https://doi.org/10.3847/1538-4357/ab837f  

   Kim, Eunchong; Yang, Yujin; Zabludoff, Ann; Smith, Paul; Jannuzi, Buell; Lee, Myung Gyoon; Hwang, Narae; Park, Byeong-Gon (May 2020, The Astrophysical Journal)

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