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1. Surface Brightness Profile of Lyman-α Halos out to 320 kpc in HETDEX

   https://doi.org/10.3847/1538-4357/ac5cb8  

   Lujan Niemeyer, Maja ; Komatsu, Eiichiro ; Byrohl, Chris ; Davis, Dustin ; Fabricius, Maximilian ; Gebhardt, Karl ; Hill, Gary J. ; Wisotzki, Lutz ; Bowman, William P. ; Ciardullo, Robin ; et al ( April 2022 , The Astrophysical Journal)

   We present the median-stacked Lyman-α (Lyα) surface brightness profiles of 968 spectroscopically selected Lyαemitting galaxies (LAEs) at redshifts 1.9 <z< 3.5 in the early data of the Hobby-Eberly Telescope Dark Energy Experiment. The selected LAEs are high-confidence Lyαdetections with high signal-to-noise ratios observed with good seeing conditions (point-spread function FWHM <1.″4), excluding active galactic nuclei. The Lyαluminosities of the LAEs are 10^42.4–10⁴³erg s⁻¹. We detect faint emission in the median-stacked radial profiles at the level of$(3.6\pm 1.3)\times {10}^{-20}\mathrm{erg}{\mathrm{s}}^{-1}{\mathrm{cm}}^{-2}{\mathrm{arcsec}}^{-2}$from the surrounding Lyαhalos out tor≃ 160 kpc (physical). The shape of the median-stacked radial profile is consistent atr< 80 kpc with that of much fainter LAEs at 3 <z< 4 observed with the Multi Unit Spectroscopic Explorer (MUSE), indicating that the median-stacked Lyαprofiles have similar shapes at redshifts 2 <z< 4 and across a factor of 10 in Lyαluminosity. While we agree with the results from the MUSE sample atr< 80 kpc, we extend the profile over a factor of two in radius. Atr> 80 kpc, our profile is flatter than the MUSE model. The measured profile agrees at most radii with that of galaxies in the Byrohl et al. cosmological radiative transfer simulation atz= 3. This suggests that the surface brightness of a Lyαhalo atr≲ 100 kpc is dominated by resonant scattering of Lyαphotons from star-forming regions in the central galaxy, whereas atr> 100 kpc, it is dominated by photons from galaxies in surrounding dark matter halos.

    

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2. ODIN: Improved Narrowband Lyα Emitter Selection Techniques for z = 2.4, 3.1, and 4.5

   https://doi.org/10.3847/1538-4357/ad71c9  

   Firestone, Nicole_M ; Gawiser, Eric ; Ramakrishnan, Vandana ; Lee, Kyoung-Soo ; Valdes, Francisco ; Park, Changbom ; Yang, Yujin ; Ciardullo, Robin ; Artale, María_Celeste ; Benda, Barbara ; et al ( October 2024 , The Astrophysical Journal)

   Lyman-alpha-emitting galaxies (LAEs) are typically young, low-mass, star-forming galaxies with little extinction from interstellar dust. Their low dust attenuation allows their Lyαemission to shine brightly in spectroscopic and photometric observations, providing an observational window into the high-redshift Universe. Narrowband surveys reveal large, uniform samples of LAEs at specific redshifts that probe large-scale structure and the temporal evolution of galaxy properties. The One-hundred-deg²DECam Imaging in Narrowbands (ODIN) utilizes three custom-made narrowband filters on the Dark Energy Camera (DECam) to discover LAEs at three equally spaced periods in cosmological history. In this paper, we introduce the hybrid-weighted double-broadband continuum estimation technique, which yields improved estimation of Lyαequivalent widths. Using this method, we discover 6032, 5691, and 4066 LAE candidates atz= 2.4, 3.1, and 4.5 in the extended COSMOS field (∼9 deg²). We find that [Oii] emitters are a minimal contaminant in our LAE samples, but that interloping Green Pea–like [Oiii] emitters are important for our redshift 4.5 sample. We introduce an innovative method for identifying [Oii] and [Oiii] emitters via a combination of narrowband excess and galaxy colors, enabling their study as separate classes of objects. We present scaled median stacked spectral energy distributions for each galaxy sample, revealing the overall success of our selection methods. We also calculate rest-frame Lyαequivalent widths for our LAE samples and find that the EW distributions are best fit by exponential functions with scale lengths ofw₀= 53 ± 1, 65 ± 1, and 59 ± 1 Å, respectively.

    

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3. A Survey of Lyα Emission around Damped Lyα Absorbers at z ≈ 2 with the Keck Cosmic Web Imager

   https://doi.org/10.3847/1538-4357/ad1182  

   Oyarzún, Grecco A. ; Rafelski, Marc ; Kanekar, Nissim ; Prochaska, J. Xavier ; Neeleman, Marcel ; Jorgenson, Regina A. ( February 2024 , The Astrophysical Journal)

   We present Keck Cosmic Web Imager Lyαintegral field spectroscopy of the fields surrounding 14 damped Lyαabsorbers (DLAs) atz≈ 2. Of these 14 DLAs, nine have high metallicities ([M/H] > − 0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Lyαline flux sensitivities of ∼2 × 10⁻¹⁷erg s⁻¹cm⁻²over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Lyαflux of three known Lyα-emitting Hi-selected galaxies in our sample. In addition, we find two Lyαemitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA atz≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Lyαemission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Lyαemitters, we conclude that Hi-selected galaxies associated with high-metallicity DLAs atz≈ 2 are dusty and therefore might feature low Lyαescape fractions. Our results indicate that complementary approaches—using Lyα, CO, Hα, and [Cii] 158μm emission—are necessary to identify the wide range of galaxy types associated withz≈ 2 DLAs.

    

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4. The One-hundred-deg 2 DECam Imaging in Narrowbands (ODIN): Survey Design and Science Goals

   https://doi.org/10.3847/1538-4357/ad165e  

   Lee, Kyoung-Soo ; Gawiser, Eric ; Park, Changbom ; Yang, Yujin ; Valdes, Francisco ; Lang, Dustin ; Ramakrishnan, Vandana ; Moon, Byeongha ; Firestone, Nicole ; Appleby, Stephen ; et al ( February 2024 , The Astrophysical Journal)

   We describe the survey design and science goals for One-hundred-deg²DECam Imaging in Narrowbands (ODIN), a NOIRLab survey using the Dark Energy Camera (DECam) to obtain deep (AB ∼ 25.7) narrowband images over an unprecedented area of sky. The three custom-built narrowband filters,N419,N501, andN673, have central wavelengths of 419, 501, and 673 nm and respective FWHM of 7.5, 7.6, and 10.0 nm, corresponding to Lyαatz= 2.4, 3.1, and 4.5 and cosmic times of 2.8, 2.1, and 1.4 Gyr, respectively. When combined with even deeper, public broadband data from the Hyper Suprime-Cam, DECam, and in the future, the Legacy Survey of Space and Time, the ODIN narrowband images will enable the selection of over 100,000 Lyα-emitting (LAE) galaxies at these epochs. ODIN-selected LAEs will identify protoclusters as galaxy overdensities, and the deep narrowband images enable detection of highly extended Lyαblobs (LABs). Primary science goals include measuring the clustering strength and dark matter halo connection of LAEs, LABs, and protoclusters, and their respective relationship to filaments in the cosmic web. The three epochs allow for the redshift evolution of these properties to be determined during the period known as Cosmic Noon, where star formation was at its peak. The narrowband filter wavelengths are designed to enable interloper rejection and further scientific studies by revealing [Oii] and [Oiii] atz= 0.34, Lyαand Heii1640 atz= 3.1, and Lyman continuum plus Lyαatz= 4.5. Ancillary science includes similar studies of the lower-redshift emission-line galaxy samples and investigations of nearby star-forming galaxies resolved into numerous [Oiii] and [Sii] emitting regions.

    

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5. Lyα Emission Line Profiles of Extreme [O iii]- emitting Galaxies at z ≳ 2: Implications for Lyα Visibility in the Reionization Era

   https://doi.org/10.3847/1538-4357/ad5ae0  

   Tang, Mengtao ; Stark, Daniel_P ; Ellis, Richard_S ; Topping, Michael_W ; Mason, Charlotte ; Li, Zhihui ; Plat, Adèle ( August 2024 , The Astrophysical Journal)

   JWST observations have recently begun delivering the first samples of Lyαvelocity profile measurements atz> 6, opening a new window into the reionization process. Interpretation ofz≳ 6 line profiles is currently stunted by limitations in our knowledge of the intrinsic Lyαprofile (before encountering the intergalactic medium (IGM)) of the galaxies that are common atz≳ 6. To overcome this shortcoming, we have obtained resolved (R∼ 3900) Lyαspectroscopy of 42 galaxies atz= 2.1–3.4 with similar properties as are seen atz> 6. We quantify a variety of Lyαprofile statistics as a function of [Oiii]+Hβequivalent width (EW). Our spectra reveal a new population ofz≃ 2–3 galaxies with large [Oiii]+HβEWs (>1200 Å) and a large fraction of Lyαflux emerging near the systemic redshift (peak velocity ≃0 km s⁻¹). These spectra indicate that low-density neutral hydrogen channels are able to form in a subset of low-mass galaxies (≲1 × 10⁸M_⊙) that experience a burst of star formation (sSFR > 100 Gyr⁻¹). Other extreme [Oiii] emitters show weaker Lyαthat is shifted to higher velocities (≃240 km s⁻¹) with little emission near the line center. We investigate the impact the IGM is likely to have on these intrinsic line profiles in the reionization era, finding that the centrally peaked Lyαemitters should be strongly attenuated atz≳ 5. We show that these line profiles are particularly sensitive to the impact of resonant scattering from infalling IGM and can be strongly attenuated even when the IGM is highly ionized atz≃ 5. We compare these expectations against a new database ofz≳ 6.5 galaxies with robust velocity profiles measured with JWST/NIRSpec.

    

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