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Abstract:

We present the PHANGS-MUSE/HST-H α nebulae catalogue, comprising 5177 spatially resolved nebulae across 19 nearby star-forming galaxies ( D < 20 Mpc), based on high-resolution H α imaging from HST, homogenised to a fixed (10 pc) physical resolution and sensitivity. Combined with MUSE integral field spectroscopy, this enables robust classification of 4882 H  II regions and the separation of planetary nebulae and supernova remnants. We derive electron densities for 2544 H  II regions using [S  II ] diagnostics and adopt direct or representative electron temperatures for consistent physical characterisation. Nebular sizes are measured using circularised radii and intensity-weighted second moments, yielding a median radius of approximately 20 pc and extending down to (sub-)parsec (deconvolved) radii. A structural complexity score is introduced via hierarchical segmentation to trace substructure, highlighting that around a third of the regions are H  II complexes containing several individual clusters and bubbles, with an increased fraction of these regions in galactic centres. A luminosity–size relation, calibrated using the resolved HST sample, is applied to 30 790 MUSE nebulae, allowing the recovery of nebular sizes down to ~1 pc and providing statistical completeness beyond the HST detection limit. Comparisons with classical Strömgren radii indicate that observed sizes are systematically larger, corresponding to typical volume filling factors with a median of ϵ ~ 0.22 (10th–90th percentile 0.06–0.78), with larger regions exhibiting progressively lower values. We associate 3349 H  II regions with stellar populations from the PHANGS-HST association catalogue, finding median ages of ~3 Myr and typical stellar masses of around 10 4 –10 5 M ⊙ , 91̽»¨ing the link between ionised nebular and young stellar populations. We also assess the impact of diffuse ionised gas on emission-line diagnostics and after removing confirmed supernova remnants, find no strong variation in line ratios with nebular resolution, indicating minimal systematic bias in the MUSE catalogue. This dataset establishes a detailed, spatially resolved connection between nebular structure and ionising sources, and provides a benchmark for future studies of feedback, DIG contributions, and star formation regulation in the ISM, especially in combination with matched high-resolution observations. The full catalogue is made publicly available in machine-readable format.

Abstract:

Abstract We re-analysed ALMA observations of the [O iii] λ88μm emission line in JADES-GS-z14-0, so one of the most distant spectroscopically confirmed galaxy at z=14.18. Our analysis shows a tentative detection of a velocity gradient of [O iii] λ88μm using three independent tests: (1) construction of moment maps; (2) extraction of integrated spectra from a grid of apertures; and (3) spectro-astrometry in both the image and uv planes, confirming the presence of the velocity gradient at 3σ significance. We performed kinematical fitting using the KinMS code and estimated a dynamical mass of log10(Mdyn/$\rm M_\odot$)= 9.4$^{+0.8}_{-0.4}$, with the bulk of the uncertainties due to the degeneracy between dynamical mass and inclination. We measure an upper limit on the velocity dispersion (σv) of <40 km s−1 which results in an estimate of Vrot/σ > 2.5. This result, if confirmed with higher-resolution observations, would imply that kinematically cold discs are already in place at z ∼ 14. Comparison with mock observations from the SERRA cosmological simulations confirms that even low-resolution observations are capable of detecting a velocity gradient in z > 10 galaxies as compact as JADES-GS-z14-0. This work shows that deeper ALMA or JWST/NIRSpec IFS observations with high spatial resolution will be able to estimate an accurate dynamical mass for JADES-GS-z14-0, providing an upper limit to the stellar mass of this over-luminous galaxy.

Abstract:

We present measurements of the masses associated with ∼18,​​​​​000 H ii regions across 19 nearby star-forming galaxies by combining data from JWST, Hubble Space Telescope, MUSE, Atacama Large Millimeter/submillimeter Array, Very Large Array, and MeerKAT from the multiwavelength PHANGS survey. We report 10 pc-scale measurements of the mass of young stars, ionized gas, and older disk stars coincident with each H ii region, as well as the initial and current mass of molecular gas, atomic gas, and swept-up shell material, estimated from lower-resolution data. We find that the mass of older stars dominates over young stars at ≳10 pc scales, and ionized gas exceeds the stellar mass in most optically bright H ii regions. Combining our mass measurements for a statistically large sample of H ii regions, we derive 10 pc-scale star formation efficiencies of ≈6%–17% for individual H ii regions. Comparing each region’s self-gravity with the ambient interstellar medium (ISM) pressure and total pressure from presupernova stellar feedback, we show that most optically bright H ii regions are overpressured relative to their own self-gravity and the ambient ISM pressure and that they are hence likely expanding into their surroundings. Larger H ii regions in galaxy centers approach dynamical equilibrium. The self-gravity of regions is expected to dominate over presupernova stellar feedback pressure at ≳130 and 60 pc scales in galaxy disks and centers, respectively, but is always subdominant to the ambient ISM pressure on H ii region scales. Our measurements have direct implications for the dynamical evolution of star-forming regions and the efficiency of stellar feedback in ionizing and clearing cold gas.