Simon C. O. Glover

Context . Multi-wavelength surveys place cloud dispersal at ∼1–5 Myr after massive-star emergence, before the first core-collapse supernovae. Whether a cloud disperses, re-collapses, or leaks Lyman-continuum (LyC) photons depends on how pre-supernova winds, radiation pressure, and photoionised gas pressure ( P _{H II} ) couple to the swept-up shell. Aims . We introduce T RINITY , a 1D thin-shell code that succeeds WARPFIELD and follows stellar feedback across varied initial cloud structures. Methods . T RINITY evolves the bubble-shell structure under winds, supernovae, direct and dust-reprocessed radiation pressure, P _{H II} , and gravity. A phase-aware driving prescription uses higher values of the hot-bubble and photoionised gas pressures in the energy-driven phase and accounts for P _{H II} and direct ram pressure in the momentum-driven phase. The initial cloud may be uniform, a piecewise power law, or a Bonnor-Ebert sphere. Shell structure, hot-bubble cooling, photon absorption, and LyC escape are solved alongside the dynamics. Results . We validated the code against analytic wind and photoionisation limits and explored runs with cloud masses M _cloud = 10 ⁵ –10 ^6.5 M _⊙ , core densities n _core = 10 ³ –10 ⁴ cm ⁻³ , and star-formation efficiencies ε = 0.01–0.30. Including P _{H II} increases the bubble radius by ∼10% at 10 Myr in the fiducial validation run. In a higher-efficiency example, the energy-driven phase lasts on the order of 1 Myr, radiation pressure remains subdominant, and P _{H II} remains dynamically significant after the transition to momentum-dominated evolution. Density structure changes both phase durations and outcomes. At fixed M _cloud , n _core , and ε , homogeneous and shallow profiles re-collapse, while a steep ρ ∝ r ⁻² cloud keeps expanding. In a dispersing grid, Bonnor-Ebert clouds reach their dispersal time ( τ _disp ) much later than homogeneous clouds. Conclusions . The first results show that both P _{H II} and cloud structure are important for a complete dynamical treatment: P _{H II} alters late-time shell expansion, and density structure shifts dispersal thresholds and emergence times for a fixed stellar population. T RINITY provides an efficient framework for mapping feedback dominance across a cloud parameter space and produces the diagnostics needed to compare with resolved H II region observations.

We present a multiwavelength analysis of a young bubble in the nuclear starburst of NGC 253 using new JWST MIRI–MRS observations together with archival ALMA (100, 350, 690 GHz) and Chandra data. The MIRI maps reveal a prominent bubble-like structure in both ionized and molecular emission lines. The bubble is spatially coincident with one of the least embedded massive young clusters detected with ALMA, suggesting that the cluster is driving the expansion. We measure a radius of ∼11.5 ± 3.4 pc and an expansion velocity of ∼90 ± 44 km s ⁻¹ , implying a dynamical age of ∼0.1 ± 0.1 Myr. Using RADEX modeling of multiple CO transitions, we infer a molecular mass in the range of (1.3 ± 0.3) × 10 ⁴ to (2.8 ± 0.8) × 10 ⁵ M _⊙ . We derive a kinetic energy on the order 10 ⁵¹⁻⁵² erg, consistent with mechanical input from Wolf–Rayet stellar winds or supernovae in a ∼10 ⁶ M _⊙ cluster. The existence of a large population of Wolf–Rayet stars or past supernovae is supported by the presence of coincident X-ray emission. Our results provide direct evidence that individual clusters in a nuclear environment can carve out coherent structures on parsec scales and inject significant energy and momentum into the surrounding interstellar medium, which can contribute to the nuclear outflow in NGC 253.

Using JWST/MIRI imaging of M51 in eight broadband filters, we investigate correlations of mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) and dust continuum with molecular, atomic, and ionized gas traced by ¹² CO (1–0), H i , and Pa α , respectively. In molecular-gas-dominated regions, PAH-dominated filters (F560W, F770W, F1130W, F1280W) exhibit near-linear correlations with ¹² CO (1–0) at ∼40 pc scale, indicating that PAHs are well mixed with gas and experience relatively constant radiation field intensities. The F1500W, F1800W, and F2100W dust-continuum-dominated filters show shallower slopes, with ¹² CO (1–0) reflecting contributions from star-forming regions with high radiation field intensities. This is reinforced by the near-linear scaling between F2100W and Pa α . PAH-dominated bands do not show this linear trend with Pa α , likely due to their destruction in ionized regions. F1000W behaves similarly to PAH bands in its correlations with ¹² CO (1–0) and Pa α . Modeling mid-infrared emission with an empirical decomposition into gas- and star-formation-associated components shows that PAH-dominated filters receive comparable contributions from both, while the relative contribution associated with the Pa α template increases toward longer wavelengths, reaching ∼75% in F2100W. These results demonstrate that mid-infrared simultaneously traces the gas column and star formation, but with a systematic wavelength-dependent shift in what drives the correlations—PAHs being more gas-tracing and dust continuum reflecting star formation. Lastly, considering both H i and H ₂ at ∼440 pc resolution, we find a tight, approximately linear relation between Σ HI + H 2 and PAH-dominated filters. Although most of our coverage is in H ₂ -dominated regions, we note similar observations with H i , suggesting that PAHs are also well mixed with atomic gas.

The central molecular zone (CMZ) resides in the inner few hundred parsecs of our Galaxy, and despite being the largest reservoir of dense molecular gas in the Milky Way, it has a relatively low present-day star formation rate (SFR) of ∼0.08 M _⊙ yr ⁻¹ . Continuum and spectral line observations from the Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey (ACES) provide the first full-coverage, high-resolution map of the inner 200 pc of the CMZ at 3 mm. In this paper we present the ACES catalog of compact continuum sources, the most complete catalog of potential sites of star formation in the CMZ to date. Using an automated dendrogram-based source extraction procedure in combination with a by-eye morphological classification scheme, we produce a “full” catalog of 1735 detections in total. Additionally, we use spectral index measurements to generate a “filtered” catalog of 567 sources with minimal contamination from nonthermal filaments and extended free–free emission. We find that 359 (∼63%) of the filtered catalog sources are located at column densities 23 cm ⁻² , outside of the densest molecular cloud regions, 195 of which have not been identified in previous surveys. After cross-referencing with various catalogs generated from data at different wavelengths, we consider it likely that many of these newly discovered detections are produced by pre-/protostellar sources or compact H ii regions.

We present the largest study to date of star cluster mass and age distributions in nearby galaxies. The analysis is based on a uniformly selected catalog of over 15,000 (36,000) human- (machine-) classified compact clusters across 38 spiral galaxies in the PHANGS-Hubble Space Telescope survey, with improved photometric SED age dating that mitigates key degeneracies with reddening and metallicity. The galaxies span a factor of ∼100 in star formation rate (SFR) and in their surface density of star formation and molecular gas (Σ _SFR , Σ H 2 ), and cover a broad range of morphologies. We find that cluster mass functions are well described by a power law, dN / dM ∝ M ^β , with β = −1.9 ± 0.2, and that this shape is remarkably similar across all galaxies in our sample and eight composite groups of galaxies with similar SFRs, with no significant dependence on SFR, Σ _SFR , or Σ H 2 . Cluster age distributions decline steeply and can be described by dN / dτ ∝ τ ^γ with γ = −0.83 ± 0.24, again with little dependence on host-galaxy properties or cluster mass. The independence of the mass and age distributions implies a separable joint distribution, g ( M , τ ) ∝ M ^β τ ^γ , and suggests that cluster populations in spiral disks are dominated by strong, mass-independent dissolution over their first approximately gigayear. These results establish a benchmark for interpreting cluster demographics across diverse galactic environments and provide context for studies of young cluster populations at high redshift.

We present 50–100 pc-resolution JWST/MIRI and NIRCam measurements of mid-infrared (mid-IR) color variations in the diffuse interstellar medium (ISM) of 71 nearby star-forming galaxies from the PHANGS-JWST survey. Mid-IR emission traces the dust column density, intensity ( U ) and hardness of the interstellar radiation field, and the physical state (charge, size) and abundance of polycyclic aromatic hydrocarbons (PAHs). Mid-IR colors that trace PAH band ratios remain fairly constant in the diffuse ISM of star-forming disks. However, they show stark variations in extreme environments: highly star-forming central molecular zones (CMZs) and star formation deserts/quiescent bulges. In CMZs, PAH-to-continuum (3.3/21, 7.7/21, and 11.3/21 μ m) and the 10/21 μ m continuum colors are 0.2–0.4 dex lower than in normal disks. We attribute this to higher U based on the far-infrared dust colors and the high 21 μ m/Σ _Mol , which we suggest to be a good tracer of U outside star-forming regions. Meanwhile, star formation deserts show low 7.7 μ m PAH emission, resulting in low 7.7/21 μ m and 7.7/11.3 μ m, while all other mid-IR colors remain typical. This suggests the presence of more neutral PAHs in star formation deserts, where low 7.7 μ m likely reflects ISM conditions similar to early-type and elliptical galaxies. All environments form part of a continuous trend in 7.7/11.3 μ m versus specific star formation rate.

Recent observations by the James Webb Space Telescope (JWST) have found evidence for an invariant relation between stellar mass, metallicity, and star formation rate up to z ∼ 8 and its breakdown at higher redshifts. Understanding the underlying physics driving such correlations is thus crucial. Here, we explore the impact of the initial mass function (IMF) on the chemical evolution of high-redshift galaxies. Indeed, star formation and metal enrichment in galaxies are regulated by supernova (SN) explosions and metal yields from massive stars, which are sensitive to the high-mass end of the IMF. Using the semi-analytical galaxy evolution code a-sloth , we follow galactic baryon cycles along merger trees built from a high-resolution cosmological simulation. Stellar feedback is modeled with up-to-date stellar evolution tracks covering the full metallicity range ( Z ∼ 10 ⁻¹¹ –0.03) and a broad stellar mass range ( m _⋆ ∼ 2–600 M _⊙ ), including metal yields from stellar winds, core-collapse SNe, (pulsational) pair-instability SNe, and Type Ia SNe. Assuming a Kroupa-like IMF with a varying upper mass limit m max , we find that only models with m max ≳ 200 M ⊙ can simultaneously reproduce the observed mass–metallicity–star formation rate relation and cosmic star formation history at z ≳ 4, owing to enhanced metal yields from pair-instability SNe. Our results confirm that very massive (≳200 M _⊙ ) stars and pair-instability SNe play an important role in the star formation and chemical enrichment histories of high- z galaxies. They also have profound implications for electromagnetic transients and gravitational-wave events.