Compound threats—two or more relatively rare and high-consequence events that co-occur in time and space, amplifying their effects—present difficult-to-predict events that can impose potentially grave consequences. While there has been increasing attention placed on modeling the probabilities and outcomes of compounding threats, there are no proposed governance models for compound threats, limiting the ability of policymakers and decisionmakers to manage such crises in the future. We visualize resilience for compound threats to understand how critical functioning and system utility to contain hazards, to absorb losses, and to recover from stressors shifts over time. Using North Carolina as a case study, we conduct a compound threats assessment for disaster risk to showcase its effectiveness in more accurately predicting disaster risk areas, as well highlight the limitations of existing risk models used by policymakers. We propose a resilience-augmented conceptual framework to rethink risk governance for compound threats that allows for speed (specifically flexibility and adaptability) in situations of high uncertainty while working within the rigid, slow-moving boundaries of government and bureaucracy. Finally, we discuss strategies for key actors to apply a resilience-augmented governance approach to compound threats into operational decision-making during crisis situations.
21 July 2022 in Monthly Notices of the Royal Astronomical Society
Global, radial, and local photometric measurements of several nearby low-mass galaxies are presented. Multiwavelength observations are used to trace the distributions of old and young stars, with the help of far-ultraviolet (FUV) to mid-infrared spectral energy distributions to derive star formation histories (SFHs). In addition to the surface brightness profiles, catalogues of UV-selected sources are created to better understand regions of galaxies with recent star formation. The clustering of these UV sources are studied in the dwarf irregular UGC 08188 (IC 4182) using a two-point correlation function. We find that the reddest of these UV sources are not clustered on any scale, but the bluer sources are clustered on scales approximately less than 1 kpc. We also find a possible negative radial gradient in the SFH parameter that marks the beginning of the younger stellar population’s formation (tburst) when analysing the entire sample of 3165 UV sources found across a total of 34 galaxies, giving quantitative evidence for the inside-out growth of galactic discs – a natural consequence of galaxy evolution in a Λ cold dark matter universe.
27 May 2021 in Monthly Notices of the Royal Astronomical Society
We have fit the far-ultraviolet to mid-infrared spectral energy distributions (SEDs) for several nearby galaxies (<20 Mpc). Global, radial, and local photometric measurements are explored to better understand how SED-derived star formation histories (SFHs) and classic star formation rate tracers manifest at different scales. Surface brightness profiles and radial SED fitting provide insight into stellar population gradients in stellar discs and haloes. A double exponential SFH model is used in the SED fitting to better understand the distributions of young versus old populations throughout these galaxies. Different regions of a galaxy often have undergone very different SFHs, either in strength, rate, timing, or some combination of all these factors. An analysis of individual stellar complexes within these galaxies shows a relationship between the ages of stellar clusters and how these clusters are distributed throughout the galaxy. These star formation properties are presented alongside previously published H i observations to provide a holistic picture of a small sample of nearby star-forming galaxies. The results presented here show that there is a wide variety of star formation gradients and average stellar age distributions that can manifest in a ΛCDM universe.
We present results from wide-field imaging of the resolved stellar populations of the dwarf spheroidal galaxies Cassiopeia III (And XXXII) and Perseus I (And XXXIII), two satellites in the outer stellar halo of the Andromeda galaxy (M31). Our WIYN pODI photometry traces the red giant star population in each galaxy to ∼2.5−3 half-light radii from the galaxy center. We use the tip of the red giant branch (TRGB) method to derive distances of (m − M)0 = 24.62 ± 0.12 mag (839 kpc, or kpc from M31) for Cas III and 24.47 ± 0.13 mag (738 kpc, or 351 kpc from M31) for Per I. These values are consistent within the errors with TRGB distances derived from a deeper Hubble Space Telescope study of the galaxies’ inner regions. For each galaxy, we derive structural parameters, total magnitude, and central surface brightness. We also place upper limits on the ratio of neutral hydrogen gas mass to optical luminosity, confirming the gas-poor nature of both galaxies. We combine our data set with corresponding data for the M31 satellite galaxy Lacerta I (And XXXI) from earlier work and search for substructure within the RGB star populations of Cas III, Per I, and Lac I. We find an overdense region on the west side of Lac I at a significance level of 2.5σ–3σ and a low-significance filament extending in the direction of M31. In Cas III, we identify two modestly significant overdensities near the center of the galaxy and another at two half-light radii. Per I shows no evidence for substructure in its RGB star population, which may reflect this galaxy’s isolated nature.
1 November 2026 in The Astrophysical Journal Supplement Series
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.