The Habitable Worlds Observatory (HWO) is a future NASA flagship mission concept identified by the Astro2020 Decadal Survey as the highest priority for large space missions. HWO should conduct "transformative astrophysics" and search for biosignatures in the atmospheres of approximately 25 potentially Earth-like planets. To further the early-stage development of HWO, NASA formed the Science, Technology, Architecture Review Team (START). In turn, START invited the scientific community to join working groups to explore the potential discovery space. In this paper, we present 70 science cases that resulted from this process. The cases address four scientific pillars: growth of galaxies (15 cases), evolution of the elements (13 cases), solar systems in context (32 cases), and living worlds (10 cases). Combined, they would address 27 of the 30 science questions and discovery areas identified by Astro2020. The 140 observing programs needed for the 70 investigations encompass a rich variety of spectroscopic (for 87

The Hobby-Eberly Dark Energy Experiment (HETDEX) is an untargeted similar to 540 deg(2) spectroscopic survey of Ly alpha emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1 sigma Ly alpha sensitivities of similar to 2-5 & times; 10(-18) erg s(-1) cm (-2)arcsec(-2) , allowing large samples of extended Ly alpha nebulae (LAN) to be studied. We selected a sample of 70,691 Ly alpha-emitting galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Ly alpha emission as a point-source component with an optional exponential envelope. Half (similar to 47.5%) of the LAE sample (33,612 objects) exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Ly alpha flux and luminosity. Their isophotal areas range from 10 to 130 arcsec(2) (median 15 arcsec(2)), with integrated Ly alpha fluxes from 6 to 2000 & times; 10-17 erg s-1 cm-2 (median 20 & times; 10-17 erg s-1 cm-2). Comparison between point-spread function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates the total Ly alpha flux by similar to 30% on average, reflecting the substantial halo contribution in extended sources. Approximately 420 LANs are found per deg(2) over 79.5 deg(2) of noncontiguous sky. About 12% of resolved sources show active galactic nuclei signatures and are bright in Ly alpha and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Ly alpha flux or luminosity (median 11.6 +/- 1.9 kpc). Only 2.9% of the full S/N > 6 LAE population with ancillary data have radio counterparts, but 64% of those are found to be extended, with the radio fraction increasing with Ly alpha size. We present a catalog of all modeled sources, with their positions, redshifts, luminosities, and structural parameters for over 70,000 LAEs consisting of 33,000 spatially extended LAN. The catalog can be found at https://hetdex.org/data-results/ and in the online version of this paper.

We present here the current state of a collection of promising ultraviolet technologies in preparation for the Habitable Worlds Observatory. Working with experts representing a significant number of groups working in the ultraviolet, we summarize some of the leading science drivers, present an argument for a 100-nm blue wavelength cutoff, and gather the current state of the art of UV technologies. We present the state of the art of contamination control, a crucial piece of the UV instrument plan. We explore next steps with individual technologies, as well as present paths forward with system-level testing and development.

We investigate extended Ly alpha emission using integral-field unit (IFU) data from the Hobby-Eberly Telescope Dark Energy Experiment (or HETDEX). We apply the modified Shepard method to image 106,853 Ly alpha emitters (LAEs) and median-stack them as functions of rest-frame Ly alpha equivalent width (EW), Ly alpha line flux, and redshift to obtain accurate flux measurements for the faintest Ly alpha detections. After careful consideration of point-spread function, centroiding, IFU correlation, and signal-to-noise ratio errors, we calculate that the one-dimensional exponential scale lengths of our LAEs range from similar to 3.0 to 7.1 kpc. The scale lengths show a slight negative correlation with the Ly alpha EW, with lower-EW sources having higher scale lengths. We also detect positive correlations between the scale length of the sample and its Ly alpha flux and luminosity within flux- and luminosity-binned subsamples. Overall, we find evidence for a decrease in Ly alpha halo size with increasing redshift. We discuss the mechanisms that could be powering these halos and driving their complex evolution.

We present the case for imaging ultraviolet line emission from highly ionized metals and HI Lya in the circumgalactic medium of galaxies, should the Hubble Space Telescope receive an orbital boost. Hubble can uniquely probe emission lines with ionization potentials between 13 and 200 electron-volts (Lya, CIV, OVI, NeVIII, etc). Spatial mapping of the diffuse material traced by these transitions is critical to constraining the physics of feedback and the energetic exchange between galaxies and their circumgalactic environments, as well as basic morphologies of the dominant mass component. Deep high-resolution mapping of these features will not be possible with any other observatory, existing or planned, until HWO is launched, which leaves HST as a critical observatory to test key science drivers for HWO. If HST receives an orbital boost, it can (a) provide the first statistical constraints on the spatial distribution of warm-hot CGM and (b) provide important avenues for science case development, as well as target/pointing selection, for HWO's upcoming spectroscopic facilities.

The circumgalactic medium (CGM) – the multiphase gas reservoirs surrounding galaxies – remains the least understood component of the baryon cycle governing galaxy growth, despite its central role in the Astro2020 Decadal Survey's priorities. Existing constraints come almost exclusively from pencil-beam absorption spectroscopy, leaving the spatial structure, kinematics, and phase interactions of CGM gas fundamentally unmapped. We present Ardua, a mission concept for NASA's ASTRA Initiative that combines wide-field far-ultraviolet spectroscopy with a Line Emission Mapper (LEM)-derived X-ray microcalorimeter instrument to obtain the first comprehensive emission maps spanning the full CGM temperature range, including cool neutral gas, ionized warm-hot phase gas, and the volume-filling hot corona. By observing more than 50 nearby galaxies comprehensively in the UV and X-ray, Ardua will test competing galaxy formation models, resolve multiphase gas flows and feedback-driven outflows, and extend baryon-cycle science to the intergalactic medium and the environments of exoplanet-hosting stars. Beyond its core CGM/IGM program, Ardua's wide-field, high-sensitivity instruments are designed to serve as a flexible community resource, supporting guest-investigator science across astrophysics. No planned or approved mission is designed to deliver this combined UV/X-ray survey capability.

The Sloan Digital Sky Survey V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multiepoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multiobject spectroscopy (MOS) at telescopes in both hemispheres (the 2.5 m Sloan Foundation Telescope at Apache Point Observatory and the 100-inch du Pont Telescope at Las Campanas Observatory), where 500 zonal robotic fiber positioners feed light from a wide-field focal plane to an optical (R similar to 2000, 500 fibers) and a near-infrared (R similar to 22,000, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra-wide-field (similar to 4000 deg(2)) integral field spectroscopy enabled by a new dedicated facility (LVM-I) at Las Campanas Observatory, where an integral field spectrograph (IFS) with 1801 lenslet-coupled fibers arranged in a 0 degrees.5-diameter hexagon feeds multiple R similar to 4000 optical spectrographs that cover 3600-9800 angstrom. SDSS-V's hardware and multiyear survey strategy are designed to decode the chemodynamical history of the Milky Way and tackle fundamental open issues in stellar physics in its Milky Way Mapper program, trace the growth physics of supermassive black holes in its Black Hole Mapper program, and understand the self-regulation mechanisms and the chemical enrichment of galactic ecosystems at the energy injection scale in its Local Volume Mapper program. The survey is well timed to multiply the scientific output from major all-sky space missions. The SDSS-V MOS programs began robotic operations in 2021; IFS observations began in 2023 with the completion of the LVM-I facility. SDSS-V builds on decades of heritage of SDSS's pioneering advances in data analysis, collaboration spirit, infrastructure, and product deliverables in astronomy.

Ground-based telescopes require useful and productive instruments to stay relevant in astronomy. The Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS), originally on the Kitt Peak National Observatory (KPNO) Mayall 4 m Telescope, is a long-slit and multi-object, low-resolution spectrograph. KOSMOS was acquired by the Astrophysical Research Consortium (ARC) for the Apache Point Observatory (APO) ARC 3.5 m telescope, implemented redesigns to the instrument, and renamed KOSMOS II. The instrument was integrated into the ARC 3.5 m's operational environment by adding a Nasmyth port adapter, a cart with a truss for mechanical support, and telescope user interface (TUI) software. Upgrades include slit-viewing guiding, internal calibration lamps, heat exhaust, and a new cryostat. Since 2021, KOSMOS II has proven capable of the high-throughput, low-resolution spectroscopy required by the ARC 3.5 m user community. This paper describes the design updates and revisions made to the instrument along with measurements of its performance. (C) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI:10.1117/1.JATIS.11.1.015003]

Here we present an automated method for obtaining wavelength calibrations for one-dimensional spectra, using Dynamic Time Warping (DTW). DTW is a flexible and well-understood algorithm for pattern matching, which has not been widely used in astronomy data analysis. Employing a calibrated template spectrum as a reference, DTW can recover non-linear and even discontinuous dispersion solutions without an initial guess. The algorithm is robust against differing spectral resolution between the template and sample data, and can accommodate some spurious or missing features. We demonstrate the effectiveness of DTW in an automated data reduction workflow, using both simulated and real arc lamp spectra in a Python data reduction framework. Finally, we provide a discussion on the utility and best practices with the DTW algorithm for wavelength calibration. We also introduce the PyKOSMOS data reduction toolkit, which includes our DTW calibration methods.

We present Maratus-a proposed 12U cubesat far ultraviolet narrow-band imager, centered on 1350 angstrom to map the circumgalactic medium (CGM). We primarily target O vi emission, likely the brightest tracer of the 10(5) - 10(6) K gas surrounding galaxies, at z similar to 0.3. Combining flight-proven hardware with recent technological improvements, we tackle one of the most interesting questions bridging large scale structure and galaxy evolution in our current moment - "How does gas flow into and out of g alaxies?" Answering t his question i s c rucial f or understanding the regulation of star formation, and the flow o f m atter, e nergy, a nd m etals t ravelling b etween g alaxies and the intergalactic medium. Maratus is a proof of principle instrument that will pave the way for large-scale mapping of the intergalactic medium. Mapping the CGM is identified a s a k ey d iscovery a rea i n t he recent astrophysics decadal report. By using COS-Halos galaxies for our targeted survey, we present the first opportunity to characterize a key metal tracer of the CGM in both emission and absorption.

By combining newly obtained deep Green Bank Telescope 21 cm observations with optical spectroscopic data, we present an analysis of the gas content of break bulges in red disks (breakBRD) galaxies, a population denoted by their blue star-forming centers and red quenched disks that do not appear to follow the typical inside-out evolution of spiral galaxies. We confirm previous results that the neutral atomic hydrogen (H i ) gas fractions of breakBRDs are, on average, lower than those of typical galaxies on the star-forming sequence (SFS), and find that their H i fractions are generally higher than green valley (GV) galaxies. H i depletion times for breakBRDs are roughly an order of magnitude lower than those of SFS galaxies, in stark contrast with GV galaxies that typically have much longer depletion times than SFS galaxies. The nuclear gas-phase metallicities of breakBRDs have a broader distribution than SFS galaxies and are skewed toward slightly above-average values. BreakBRDs are systematically offset from the baryonic Tully–Fisher relation toward lower baryonic mass at a given rotation velocity. They also have higher typical H i asymmetries than SFS galaxies, and of those galaxies with spatially resolved gas velocity fields from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey, two-thirds are either highly distorted or completely misaligned relative to the stellar disk. Evidence supports a scenario where breakBRDs are in an early phase of quenching, and there is mixed evidence that their behavior is related to past merger activity.

The National Aeronautics and Space Administration's (NASA) Great Observatories Maturation Program (GOMAP) will advance the science definition, technology, and workforce needed for the Habitable Worlds Observatory (HWO) with the goal of a phase A start by the end of the current decade. GOMAP offers long-term cost and schedule savings compared with the "technology readiness level (TRL) 6 by preliminary design review" paradigm historically adopted by large NASA missions. Many of the key technologies in the development queue for HWO require the combined activities of (1) facility and process development for validation of technologies at the scale required for HWO and (2) deployment in the "real-world" environment of mission integration and test prior to on-orbit operations. We present a concept for the SmallSat Technology Accelerated Maturation Platform (STAMP), an integrated facility, laboratory, and instrument prototype development program that could be supported through the GOMAP framework and applied to any of NASA's future Great Observatories (FGOs). This brief describes the recommendation for the first entrant into this program, "SmallSat Technology Accelerated Maturation Platform-1 (STAMP-1)," an ESPA Grande-class mission advancing key technologies to enable the ultraviolet capabilities of HWO. STAMP-1 would advance new broadband optical coatings, high-sensitivity ultraviolet detector systems, and multi-object target selection technology to TRL 6 with a flight demonstration. STAMP-1 advances HWO technology on an accelerated timescale, building on current research opportunities in space and earth sciences (ROSES) strategic astrophysics technology (SAT) + astrophysics research and analysis (APRA) programs, reducing cost and schedule risk for HWO while conducting a compelling program of preparatory science and workforce development with direct benefits for HWO mission implementation in the 2030s.

We present here the ongoing initial design for Ocotillo, a new fiber optic spectrograph being designed and built for the Apache Point Observatory 3.5m. Ocotillo is an fiber-fed optical spectrograph, with an interchangable front end allowing either a close-packed IFU with a 20 arcsecond field of view or a 16 robotic positioner system with integral field units on each positioner. Ocotillo, the new intermediate resolution spectrograph for the ARC 3.5m at Apache Point Observatory, provides a much needed update to the optical spectroscopic capabilities of this important mid-sized telescope. With a 9 arcminute field of view, the 3.5m creates opportunities for studying targets across the field as well as focusing efforts on more local central objects where spatially resolved spectroscopic coverage can reveal details of physical processes. The current suite of instruments is comprised of a wide field optical imager, two optical spectrographs (a low resolution long slit and an echelle), two infrared instruments (a spectrograph and an imager/Fabry-Perot spectrometer), and a high-speed optical time-domain camera photometer.

NASA's Great Observatories Maturation Program (GOMAP) will advance the science definition, technology, and workforce needed for the Habitable Worlds Observatory (HWO) with the goal of a Phase A start by the end of the current decade. GOMAP offers long-term cost and schedule savings compared to the 'TRL 6 by Preliminary Design Review' paradigm historically adopted by large NASA missions. Many of the key technologies in the development queue for HWO require the combined activities of 1) facility and process development for validation of technologies at the scale required for HWO and 2) deployment in the 'real world' environment of mission Integration Test prior to on-orbit operations. We present a concept for the Smallsat Technology Accelerated Maturation Platform (STAMP), an integrated facility, laboratory, and instrument prototype development program that could be supported through the GOMAP framework and applied to any of NASA's Future Great Observatories (FGOs). This brief describes the recommendation for the first entrant into this program, "STAMP-1", an ESPA Grande-class mission advancing key technologies to enable the ultraviolet capabilities of HWO. STAMP-1 would advance new broadband optical coatings, high-sensitivity ultraviolet detector systems, and multi-object target selection technology to TRL 6 with a flight demonstration. STAMP-1 advances HWO technology on an accelerated timescale, building on current ROSES SAT+APRA programs, reducing cost and schedule risk for HWO while conducting a compelling program of preparatory science and workforce development with direct benefits for HWO mission implementation in the 2030s.

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, Ly α S/N restricted stack of 50,000 HETDEX LAEs shows the ensemble biweight average z ∼ 2.6 LAE to be a blue (UV continuum slope ∼ −2.4 and E(B – V) < 0.1), moderately bright ( M UV ∼ −19.7) star-forming galaxy with strong Ly α emission (log L Ly α ∼ 42.8 and W λ (Ly α ) ∼ 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 0.2–0.3 Z ⊙ .

Supernova (SN) 2023ixf was discovered on May 19th, 2023. The host galaxy, M101, was observed by the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) collaboration over the period April 30, 2020 -- July 10, 2020, using the Visible Integral-field Replicable Unit Spectrograph (VIRUS; $3470\lesssim\lambda\lesssim5540$ \r{A}) on the 10-m Hobby-Eberly Telescope (HET). The fiber filling factor within $\pm$ 30 arcsec of SN 2023ixf is 80% with a spatial resolution of 1 arcsec. The r<5.5 arcsec surroundings are 100% covered. This allows us to analyze the spatially resolved pre-explosion local environments of SN 2023ixf with nebular emission lines. The 2-dimensional (2D) maps of the extinction and the star-formation rate (SFR) surface density ($\Sigma_{\rm SFR}$) show weak increasing trends in the radial distributions within the r<5.5 arcsec regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r<3 arcsec are $E(B-V)=0.06\pm0.14$, and $\Sigma_{\rm SFR}=10^{-5.44\pm0.66}~\rm M_{\odot}\cdot yr^{-1}\cdot arcsec^{-2}$. There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the $R_{23}$ calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity ($\sim Z_{\odot}$). The archival deep images from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the $z$-band at $22.778\pm0.063$ mag, but non-detections in the remaining four bands of CFHTLS ($u,g,r,i$). The results suggest a massive progenitor of $\approx$ 22 $M_\odot$.

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 .