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Abstract:

Abstract We analyse the assembly history of the edge-on lenticular galaxy NGC 3957 using deep integral-field spectroscopic MUSE data from the GECKOS survey. By applying a dust-corrected Multi-Gaussian Expansion and a population-orbit superposition model, we disentangle the galaxy’s stellar kinematics, age, and metallicity. We dynamically decompose the galaxy and identify three distinct components: a dynamically-cold main disc, a compact Nuclear Stellar Disc (NSD), and a hot component. The NSD emerges as the youngest and most metal-rich component (t = 6.9 ± 0.4 Gyr; [Z/H] = 0.49 ± 0.06 dex), implying that the stellar bar is a long-lived structure that formed at least ~7 Gyr ago. The main stellar disc is dynamically cold (σz ~ 20 − 30 km/s), precluding any significant mergers over the last ~8 Gyr, and exhibits a strong positive age gradient (younger inside, older outside) beyond the bar radius. Synthesising these dynamical fossil records, NGC 3957 likely evolved as a ‘faded spiral’ in a small-to-medium group environment. Its outer disc might passively fade due to mild gas starvation, while the bar fuelled prolonged central star formation. Comparison with S0s in the Fornax cluster reveals that this combination of internal secular evolution and mild starvation produces ‘outside-in’ fading signatures that could mimic the environmental stripping typically seen in dense clusters.

Abstract:

We measure the seeing-deconvolved gas-phase metallicity gradients of 70 star-forming galaxies at from the MAGPI survey and investigate their relationship with galaxy properties to understand the mechanisms that influence the distribution of metals and shape the evolution of the galaxies. We use a Bayesian modelling technique, blobby3d, which accounts for seeing effects (beam smearing) and can model the substructures of the flux distribution. The median metallicity gradient of our sample is dex kpc−1. Among the galaxies in our sample, 32.9 per cent have negative metallicity gradients (2 significance), 10.0 per cent have positive gradients and 57.1 per cent have flat gradients. The – relation of the MAGPI galaxies generally agrees with theoretical predictions, where a combination of stellar feedback, gas transport, and accretion shapes the metallicity profile, with the dominant processes varying with galaxy mass. We find a positive correlation between and gas velocity dispersion (), indicating that stronger gas turbulence is associated with flatter or inverted metallicity gradients, likely due to enhanced gas mixing. Additionally, smaller galaxies tend to have flatter or positive gradients, suggesting that metal dilution by gas accretion or removal via feedback-driven winds may outweigh metal enrichment in small galaxies.

Abstract:

The central regions of disc galaxies host a rich variety of stellar structures: nuclear discs, bars, bulges, and boxy-peanut bulges. These components are often difficult to disentangle, both photometrically and kinematically, particularly in star-forming galaxies where dust obscuration and complex stellar motions complicate interpretation. In this work, we used data from the GECKOS-MUSE survey to investigate the impact of dust on axisymmetric Jeans Anisotropic Multi-Gaussian Expansion (JAM) models and assess their ability to recover kinematic structures in edge-on disc galaxies. We constructed JAM models for a sample of seven edge-on ( i ⪆ 85°) galaxies that span a range of star formation rates, dust content, and kinematic complexity. We find that when dust is appropriately masked, the disc regions of each galaxy are fit to χ reduced 2 ≤ 5. We analysed 2D residual velocity fields to identify signatures of non-axisymmetric structure. We find that derived dynamical masses are constant within 10% for each galaxy across all dust masking levels. In NGC 3957, a barred boxy galaxy in our sample, we identified velocity residuals that persist even under aggressive dust masking, aligned with bar orbits and supported by photometric bar signatures. We extended this analysis to reveal a bar in IC 1711 and a possible side-on bar in NGC 0522. Our results highlight both the capabilities and limitations of JAM in dusty, edge-on systems and attempt to link residual velocities to known non-axisymmetric kinematic structure.

Abstract:

We present a dynamical and chemical study of the centre of a massive early-type strong-lens galaxy ESO 286−G022 (SNL-1). Analysing new data obtained through the adaptive-optics-assisted Narrow-Field Mode of Very Large Telescope/Multi-Unit Spectroscopic Explorer, we aim to measure the mass distribution and internal properties of SNL-1 at resolution. In particular, we aim to address the tension in the reported initial mass function (IMF) measurements of SNL-1 between strong-lens/dynamical and spectral-fitting techniques. We fit a triaxial orbital dynamical model to the measured stellar kinematics, including constraining the mass of the (resolved) central supermassive black hole. The dynamical model is consistent with the mass-to-light ratio expected for a Kroupa-like IMF. We also employ a highly flexible spectral-fitting technique, which instead favours a Salpeter-like IMF (low-mass slope ) over the same spatial region. To conclude, we discuss possible origins of this discrepancy, both intrinsic and technical.