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We present a 0.3–4.5μm 16-band photometric catalog for the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers an ∼27 deg²field within the footprint of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). Here we present new DECam imaging and anrizK_sband–selected catalog of four million sources extracted using a fully model-based approach. We validate our photometry by comparing with the model-based DECam Legacy Survey. We analyze the differences between model-based and aperture photometry by comparing with the previous SHELA catalog, finding that our model-based photometry can measure point sources to fainter fluxes and better capture the full emission of resolved sources. The catalog is 80% (50%) complete atriz∼ 24.7 (25.1) AB mag, and the optical photometry reaches a 5σdepth of ∼25.5 AB mag. We measure photometric redshifts and achieve a 1σscatter of Δz/(1 +z) of 0.04 with available spectroscopic redshifts at 0 ≤z≤ 1. This large-area, multiwavelength photometric catalog, combined with spectroscopic information from HETDEX, will enable a wide range of extragalactic science investigations.

 

Abstract We used data from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) to study the incidence of AGN in continuum-selected galaxies at z ∼ 3. From optical and infrared imaging in the 24 deg 2 Spitzer HETDEX Exploratory Large Area survey, we constructed a sample of photometric-redshift selected z ∼ 3 galaxies. We extracted HETDEX spectra at the position of 716 of these sources and used machine-learning methods to identify those which exhibited AGN-like features. The dimensionality of the spectra was reduced using an autoencoder, and the latent space was visualized through t-distributed stochastic neighbor embedding. Gaussian mixture models were employed to cluster the encoded data and a labeled data set was used to label each cluster as either AGN, stars, high-redshift galaxies, or low-redshift galaxies. Our photometric redshift (photo z ) sample was labeled with an estimated 92% overall accuracy, an AGN accuracy of 83%, and an AGN contamination of 5%. The number of identified AGN was used to measure an AGN fraction for different magnitude bins. The ultraviolet (UV) absolute magnitude where the AGN fraction reaches 50% is M UV = −23.8. When combined with results in the literature, our measurements of AGN fraction imply that the bright end of the galaxy luminosity function exhibits a power law rather than exponential decline, with a relatively shallow faint-end slope for the z ∼ 3 AGN luminosity function. 

Abstract The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields (UVCANDELS) program provides Hubble Space Telescope (HST)/UVIS F275W imaging for four CANDELS fields. We combine this UV imaging with existing HST/near-IR grism spectroscopy from 3D-HST+AGHAST to directly compare the resolved rest-frame UV and H α emission for a sample of 979 galaxies at 0.7 < z < 1.5, spanning a range in stellar mass of 10 8−11.5 M ⊙ . Using a stacking analysis, we perform a resolved comparison between homogenized maps of rest-UV and H α to compute the average UV-to-H α luminosity ratio (an indicator of burstiness in star formation) as a function of galactocentric radius. We find that galaxies below stellar mass of ∼10 9.5 M ⊙ , at all radii, have a UV-to-H α ratio higher than the equilibrium value expected from constant star formation, indicating a significant contribution from bursty star formation. Even for galaxies with stellar mass ≳10 9.5 M ⊙ , the UV-to-H α ratio is elevated toward their outskirts ( R / R eff > 1.5), suggesting that bursty star formation is likely prevalent in the outskirts of even the most massive galaxies, but is likely overshadowed by their brighter cores. Furthermore, we present the UV-to-H α ratio as a function of galaxy surface brightness, a proxy for stellar mass surface density, and find that regions below ∼10 7.5 M ⊙ kpc −2 are consistent with bursty star formation, regardless of their galaxy stellar mass, potentially suggesting that local star formation is independent of global galaxy properties at the smallest scales. Last, we find galaxies at z > 1.1 to have bursty star formation, regardless of radius or surface brightness. 

While many Lyαblobs (LABs) are found in and around several well-known protoclusters at high redshift, how they trace the underlying large-scale structure is still poorly understood. In this work, we utilize 5352 Lyαemitters (LAEs) and 129 LABs atz= 3.1 identified over a ∼9.5 deg²area in early data from the ongoing One-hundred-deg²DECam Imaging in Narrowbands (ODIN) survey to investigate this question. Using LAEs as tracers of the underlying matter distribution, we identify overdense structures as galaxy groups, protoclusters, and filaments of the cosmic web. We find that LABs preferentially reside in regions of higher-than-average density and are located in closer proximity to overdense structures, which represent the sites of protoclusters and their substructures. Moreover, protoclusters hosting one or more LABs tend to have a higher descendant mass than those which do not. Blobs are also strongly associated with filaments of the cosmic web, with ∼70% of the population being within a projected distance of ∼2.4 pMpc from a filament. We show that the proximity of LABs to protoclusters is naturally explained by their association with filaments as large cosmic structures are where many filaments converge. The contiguous wide-field coverage of the ODIN survey allows us to establish firmly a connection between LABs as a population and filaments of the cosmic web for the first time.

 

Abstract The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted spectroscopic survey that aims to measure the expansion rate of the universe at z ∼ 2.4 to 1% precision for both H ( z ) and D A ( z ). HETDEX is in the process of mapping in excess of one million Ly α emitting (LAE) galaxies and a similar number of lower- z galaxies as a tracer of the large-scale structure. The success of the measurement is predicated on the post-observation separation of galaxies with Ly α emission from the lower- z interloping galaxies, primarily [O ii ], with low contamination and high recovery rates. The Emission Line eXplorer (ELiXer) is the principal classification tool for HETDEX, providing a tunable balance between contamination and completeness as dictated by science needs. By combining multiple selection criteria, ELiXer improves upon the 20 Å rest-frame equivalent width cut commonly used to distinguish LAEs from lower- z [O ii ] emitting galaxies. Despite a spectral resolving power, R ∼ 800, that cannot resolve the [O ii ] doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Ly α by [O ii ] of 1.2% and a Ly α recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements. 

We investigate the stellar mass–black hole mass (${\mathit{}}_{*}–{\mathit{}}_{\mathrm{BH}}$) relation with type 1 active galactic nuclei (AGNs) down to${\mathit{}}_{\mathrm{BH}}={10}^7{M}_{\odot }$, corresponding to a ≃ −21 absolute magnitude in rest-frame ultraviolet, atz= 2–2.5. Exploiting the deep and large-area spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX), we identify 66 type 1 AGNs with${\mathit{}}_{\mathrm{BH}}$ranging from 10⁷–10¹⁰M_⊙that are measured with single-epoch virial method using Civemission lines detected in the HETDEX spectra.${\mathit{}}_{*}$of the host galaxies are estimated from optical to near-infrared photometric data taken with Spitzer, the Wide-field Infrared Survey Explorer, and ground-based 4–8 m class telescopes byCIGALEspectral energy distribution (SED) fitting. We further assess the validity of SED fitting in two cases by host-nuclear decomposition performed through surface brightness profile fitting on spatially resolved host galaxies with the James Webb Space Telescope/NIRCam CEERS data. We obtain the${\mathit{}}_{*}–{\mathit{}}_{\mathrm{BH}}$relation covering the unexplored low-mass ranges of${\mathit{}}_{\mathrm{BH}}\sim {10}^7–{10}^8{M}_{\odot }$, and conduct forward modeling to fully account for the selection biases and observational uncertainties. The intrinsic${\mathit{}}_{*}–{\mathit{}}_{\mathrm{BH}}$relation atz∼ 2 has a moderate positive offset of 0.52 ± 0.14 dex from the local relation, suggestive of more efficient black hole growth at higher redshift even in the low-mass regime of${\mathit{}}_{\mathrm{BH}}\sim {10}^7–{10}^8{M}_{\odot }$. Our${\mathit{}}_{*}–{\mathit{}}_{\mathrm{BH}}$relation is inconsistent with the${\mathit{}}_{\mathrm{BH}}$suppression at the low-${\mathit{}}_{*}$regime predicted by recent hydrodynamic simulations at a 98% confidence level, suggesting that feedback in the low-mass systems may be weaker than those produced in hydrodynamic simulations.

 

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.

 

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_⊙.

 

We report an active galactic nucleus (AGN) with an extremely high equivalent width (EW), EW_{Lyα+N V,rest}≳921Å, in the rest frame, atz∼ 2.24 in the Hobby–Eberly Telescope Dark Energy Experiment Survey (HETDEX), as a representative case of the high-EW AGN population. The continuum level is a nondetection in the HETDEX spectrum; thus the measured EW is a lower limit. The source is detected with significant emission lines (>7σ) at Lyα+ Nvλ1241, Civλ1549, and a moderate emission line (∼4σ) at Heiiλ1640 within the wavelength coverage of HETDEX (3500–5500 Å). Ther-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit ofr= 25.12 at 5σ. The Lyαemission line spans a clearly resolved region of ∼10″ (85 kpc) in diameter. The Lyαline profile is strongly double peaked. The spectral decomposed blue gas and red gas Lyαemission are separated by ∼1.″2 (10.1 kpc) with a line-of-sight velocity offset of ∼1100 km s⁻¹. This source is probably an obscured AGN with powerful winds.