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1. Euclid preparation: LXI. Cosmic Dawn Survey: ‘Pre-launch’ multiwavelength catalogues for EuclidDeep Field North and Euclid Deep Field Fornax

   https://doi.org/10.1051/0004-6361/202451857  

   Zalesky, L; McPartland, C_J R; Weaver, J R; Toft, S; Sanders, D B; Mobasher, B; Suzuki, N; Szapudi, I; Valdes, I; Murphree, G; et al (March 2025, Astronomy & Astrophysics)

   The Cosmic Dawn Survey (DAWN survey) provides multiwavelength (UV/optical to mid-IR) data across the combined 59 deg²of the Euclid Deep and Auxiliary fields (EDFs and EAFs). In this work, the first public data release from the DAWN survey is presented. The catalogues made available herein consist of a subset of the full DAWN survey that includes two EDFs: EDF North (EDF-N) and EDF Fornax (EDF-F). Each field has been covered by the ongoing Hawaii Twenty Square Degree Survey (H20), which includes imaging from the CFHT MegaCam in theufilter and from the Subaru Hyper Suprime-Cam (HSC) in thegrizfilters. Each field has been further covered bySpitzer/IRAC 3.6–4.5µm imaging spanning 10 deg²and reaching ~25 mag AB (5σ). All present H20 imaging and all publicly available imaging from the aforementioned facilities were combined with the deepSpitzer/IRAC data to create source catalogues spanning a total area of 16.87 deg²in EDF-N and 2.85 deg²in EDF-F for this first release. These catalogues are referred to as the ‘pre-launch’ (PL), asEucliddata is not yet public for these fields and therefore it is not included. Photometry was measured from these multiwavelength data usingThe Farmer, a novel and well validated model-based photometry code. Photometric redshifts and stellar masses were computed using two independent codes for modelling spectral energy distributions:EAZYandLePhare. Photometric redshifts show good agreement with spectroscopic redshifts (σ_NMAD~ 0.5,η <8% ati< 25). Number counts, photometric redshifts and stellar masses were further validated in comparison to the COSMOS2020 catalogue. The DAWN survey PL catalogues are designed to be of immediate use in these two EDFs and will be continuously updated and made available as both new ground-based data and spaced-based data fromEuclidare acquired and made public. Future data releases will provide catalogues of all EDFs and EAFs and includeEucliddata. 

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2. PEARLS: Near-infrared Photometry in the JWST North Ecliptic Pole Time Domain Field*

   https://doi.org/10.3847/1538-4365/acf57d  

   Willmer, Christopher_N A; Ly, Chun; Kikuta, Satoshi; Kattner, S A; Jansen, Rolf A; Cohen, Seth H; Windhorst, Rogier A; Smail, Ian; Tompkins, Scott; Beacom, John F; et al (November 2023, The Astrophysical Journal Supplement Series)

   Abstract We present near-infrared (NIR) ground-basedY,J,H, andKimaging obtained in the James Webb Space Telescope (JWST) North Ecliptic Pole Time Domain Field (NEP TDF) using the MMT-Magellan Infrared Imager and Spectrometer on the MMT. These new observations cover a field of approximately 230 arcmin²inY,H, andK,and 313 arcmin²inJ. Using Monte Carlo simulations, we estimate a 1σdepth relative to the background sky of (Y, J, H, K) = (23.80, 23.53, 23.13, 23.28) in AB magnitudes for point sources at a 95% completeness level. These observations are part of the ground-based effort to characterize this region of the sky, supplementing space-based data obtained with Chandra, NuSTAR, XMM, AstroSat, Hubble Space Telescope, and JWST. This paper describes the observations and reduction of the NIR imaging and combines these NIR data with archival imaging in the visible, obtained with the Subaru Hyper-Suprime-Cam, to produce a merged catalog of 57,501 sources. The new observations reported here, plus the corresponding multiwavelength catalog, will provide a baseline for time-domain studies of bright sources in the NEP TDF. 

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3. Subaru/Hyper Suprime-Cam z-Broadband Excess Selection of Extreme Emission Line Galaxies at z < 1

   https://doi.org/10.3847/1538-4357/ac5117  

   Rosenwasser, Benjamin E.; Taylor, Anthony J.; Barger, Amy J.; Cowie, Lennox L.; Hu, Esther M.; Jones, Logan H.; Songaila, Antoinette (March 2022, The Astrophysical Journal)

   Abstract We present a search for extreme emission line galaxies (EELGs) at z < 1 in the COSMOS and North Ecliptic Pole (NEP) fields with imaging from Subaru/Hyper Suprime-Cam (HSC) and a combination of new and existing spectroscopy. We select EELGs on the basis of substantial excess flux in the z broad band, which is sensitive to H α at 0.3 ≲ z ≲ 0.42 and [O iii ] λ 5007 at 0.7 ≲ z ≲ 0.86. We identify 10,470 galaxies with z excesses in the COSMOS data set and 91,385 in the NEP field. We cross-reference the COSMOS EELG sample with the zCOSMOS and DEIMOS 10k spectral catalogs, finding 1395 spectroscopic matches. We made an additional 71 (46 unique) spectroscopic measurements with Y < 23 using the HYDRA multiobject spectrograph on the WIYN 3.5 m telescope, and 204 spectroscopic measurements from the DEIMOS spectrograph on the Keck II telescope, providing a total of 1441/10,470 spectroscopic redshifts for the EELG sample in COSMOS (∼14%). We confirm that 1418 (∼98%) are H α or [O iii ] λ 5007 emitters in the above stated redshift ranges. We also identify 240 redshifted H α and [O iii ] λ 5007 emitters in the NEP using spectra taken with WIYN/HYDRA and Keck/DEIMOS. Using broadband-selection techniques in the g − r − i color space, we distinguish between H α and [O iii ] λ 5007 emitters with 98.6% accuracy. We test our EELG selection by constructing H α and [O iii ] λ 5007 luminosity functions and comparing to recent literature results. We conclude that broadband magnitudes from HSC, the Vera C. Rubin Observatory, and other deep optical multiband surveys can be used to select EELGs in a straightforward manner. 

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4. Large-scale Overdensity of Lyman Break Galaxies around the z = 6.3 Ultraluminous Quasar J0100 + 2802

   https://doi.org/10.3847/1538-4357/ad488a  

   Pudoka, Maria; Wang, Feige; Fan, Xiaohui; Yang, Jinyi; Champagne, Jaclyn; Jones, Victoria; Bian, Fuyan; Cai, Zheng; Jiang, Linhua; Liu, Dezi; et al (June 2024, The Astrophysical Journal)

   Abstract We study the environment of thez= 6.33 ultraluminous quasar SDSS J010013.02+280225.8 (J0100) to understand its association with large-scale structure. Theoretical models propose high-redshift quasars as markers of galaxy overdensities residing in the most massive dark matter halos (DMHs) in the early Universe. J0100 is an ultraluminous quasar with the most massive black hole known atz≳ 6, suggesting a high likelihood of residing in a massive DMH. We present wide-field (∼522 arcmin²) imaging in ther,i, andzbands from the Large Binocular Cameras on the Large Binocular Telescope, withY-andJ-band imaging from the Wide-field Infrared Camera on the Canada–France–Hawaii Telescope, centered on J0100. Applying color selections, we identify 23 objects asi-dropout Lyman break galaxy (LBG) candidates in the J0100 field. We use the deep photometric catalog in the 1.27 deg²COSMOS field to calculate the density of LBGs in a blank field, and to estimate the selection completeness and purity. The observed surface density of LBG candidates in the J0100 field corresponds to a galaxy overdensity ofδ= 4 (at 8.4σ). This large-scale overdensity suggests that the ∼22 arcmin²overdensity found by Kashino et al. using JWST data extends out to much larger scales. We calculate the angular autocorrelation function of the candidates and find a positive correlation on ≲10′ scales as well as evidence of asymmetries in their spatial distribution, further suggesting the direct detection of large-scale structure in the field of the ultraluminous quasar J0100. 

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5. Blobs and Blurs: A Citizen Science-identified Catalog of Diffuse Galaxies in the Fornax Cluster

   https://doi.org/10.3847/1538-4357/ae736d  

   Mazziotti, Nicolas; Jones, Michael G; Khim, Donghyeon J; Sand, David J; Bennet, Paul (July 2026, The Astrophysical Journal)

   Abstract We present a catalog of 643 diffuse galaxies identified through a citizen science search of the Fornax cluster, of which we estimate 21.8% are nucleated (139/637; 6 inconclusive). This marks the first crowd-sourced effort to construct a cluster-scale census of diffuse galaxies. These objects were visually identified using a combination of the Fornax Deep Survey and Dark Energy Camera Legacy Survey imaging across 26 deg². Over 1400 volunteers cataloged the candidates within this sky area at a rate of 1.15 days deg⁻². Our catalog is highly complete relative to existing dwarf catalogs of Fornax (>80% of objects recovered) down to an effective radiusr_eff = 5″, the minimum size we suggested volunteers classify, and to an effectiver-band surface brightness as faint as 〈μ_r〉 ≃ 26 mag arcsec⁻². We detect 97 candidates that existing automated searches of Fornax did not find, and three candidates not found by any prior search, automated or visual. The stellar mass distribution of our sample is consistent with similar dwarf studies of Fornax, with the nucleated fraction peaking at 80% for a host galaxy mass of ∼10^8.5M_⊙. The efficiency and completeness of our catalog thus establishes citizen science as a valuable tool for mapping diffuse galaxy populations in future sky surveys, such as the Legacy Survey of Space and Time. 

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