Joseph N. Burchett

Oxygen is forged by stars and redistributed through galaxies by feedback-driven outflows, leaving a record of star formation and the baryon cycle imprinted on its present-day abundance and distribution. The Galaxies Losing Oxygen via Winds project quantifies the production, distribution, and retention of oxygen in 37 low-mass, low–metallicity, gas-rich galaxies in the nearby Universe ( D < 6 Mpc) spanning a critical stellar mass range (10 ^6.5 < M _* < 10 ^9.5 ) where feedback is expected to strongly shape galaxy evolution. We incorporate literature results to extend the analysis over 10 ⁵ < M _* < 10 ^11.5 . We couple star formation histories derived from resolved stars with measurements of interstellar medium metallicity and gas mass, and compare the oxygen budgets with empirical constraints in the circumgalactic medium (CGM). We find low-mass galaxies retain between 4% and 25% (mean 11%) of their oxygen produced by stellar nucleosynthesis, and nearly all retained oxygen resides in the gas. Galaxies exhibit increased scatter to higher oxygen retention fractions when residing in denser environments (Θ ₅ > 0.5) and within 1 Mpc of a massive galaxy ( M _* > 10 ⁹ M _⊙ ), indicating the environment likely affects the amount of oxygen retained, recycled, or accreted to galaxies. Contrary to expectations, oxygen retention does not correlate with position on the mass–metallicity relation. Although ionized oxygen is detected in the CGM, it remains unclear whether most missing oxygen resides there or has been expelled entirely. Hydrodynamical simulations, despite successfully reproducing the mass–metallicity relation, predict much higher retention fractions than measured in low-mass galaxies. Simple modeling indicates that wind mass-loading and outflow metallicity govern oxygen retention, and that low-mass galaxies accrete less baryonic material relative to the cosmic baryon fraction.

Gas-rich, star-forming, low-mass galaxies in the nearby Universe are powerful laboratories for studying baryonic physics in detail, including: stellar mass assembly, stellar feedback, chemical enrichment, and the interplay of the interstellar medium with star formation. Investigating these disparate yet interconnected processes requires data obtained by myriad observatories. Here, we present a comprehensive atlas of uniformly processed data on 37 low-mass galaxies within 6 Mpc. The atlas includes archival data on (i) the H i from the Very Large Array observatory; (ii) resolved stars from Hubble Space Telescope optical imaging; (iii) Spitzer Space Telescope 3.6 μ m imaging; and (iv) optical imaging from ground-based telescopes. We also compile measurements of (i) tip-of-the-red-giant-branch (TRGB) distances to the galaxies; (ii) direct method gas-phase oxygen abundances and nitrogen-to-oxygen abundance ratios; (iii) constraints on the local environment around each galaxy; and (iv) other measurements from the literature. We supplement the data with new observations where needed to complete the measurements for all galaxies in the sample. From these data, we find good agreement between stellar masses measured from color–magnitude diagrams and those estimated from 3.6 μ m imaging by assuming a mass-to-light ratio. We also provide the first mapping of the H i profiles as a function of structural parameters. These data sets and measurements are the foundation for the Galaxies Losing Oxygen via Winds (GLOW) project, whose main aim is to characterize the star formation−chemical enrichment cycle of low-mass galaxies by measuring the production, distribution, and retention of oxygen on a galaxy-by-galaxy basis.

Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific “mappers”: the Milky Way Mapper, which aims to chart the various components of the Milky Way and constrain its formation and assembly; the Black Hole Mapper, which focuses on understanding supermassive black holes in distant galaxies across the Universe; and the Local Volume Mapper, which uses integral field spectroscopy to map the ionized interstellar medium in the Local Group. This paper describes the scope and content for the nineteenth data release (DR19) of SDSS, which is the most substantial to date in SDSS-V. DR19 is the first to contain data from all three mappers. Additionally, we also describe nine value-added catalogs that enhance the science that can be conducted with the SDSS-V data. Finally, we discuss how to access SDSS DR19 and provide illustrative examples and tutorials.

We leverage the IllustrisTNG cosmological simulations to test how the large-scale cosmic web shapes galaxy morphology and to forecast the early cosmic web structure that the Nancy Grace Roman Space Telescope will reveal. In the hydrodynamic TNG50 and N -body TNG50-Dark runs, we reconstruct the cosmic web at redshifts z = 0, 0.5, 1, 2, 3, and 4 with the Monte Carlo Physarum Machine density estimator and the DisPerSE structure identification framework. We confirm that dark matter halos start out predominantly prolate (elongated), and their shapes are aligned with their nearest filaments; prolate galaxies retain strong shape alignment with their outer halos to later times. At z ≥ 1, the fraction of prolate (spheroidal) halos increases (decreases) toward lower stellar mass, higher redshift, and lower filament density. At z < 1, more spheroidal (oblate) stellar structures preferentially reside in higher-density (lower-density) filaments. We also find that higher-density filaments favor extended rotationally supported disks, whereas lower-density filaments more often host smaller dispersion-supported systems. Then, generating mock galaxy samples from TNG100 and TNG50, we predict the early cosmic web accessible to Roman. We find that the spectroscopic emission-line depth planned for the High-Latitude Wide-Area Survey (HLWAS) yields a highly incomplete galaxy sample that does not accurately trace the z = 1 cosmic web. A survey ≥2.5× deeper over a few square degrees would enable a proper reconstruction and reveal qualitatively correct filament–galaxy morphology relationships. Nevertheless, the planned HLWAS Deep field should still identify most galaxy overdensities; targeted deeper spectroscopy of these regions would efficiently and adequately map the early filamentary structure.

High velocity clouds supply the Milky Way with gas that sustains star formation over cosmic timescales. Precise distance measurements are therefore essential to quantify their mass inflow rates and gauge their exact contribution to the Galaxy’s gas supply. We use a sample of 594 SDSS-V BOSS stellar spectra within 10° of the high-velocity Smith Cloud (SC) to trace Na I absorption and dust extinction as functions of distance. By fitting interstellar-medium-corrected MaStar templates to each spectrum, we isolate residual equivalent widths and extinction and then compare trends in the SC region to a same-latitude control field. Stars beyond 1 kpc toward the SC exhibit a significant Na I equivalent width excess (>0.2 Å, >3 σ ) relative to the control. Two-component linear fits of Na I equivalent width and A _V against both low and high-velocity H I column densities show that the low-velocity component is strongly correlated with both quantities, while the high-velocity term is marginally significant in extinction and Na I , consistent with a patchy, low dust-to-gas ratio. Given that the excess Na I begins at distances <2 kpc uniquely in the direction of the SC, and previous estimates of the SC place it at 12.4 ± 1.3 kpc, further investigation of its distance is warranted.

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 ∼ 2000, 500 fibers) and a near-infrared ( R ∼ 22,000, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra–wide-field (∼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 . ° 5-diameter hexagon feeds multiple R ∼ 4000 optical spectrographs that cover 3600–9800 Å. 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.

For half a century now, the galaxy formation and evolution community has recognized the critical role of gas accretion to sustain star formation (e.g., Refs. 1, 2). Gas is thought to transition into galaxies through accretion processes and, in turn, get expelled from galaxies through feedback processes, an interplay that regulates galactic gas content. What is now broadly called “feedback” includes the ejection of both matter and energy from stellar winds, radiation, and supernovae as well as active galactic nuclei (AGN), and both theory and observation have implicated feedback as central to regulating, perhaps even halting (or quenching), star formation. The discovery of a ubiquitous circumgalactic medium (CGM; Fig. 1) from quasar absorption line studies supports this paradigm: (1) the dark matter halos in which galaxies reside contain a substantial baryonic component well beyond any stellar extent of a galaxy (a potential source of fuel for star formation)⁴; (2) the gaseous halos permeating their dark matter counterparts are correlated with their host galaxy star formation properties (connecting the CGM to central galaxy activity)^5,6; (3) galaxy environment impacts the gas reservoirs of galaxies living in overdense environments such as groups and clusters (where quenched galaxies reside in great numbers)⁷; and (4) more than half of the metals in the universe reside outside galaxies, which implicates ejection from sites of star formation (galaxies) into the CGM.⁸

The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object 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$\sim 2000$, 500 fibers) and a near-infrared (R$\sim 22,000$, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra wide-field ($\sim$ 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 0.5 degree diameter hexagon feeds multiple R$\sim$4000 optical spectrographs that cover 3600-9800 angstroms. SDSS-V's hardware and multi-year survey strategy are designed to decode the chemo-dynamical history of the Milky Way Galaxy 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 upon decades of heritage of SDSS's pioneering advances in data analysis, collaboration spirit, infrastructure, and product deliverables in astronomy.

We present one of the largest uniform optical spectroscopic surveys of X-ray selected sources to date that were observed as a pilot study for the Black Hole Mapper (BHM) survey. The BHM program of the Sloan Digital Sky Survey (SDSS)-V is designed to provide optical spectra for hundreds of thousands of X-ray selected sources from the SRG/eROSITA all-sky survey. This significantly improves our ability to classify and characterise the physical properties of large statistical populations of X-ray emitting objects. Our sample consists of 13 079 sources in the eROSITA eFEDS performance verification field, 12 011 of which provide reliable redshifts from 0 ≲ z ≤ 5.8. The vast majority of these objects were detected as point-like sources (X-ray flux limit F_{0.5 − 2 keV} ≳ 6.5 × 10⁻¹⁵ erg/s/cm²) and were observed for about 20 years with fibre-fed SDSS spectrographs. After including all available redshift information for the eFEDS sources from the dedicated SDSS-V plate programme and archival data, we visually inspected the SDSS optical spectra to verify the reliability of these redshift measurements and the performance of the SDSS pipeline. The visual inspection allowed us to recover reliable redshifts (for 99% of the spectra with a signal-to-noise ratio of > 2) and to assign classes to the sources, and we confirm that the vast majority of our sample consists of active galactic nuclei (AGNs). Only ∼3% of the eFEDS/SDSS sources are Galactic objects. We analysed the completeness and purity of the spectroscopic redshift catalogue, in which the spectroscopic completeness increases from 48% (full sample) to 81% for a cleaner, brighter (r_AB < 21.38) sample that we defined by considering a high X-ray detection likelihood, a reliable counterpart association, and an optimal sky coverage. We also show the diversity of the optical spectra of the X-ray selected AGNs and provide spectral stacks with a high signal-to-noise ratio in various sub-samples with different redshift and optical broad-band colours. Our AGN sample contains optical spectra of (broad-line) quasars, narrow-line galaxies, and optically passive galaxies. It is considerably diverse in its colours and in its levels of nuclear obscuration.

We examine the redshift evolution of the relationship between the neutral atomic hydrogen (H i) content and star formation properties of blue galaxies, along with their location in the cosmic web. Using the COSMOS H i Large Extragalactic Survey (CHILES) and the IllustrisTNG (TNG100) cosmological simulation, and the DisPerSE algorithm, we identify the filamentary structure in both observations and simulations, measure the distance of galaxies to the nearest filament spine D _fil, and calculate the mean H i gas fraction and the relative specific star formation rate (sSFR) of blue galaxies in three different cosmic web environments—0 < D _fil/Mpc < 2 (filament cores), 2 < D _fil/Mpc < 4 (filament outskirts), and 4 < D _fil/Mpc < 20 (voids). We find that, although there are some similarities between CHILES and TNG, there exist significant discrepancies in the dependence of H i and star formation on the cosmic web and on redshift. TNG overpredicts the observed H i fraction and relative sSFR at z = 0–0.5, with the tension being strongest in the voids. CHILES observes a decline in the H i fraction from filament cores to voids, exactly the opposite of the trend predicted by TNG. CHILES observes an increase in H i fraction at z = 0.5 → 0 in the voids, while TNG predicts an increase in this time in all environments. Further dividing the sample into stellar mass bins, we find that the H i in log ( M * / M ⊙ ) > 10 galaxies is better reproduced by TNG than H i in log ( M * / M ⊙ ) = 9 − 10 galaxies.