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The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is designed to detect and measure the redshifts of more than 1 million Lyαemitting galaxies (LAEs) 1.88 <z< 3.52. In addition to its cosmological measurements, these data enable studies of Lyαspectral profiles and the underlying radiative transfer. Using the roughly half a million LAEs in the HETDEX Data Release 3, we stack various subsets to obtain the typical Lyαprofile for thez∼ 2–3 epoch and to understand their physical properties. We find clear absorption wings around Lyαemission, which extend ∼2000 km s⁻¹both redward and blueward of the central line. Using far-UV spectra of nearby (0.002 <z< 0.182) LAEs in the COS Legacy Archive Spectroscopic Survey treasury and optical/near-IR spectra of 2.8 <z< 6.7 LAEs in the Multi Unit Spectroscopic-Wide survey, we observe absorption profiles in both redshift regimes. Dividing the sample by volume density shows that the troughs increase in higher-density regions. This trend suggests that the depth of the absorption is dependent on the local density of objects near the LAE, a geometry that is similar to damped Lyαsystems. Simple simulations of Lyαradiative transfer can produce similar troughs due to absorption of light from background sources by Higas surrounding the LAEs.

 

Euclid and the Roman Space Telescope (Roman) will soon use grism spectroscopy to detect millions of galaxies via their Hαand [Oiii]λ5007 emission. To better constrain the expected galaxy counts from these instruments, we use a vetted sample of 4239 emission-line galaxies from the 3D Hubble Space Telescope survey to measure the Hαand [Oiii]λ5007 luminosity functions between 1.16 <z< 1.90; this sample is ∼4 times larger than previous studies at this redshift. We find very good agreement with previous measurements for Hα, but for [Oiii], we predict a higher number of intermediate-luminosity galaxies than from previous works. We find that, for both lines, the characteristic luminosity,${\mathit{}}_{*}$, increases monotonically with redshift, and use the Hαluminosity function to calculate the epoch’s cosmic star formation rate density. We find that Hα-visible galaxies account for ∼81% of the epoch’s total star formation rate, and this value changes very little over the 1.16 <z< 1.56 redshift range. Finally, we derive the surface density of galaxies as a function of limiting flux and find that previous predictions for galaxy counts for the Euclid Wide Survey are unchanged, but there may be more [Oiii] galaxies in the Roman High Latitude Survey than previously estimated.

 

A growing avenue for determining the prevalence of life beyond Earth is to search for “technosignatures” from extraterrestrial intelligences/agents. Technosignatures require significant energy to be visible across interstellar space and thus intentional signals might be concentrated in frequency, in time, or in space, to be found in mutually obvious places. Therefore, it could be advantageous to search for technosignatures in parts of parameter space that are mutually derivable to an observer on Earth and a distant transmitter. In this work, we used theL-band (1.1–1.9 GHz) receiver on the Robert C. Byrd Green Bank Telescope to perform the first technosignature search presynchronized with exoplanet transits, covering 12 Kepler systems. We used the Breakthrough Listen turboSETI pipeline to flag narrowband hits (∼3 Hz) using a maximum drift rate of ±614.4 Hz s⁻¹and a signal-to-noise threshold of 5—the pipeline returned ∼3.4 × 10⁵apparently-localized features. Visual inspection by a team of citizen scientists ruled out 99.6% of them. Further analysis found two signals of interest that warrant follow up, but no technosignatures. If the signals of interest are not redetected in future work, it will imply that the 12 targets in the search are not producing transit-aligned signals from 1.1 to 1.9 GHz with transmitter powers >60 times that of the former Arecibo radar. This search debuts a range of innovative technosignature techniques: citizen science vetting of potential signals of interest, a sensitivity-aware search out to extremely high drift rates, a more flexible method of analyzing on-off cadences, and an extremely low signal-to-noise threshold.

 

We describe the ensemble properties of the 1.9 <z< 3.5 Lyman alpha emitters (LAEs) found in the HETDEX survey’s first public data release, HETDEX Public Source Catalog 1. Stacking the low-resolution (R∼ 800) spectra greatly increases the signal-to-noise ratio (S/N), revealing spectral features otherwise hidden by noise, and we show that the stacked spectrum is representative of an average member of the set. The flux-limited, LyαS/N restricted stack of 50,000 HETDEX LAEs shows the ensemble biweightaveragez∼ 2.6 LAE to be a blue (UV continuum slope ∼ −2.4 andE(B – V)< 0.1), moderately bright (M_UV∼ −19.7) star-forming galaxy with strong Lyαemission (logL_Lyα∼ 42.8 andW_λ(Lyα) ∼ 114 Å), and potentially significant leakage of ionizing radiation. The rest-frame UV light is dominated by a young, metal-poor stellar population with an average age of 5–15 Myr and metallicity of 0.2–0.3Z_⊙.

 

Abstract We present the first publicly released catalog of sources obtained from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). HETDEX is an integral field spectroscopic survey designed to measure the Hubble expansion parameter and angular diameter distance at 1.88 < z < 3.52 by using the spatial distribution of more than a million Ly α -emitting galaxies over a total target area of 540 deg 2 . The catalog comes from contiguous fiber spectra coverage of 25 deg 2 of sky from 2017 January through 2020 June, where object detection is performed through two complementary detection methods: one designed to search for line emission and the other a search for continuum emission. The HETDEX public release catalog is dominated by emission-line galaxies and includes 51,863 Ly α -emitting galaxy (LAE) identifications and 123,891 [O ii ]-emitting galaxies at z < 0.5. Also included in the catalog are 37,916 stars, 5274 low-redshift ( z < 0.5) galaxies without emission lines, and 4976 active galactic nuclei. The catalog provides sky coordinates, redshifts, line identifications, classification information, line fluxes, [O ii ] and Ly α line luminosities where applicable, and spectra for all identified sources processed by the HETDEX detection pipeline. Extensive testing demonstrates that HETDEX redshifts agree to within Δ z < 0.02, 96.1% of the time to those in external spectroscopic catalogs. We measure the photometric counterpart fraction in deep ancillary Hyper Suprime-Cam imaging and find that only 55.5% of the LAE sample has an r -band continuum counterpart down to a limiting magnitude of r ∼ 26.2 mag (AB) indicating that an LAE search of similar sensitivity to HETDEX with photometric preselection would miss nearly half of the HETDEX LAE catalog sample. Data access and details about the catalog can be found online at http://hetdex.org/ . A copy of the catalogs presented in this work (Version 3.2) is available to download at Zenodo doi: 10.5281/zenodo.7448504 . 

We present extended Lyαemission out to 800 kpc of 1034 [Oiii]-selected galaxies at redshifts 1.9 <z< 2.35 using the Hobby–Eberly Telescope Dark Energy Experiment. The locations and redshifts of the galaxies are taken from the 3D-HST survey. The median-stacked surface brightness profile of the Lyαemission of the [Oiii]-selected galaxies agrees well with that of 968 bright Lyα-emitting galaxies (LAEs) atr> 40 kpc from the galaxy centers. The surface brightness in the inner parts (r< 10 kpc) around the [Oiii]-selected galaxies, however, is 10 times fainter than that of the LAEs. Our results are consistent with the notion that photons dominating the outer regions of the Lyαhalos are not produced in the central galaxies but originate outside of them.

 

We present the results of a stellar population analysis of 72 Lyα-emitting galaxies (LAEs) in GOODS-N at 1.9 <z< 3.5 spectroscopically identified by the Hobby−Eberly Telescope Dark Energy Experiment (HETDEX). We provide a method for connecting emission-line detections from the blind spectroscopic survey to imaging counterparts, a crucial tool needed as HETDEX builds a massive database of ∼1 million Lyαdetections. Using photometric data spanning as many as 11 filters covering 0.4 <λ(μm) < 4.5 from the Hubble Space Telescope and Spitzer Space Telescope, we study the objects’ global properties and explore which properties impact the strength of Lyαemission. We measure a median stellar mass of${0.8}_{-0.5}^{+2.9}\times {10}^9{M}_{\odot }$and conclude that the physical properties of HETDEX spectroscopically selected LAEs are comparable to LAEs selected by previous deep narrowband studies. We find that stellar mass and star formation rate correlate strongly with the Lyαequivalent width. We then use a known sample ofz> 7 LAEs to perform a protostudy of predicting Lyαemission from galaxies in the epoch of reionization, finding agreement at the 1σlevel between prediction and observation for the majority of strong emitters.

 

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.

 

We describe the survey design, calibration, commissioning, and emission-line detection algorithms for the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the redshifts of over a million Lyαemitting galaxies between 1.88 <z< 3.52, in a 540 deg²area encompassing a comoving volume of 10.9 Gpc³. No preselection of targets is involved; instead the HETDEX measurements are accomplished via a spectroscopic survey using a suite of wide-field integral field units distributed over the focal plane of the telescope. This survey measures the Hubble expansion parameter and angular diameter distance, with a final expected accuracy of better than 1%. We detail the project’s observational strategy, reduction pipeline, source detection, and catalog generation, and present initial results for science verification in the Cosmological Evolution Survey, Extended Groth Strip, and Great Observatories Origins Deep Survey North fields. We demonstrate that our data reach the required specifications in throughput, astrometric accuracy, flux limit, and object detection, with the end products being a catalog of emission-line sources, their object classifications, and flux-calibrated spectra.