Searcharxiv⌕ Search

arXiv subjects

Sarah M. Sweet

Publications and source records attributed to Sarah M. Sweet.

At least 19 recordsLinked to original sources
arXiv2026

The Delegate Survey: KOALA/AAOmega-IFU spectroscopy of three nearby dwarf galaxies

Assessing the cosmological typicality of the Local Group is crucial for establishing whether its dwarf galaxy population is representative. To this end, the Delegate Survey targets dwarf galaxies in Local Group analogues for systematic comparison. As a pilot study for the Delegate Survey, we obtained integral-field spectra of three dwarf galaxies, GAMA 79098, GAMA 569709, and HIPASS J1159-19 S2, in two nearby galaxy groups using the KOALA instrument on the AAT. The galaxies were mapped at a spatial sampling of 1.25 arcsec per spaxel, providing two-dimensional spectral coverage of both the stellar and ionised gas components. Using continuum and emission-line maps, we investigate the ionisation structure, star-forming properties, metallicity, star formation histories, and velocity fields of each system. GAMA 79098 exhibits properties closely analogous to the SMC, with ongoing star formation superimposed on an old stellar population and moderate rotational support. GAMA 569709 resembles transition-type Local Group (LG) dwarfs such as NGC 147 and NGC 185, showing predominantly an old stellar population. HIPASS J1159-19 S2 is dominated by young stars and intense star-forming complexes, consistent with a dynamically young, gas-rich galaxy group environment. The two GAMA dwarfs follow the LG stellar mass-metallicity relation within uncertainties, while HIPASS J1159-19 S2 appears approximately 0.5 dex more metal-rich for its stellar mass. Overall, the structural, chemical, and kinematic properties of these dwarfs overlap substantially with analogous LG dwarfs.

astro-ph.GA↗
arXiv2026

The MAGPI survey: Stellar population radial trends and mass assembly in star-forming galaxies at z~0.3

The evolution of galaxies from cosmic noon to the present day provides a key window to probe the balance between early, rapid bulge formation and prolonged disk growth. The epoch at $z \sim 0.3$ marks a crucial transitional phase between the peak of cosmic star formation and the predominantly quiescent local Universe. In this work, we examine the spatially resolved stellar populations of 34 galaxies at $z \sim 0.3$ to quantify radial gradients in age, stellar metallicity, and star formation activity, and disentangle the distinct evolutionary pathways of inner and outer galactic components. We utilise MUSE integral-field spectroscopy data cubes from the MAGPI survey at redshifts of $0.28 < z < 0.35$. Stellar population properties are derived using the spectral synthesis codes FADO and Starlight, and radial profiles are constructed by fitting isophotal annuli to the galaxy continuum emission. We further reconstruct star formation histories and cumulative mass assembly curves for inner and outer regions. We find pronounced negative radial gradients in age and negative to flat gradients in stellar metallicity. Inner regions are systematically older and more metal-rich than their surrounding outskirts, with age differences up to 3-4 Gyr in the most massive systems. H$α$ equivalent width profiles reveal centrally suppressed specific star formation in most galaxies. Star formation histories and mass assembly curves demonstrate that galaxy cores formed $80\%$ of their stellar mass rapidly, within the first 2-3 Gyr of cosmic time; while areas outside $\mathrm{1\,R_{eff}}$ assembled more gradually and sustained star formation to later epochs. Outskirts evolve primarily through extended, secular star formation, establishing the centrally concentrated quenching and inside-out growth that link high-redshift systems to the quiescent galaxies of the local Universe.

astro-ph.GA↗
arXiv2026

The Mysterious Case of Iron in XMPs: Anomalous High log(Fe/O) Observed in Extremely Metal-Poor Galaxies HSCJ1631+4426 and SDSSJ0811+4730

We present integral field spectroscopic observations of two local extremely metal-poor galaxies (XMPs), HSCJ1631+4426 and SDSSJ0811+4730, obtained with the Keck Cosmic Web Imager (KCWI) over the wavelength range $3545-5529$ Å at a spectral sampling of 0.5 Å, capturing bright nebular emission lines essential for determining gas-phase metallicity and chemical enrichment measurements. Using integrated spectra, we derive oxygen abundances of $\rm12+\log(O/H)=7.079\pm0.010$ and $6.926\pm0.004$, and elevated Fe/O ratios of $\rm\log(Fe/O)=-1.57\pm0.17$ and $-1.28\pm0.07$, for HSCJ1631+4426 and SDSSJ0811+4730 respectively. Each galaxy is fully contained within the $\sim$8'' field of view, with 0.15'' spaxels providing spatially resolved information. These measurements indicate unusually efficient iron enhancement at extremely low metallicity; Fe/O ratios approach or exceed solar despite oxygen abundances of only $\sim$2% solar, inconsistent with enrichment from core-collapse supernovae alone or delayed Type Ia supernovae given the young ages of the systems. Comparison with chemical evolution models suggests rare, highly energetic explosions such as bright hypernovae and/or pair-instability supernovae are likely responsible. Our results reinforce the growing evidence that XMPs can reflect the nucleosynthetic processes of early energetic stellar explosions, serving as local laboratories for chemical enrichment pathways prevalent in the early Universe.

astro-ph.GA↗
arXiv2026

The MAGPI Survey: Evidence for Non-Universal Resolved Dust Attenuation Relations Beyond the Local Universe

We study the spatially resolved relation between dust attenuation ($A_V$) and star formation rate surface density ($Σ_{\mathrm{SFR}}$) in galaxies from the MAGPI survey ($0.25 < z < 0.42$). Using Balmer-decrement-based attenuation maps for 178 galaxies, we investigate whether the locally calibrated resolved $A_V$--$Σ_{\mathrm{SFR}}$ relation remains valid at intermediate redshift by comparing MAGPI with the local relation measured from MaNGA. We find a clear positive correlation between $A_V$ and $Σ_{\mathrm{SFR}}$ in MAGPI, with systematically higher attenuation than in MaNGA at fixed $Σ_{\mathrm{SFR}}$. After matching galaxies in stellar mass ($M_{*}$) and offset from the star-forming main sequence ($Δ$SFMS), MAGPI galaxies remain more attenuated than MaNGA galaxies at fixed $Σ_{\mathrm{SFR}}$. The attenuation excess is strongest for galaxies below the SFMS ($ΔA_V \sim 0.40$ mag), weaker for galaxies on the SFMS ($ΔA_V \sim 0.28$ mag), and minimal for galaxies above the SFMS ($ΔA_V \sim 0.07$ mag). The dependence of the offset on $Δ$SFMS suggests that nebular attenuation on kpc scales is regulated not only by local star formation activity, but also by the global evolutionary state of the host galaxy. Together, these results indicate that the resolved $A_V$--$Σ_{\mathrm{SFR}}$ relation is not universal, and that locally calibrated attenuation relations may not fully describe galaxies at intermediate redshift. This highlights the need for attenuation calibrations that account for galaxy population and redshift when interpreting spatially resolved galaxy properties.

astro-ph.GA↗
arXiv2026

Hector Galaxy Survey: Optical IFU and Chandra Reveal a Low-Luminosity AGN Behind Extended LINER Emission

We present evidence that the Hector Galaxy Survey galaxy C901005481609968 ($z_{\rm cl}=0.0553$), which exhibits spatially extended LINER-like emission in optical integral-field spectroscopy (IFS), hosts a low-luminosity active galactic nucleus (LLAGN) that contributes substantially to its ionization budget. Although the galaxy is not selected as an AGN by mid-infrared AGN color criteria, archival Chandra data reveal a compact nuclear X-ray source with $\log L_{\rm X}\approx41.46$ erg/s, supporting the presence of an LLAGN. Spatially resolved emission-line diagnostics show LINER-like line ratios across most spaxels with $\mathrm{S/N} \geq 3$, while spatially resolved $τ$ maps ($τ\equiv Q_{\rm pAGB}/Q_{\rm req}$) indicate a widespread photon deficit ($\logτ<0$ over most of the mapped region), even under the most optimistic pAGB normalizations, the nuclear region remains at $τ< 1$. Line-ratio--kinematic tests find no evidence for shock-dominated excitation as the primary driver of the extended emission, although a localized or sub-dominant shock contribution cannot be ruled out with the present data. We use this galaxy as a pilot case because the combination of Hector IFS and an independent nuclear X-ray constraint provides a stringent validation of the spatially resolved photon-budget framework. Our results indicate that evolved stellar populations alone cannot account for the observed emission, that an additional nuclear ionizing source is required at least in the inner region, and that a weak LLAGN likely contributes to the ionizing budget, particularly in the inner region. Our results demonstrate that extended LINER-like emission can conceal a substantial LLAGN contribution even when traditional optical and infrared AGN indicators are weak, and that spatially resolved photon-budget tests combined with X-ray constraints can effectively reveal such hidden activity.

astro-ph.GA↗
arXiv2026

A Census of Double-Peaked Lyman-alpha Emitters in MAGPI: Classification, Global Characteristics, and Spatially Resolved Properties

Double-peaked Ly$α$ profiles provide critical insights into gas kinematics and the distribution of neutral hydrogen (HI) from the interstellar to the intergalactic medium (ISM to IGM), and serve as valuable diagnostics of ionising Lyman continuum (LyC) photon escape. We present a study of the global and spatially resolved properties of double-peaked Ly$α$ emitters (LAEs) based on VLT/MUSE data from the MAGPI survey. From a parent sample of 417 LAEs at z = 2.9 - 6.6 in the first 35 fields, we identify 108 double-peaked LAEs using an automated peak classification technique. We measure a double-peak fraction of $\sim37\%$ at $z < 4$, decreasing to $\sim14\%$ at $z > 4$, likely due to enhanced IGM attenuation. Approximately $17\%$ of the double-peaked LAEs are blue-dominated, possibly tracing gas inflows, though backscattering remains a viable alternative for sources without systemic redshift. The blue-to-total flux ratio exhibits a luminosity dependence: fainter lines generally show higher blue flux. We find a narrowing of the red peak at $z > 4$, despite the presence of the blue peak, indicating intrinsic galaxy evolution rather than IGM attenuation. Several LAEs exhibit residual flux in the absorption trough, with normalised trough flux anticorrelating with peak separation, reflecting variations in HI column density. We further investigate spatially resolved properties of ten red-dominated LAEs with extended Ly$α$ halos. Despite azimuthal variations, both the blue-to-total flux ratio and normalised trough flux density increase with radius, while peak separation decreases. The red peak asymmetry shows only minor radial changes. These trends are consistent with variations in shell outflow velocity and HI column density across the halos. Based on peak separation, red peak asymmetry, and residual trough flux, we identify five LAEs as strong LyC-leaker candidates.

astro-ph.GA↗
arXiv2026

Large-scale and local environmental drivers of quenching: tracing H$α$ concentration in X-ray and optical galaxy groups

To explore the environmental mechanisms causing quenching in nearby star-forming galaxies, we study the variation with local and large-scale environments of a star formation concentration index, C-index $\equiv\log{(r_{50,{\rm H}α}/r_{50,\rm cont}})$, that traces the spatially-resolved distribution of H$α$ emission. Our analysis combines (i) GAMA spectroscopic redshift survey data to optically select galaxy groups and reconstruct the cosmic web, (ii) eROSITA data to identify X-ray-emitting groups, and (iii) SAMI Galaxy Survey data to characterise spatially-resolved star formation. We find that galaxies in X-ray+optical groups exhibit the lowest median C-index and the highest fraction of centrally-concentrated star-forming galaxies relative to optical groups and the field (independently of group or stellar mass). Star-forming galaxies in more X-ray luminous groups at fixed dynamical mass show more concentrated star formation. At large scales, nodes show the lowest median C-index and the highest fraction of centrally-concentrated star-forming galaxies relative to filaments and voids, which have similar C-index distributions. C-index correlates most strongly with the distance to the closest node, leaving no significant role for other local or large-scale environment metrics. Finally, regular star-forming galaxies tend to have spins aligned parallel to filaments, consistent with smooth gas accretion, while centrally-concentrated galaxies tend have spins aligned perpendicular to filaments, likely driven by mergers and associated with bulge growth. These results suggest that multi-scale environmental processes, i.e. locally and at large-scale, act to concentrate star formation toward galaxy centres, via gas-related mechanisms in nodes and ram-pressure stripping in X-ray+optical groups.

astro-ph.GA↗
arXiv2026

Multi-band Reconstruction of Sixteen Gravitational Lens Systems using PISCO data

Next-generation surveys such as the Euclid survey, the Legacy Survey of Space and Time (LSST), and the China Space Station Telescope (CSST) survey are expected to discover ~10^5 galaxy-galaxy scale strong gravitational lenses. This motivates the development of scalable and robust lens modeling approaches that can efficiently and reliably learn from wide-field survey datasets before high-resolution follow-up. We design a scalable, Bayesian, Lenstronomy-based pipeline and apply it to a sample of sixteen lens candidates observed with the Parallel Imager for Southern Cosmology Observations (PISCO) on the Magellan telescope. PISCO provides four-band imaging (z, i, r, g) with colours, depth and seeing conditions comparable to LSST. To fully exploit the constraining power of this dataset, our pipeline performs simultaneous multi-band modeling, using a common mass profile across all four bands while allowing independent light profiles in each. This approach leverages color information to provide joint constraints on the lens mass and yields reduced uncertainties compared to single-band analyses. Fifteen out of sixteen PISCO lens candidates are successfully recovered with interpretable lensing configurations, including DESJ0533-2536, the first reported hyperbolic-umbilic galaxy-galaxy scale strong lensing candidate. We further assess how much model complexity can be reliably constrained given the resolution and seeing of PISCO-like data. Overall, our results demonstrate that scalable, multi-band lens modeling of ground-based data can extract meaningful constraints on mass and source morphology, providing a practical pathway to maximize the scientific return from large samples in upcoming surveys.

astro-ph.GA↗
arXiv2026

The MAGPI Survey: co-evolution of baryons and dark matter in star-forming disk-like galaxies at $0.1 \lesssim z \lesssim 0.85$

We present a comprehensive analysis of the dark matter (DM) content and its structural dependence in star-forming disk-like galaxies at intermediate redshifts ($0.1 \lesssim z \lesssim 0.85$), utilizing spatially resolved kinematic data from the MAGPI survey. We report the following: (1) Low stellar mass galaxies ($M_{\rm star} < 10^{9.5}\, M_\odot$) are strongly DM dominated across all radii, with average $\langle f_{_{\rm DM}} \rangle \sim 0.85$, while high-mass ($M_{\rm star} > 10^{10.5}\, M_\odot$) systems exhibit relatively low DM fractions in their inner regions ($\langle f_{_{\rm DM}} \rangle \sim 0.47$) which is equivalent to local massive disk galaxies (e.g., Milky Way and Andromeda). This suggests a mass-dependent structural dichotomy, most-likely governed by a combination of internal galactic processes and environmental influences. (2) A tight inverse correlation between $f_{_{\rm DM}}$ and baryon mass surface density ($Σ_{\rm bar}$), with intrinsic scatter of $\sim 0.11$ dex. This is consistent with an inside-out baryon assembly scenario and suggests that the fundamental structural correlations of galaxies were already established by $z\sim 0.85$. (3) No significant evolution in $f_{_{\rm DM}}$ with redshift across the MAGPI window, and when combined with higher-redshift ($0.6 \leq z \leq 1.5$) data from Sharma et al. 2025, we quantitatively show that the reported decline in $f_{_{\rm DM}}(z)$ is most-likely due to observational biases against low-mass systems at $z > 1$. These results offer empirical evidence for a scenario in which disk-like galaxies evolve through a co-regulated build-up of baryonic and DM components, preserving internal structural regularities (such as the total mass distribution and rotation-curve shape) throughout cosmic time.

astro-ph.GA↗
arXiv2025

The MAGPI Survey: forward modelled gas-phase metallicity gradients in galaxies at $z\sim 0.3$

We measure the seeing-deconvolved gas-phase metallicity gradients of 70 star-forming galaxies at $z\sim 0.3$ 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 $\nabla \mathrm{[O/H]}=-0.013^{+0.059}_{-0.033}$ dex/kpc. Among the galaxies in our sample, 32.9% have negative metallicity gradients (2$σ$ significance), 10.0% have positive gradients and 57.1% have flat gradients. The $\nabla \mathrm{[O/H]}$-$M_*$ 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 $\nabla \mathrm{[O/H]}$ and gas velocity dispersion ($r=0.36$), 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.

astro-ph.GA↗
arXiv2025

Constraining Cosmology with Double-source-plane Strong Gravitational Lenses from the AGEL Survey

Double-source-plane strong gravitational lenses (DSPLs), with two sources at different redshifts, are independent cosmological probes of the dark energy equation of state parameter $w$ and the matter density parameter $Ω_{\rm m}$. We present the lens model for the DSPL AGEL035346$-$170639 and infer cosmological constraints from this system for flat $Λ$ cold dark matter and flat $w$CDM cosmologies. From the joint posterior of $w$ and $Ω_{\rm m}$ in the flat $w$CDM cosmology, we extract the following median values and 1$σ$ uncertainties: $w = -1.52^{+0.49}_{-0.33}$ and $Ω_{\rm m} = 0.192^{+0.305}_{-0.131}$ from AGEL0353 alone. Combining our measurements with two previously analyzed DSPLs, we present the joint constraint on these parameters from a sample of three, the largest galaxy-scale DSPL sample used for cosmological measurement to date. The combined precision of $w$ from three DSPLs is higher by 15% over AGEL0353 alone. Combining DSPL and cosmic microwave background (CMB) measurements improves the precision of $w$ from CMB-only constraints by 39%, demonstrating the complementarity of DSPLs with the CMB. Despite their promising constraining power, DSPLs are limited by sample size, with only a handful discovered so far. Although ongoing and near-future wide-area sky surveys will increase the number of known DSPLs by up to two orders of magnitude, these systems will still require dedicated high-resolution imaging and spectroscopic follow-ups like those presented in this paper. Our ASTRO 3D Galaxy Evolution with Lenses collaboration is undertaking such follow-up campaigns for several newly discovered DSPLs and will provide cosmological measurements from larger samples of DSPLs in the future.

astro-ph.CO↗
arXiv2025

The coherent satellite velocity field around the interacting spiral galaxy pair NGC5713/19: signature of two galaxy groups merging

The luminous spirals NGC5713 and NGC5719 form an interacting galaxy pair 94 kpc apart and are connected by a straight, elongated neutral hydrogen structure extending over 200 kpc. Their 14 velocity-confirmed satellite galaxies and the two hosts separate into two distinct subgroups in their line-of-sight velocities and on-sky distribution revealing a prominent coherent kinematic structure with a velocity amplitude of 67+-12 kms-1 . We test four scenarios to explain the observed velocity field: isotropic motions in a dark matter halo, a plane of satellites seen nearly face-on, and a kinematically mixed satellite system with a co-rotating edge-on plane and an isotropic component, and a merger of two small galaxy groups. Taking the geometry and dynamical state of the NGC5713/19 pair into account together with their positions and motions in the Bootes Strip the most consistent picture is the infall of two satellite systems that follow their host galaxies along a cosmic filament. We believe this is the first clear example of an equal-mass L* disk galaxy merger where a kinematically coherent satellite system is in the process of formation. These observations reinforce the importance of major mergers as a channel for producing co-rotating satellite systems.

astro-ph.GA↗
arXiv2025

Reevaluating UMa3/U1: star cluster or the smallest known galaxy?

Ursa Major III/UNIONS 1 (UMa3/U1) is the faintest Milky Way satellite discovered to date, exhibiting a half-light radius of 3 $\pm$ 1 pc and an absolute V-band magnitude of +2.2 $\pm$ 0.4. Previous studies suggest UMa3/U1 is a dwarf galaxy, based on its large internal velocity dispersion and the improbability (indicated by dynamical cluster simulations) of its long-term survival if it were a dark-matter-free star cluster. In this paper, we model the evolution of UMa3/U1 as a star cluster using collisional N-body simulations that include a description of stellar evolution and the external tidal field of the Milky Way, with some simulations including primordial binaries. We find that UMa3/U1 has a substantial remaining lifetime of 2.7 $\pm$ 0.4 Gyr, primarily due to the retention of compact stellar remnants within the cluster. This retention is facilitated by mass segregation and the preferential loss of low-mass stars. Furthermore, we demonstrate that the observed large velocity dispersion of UMa3/U1 can be successfully reproduced. These results support the possibility that UMa3/U1 is a self-gravitating star cluster. Our simulations reveal that modelling UMa3/U1 as a dark matter free star cluster produces a markedly altered present-day mass function, driven by a strong depletion of low-mass stars. However, the degree of mass segregation among the visible stars is not statistically significant. We therefore recommend that future observations of UMa3/U1 and other very small Milky Way satellites focus on measuring their present-day mass functions to determine their nature.

astro-ph.GA↗
arXiv2025

Cosmography with the Double Source Plane Strong Gravitational Lens AGEL150745+052256

Strong gravitational lenses with two background sources at widely separated redshifts are a powerful and independent probe of cosmological parameters. We can use these systems, known as Double-Source-Plane Lenses (DSPLs), to measure the ratio ($β$) of angular-diameter distances of the sources, which is sensitive to the matter density ($Ω_m$) and the equation-of-state parameter for dark-energy ($w$). However, DSPLs are rare and require high-resolution imaging and spectroscopy for detection, lens modeling, and measuring $β$. Here we report only the second DSPL ever used to measure cosmological parameters. We model the DSPL AGEL150745+052256 from the ASTRO 3D Galaxy Evolution with Lenses (AGEL) survey using HST/WFC3 imaging and Keck/KCWI spectroscopy. The spectroscopic redshifts for the deflector and two sources in AGEL1507 are $z_{\rm defl}=0.594$, $z_{\rm S1}=2.163$, and $z_{\rm S2}=2.591$. We measure a stellar velocity dispersion of $σ_{\rm obs}=109 \pm 27$ km s$^{-1}$ for the nearer source. Using $σ_{\rm obs}$ for the main deflector (from literature) and S1, we test the robustness of our DSPL model. We measure $β=0.953^{+0.008}_{-0.010}$ for AGEL1507 and infer $Ω_{\rm m}=0.33^{+0.38}_{-0.23}$ for $Λ$CDM cosmology. Combining AGEL1507 with the published model of the Jackpot lens improves the precision on $Ω_{\rm m}$ ($Λ$CDM) and w (wCDM) by $\sim 10 \%$. The inclusion of DSPLs significantly improves the constraints when combined with Plancks cosmic microwave background observations, enhancing precision on w by $30 \%$. This paper demonstrates the constraining power of DSPLs and their complementarity to other standard cosmological probes. Tighter future constraints from larger DSPL samples discovered from ongoing and forthcoming large-area sky surveys would provide insights into the nature of dark energy.

astro-ph.CO↗
arXiv2025

The AGEL Survey Data Release 2: A Gravitational Lens Sample for Galaxy Evolution and Cosmology

The ASTRO 3D Galaxy Evolution with Lenses (AGEL) Survey is an ongoing effort to spectroscopically confirm a diverse sample of gravitational lenses with high spatial resolution imaging, to facilitate a broad range of science outcomes. The AGEL systems span single galaxy-scale deflectors to groups and clusters, and include rare targets such as galaxy-scale lenses with multiple sources, lensed quiescent galaxies, and Einstein rings. We build on the 77 systems presented in Tran et al. 2022 (AGEL data release 1) to present a total 138 lenses, and high resolution F140W and F200LP Hubble Space Telescope images for 71 lenses from a completed HST SNAP program. Lens candidates were originally identified by convolutional neural networks in the DES and DECaLS imaging fields, and of the targets with follow-up spectroscopy we find a high (96%) success rate. Compared with other spectroscopic lens samples, AGEL lenses tend to have both higher redshift deflectors and sources. We briefly discuss the common causes of false-positive candidates, and strategies for mitigating false-positives in next generation lens searches. Lastly, we present 6 galaxy-scale double-source plane lenses useful for cosmological analyses. With next-generation telescopes and surveys such as Euclid, Vera Rubin's Legacy Survey of Space and Time, Keck Observatory's KAPA program, and 4MOST's 4SLSLS surveys on the horizon, the AGEL survey represents a pathfinder for refining automated candidate search methods and identifying and triaging candidates for followup based on scientific potential.

astro-ph.GA↗
arXiv2025

The MAGPI Survey: the subtle role of environment and not-so-subtle impact of generations of stars on galaxy dynamics

The stellar age and mass of galaxies have been suggested as the primary determinants for the dynamical state of galaxies, with environment seemingly playing no or only a very minor role. We use a sample of 77 galaxies at intermediate redshift (z~0.3) in the Middle-Ages Galaxies Properties with Integral field spectroscopy (MAGPI) Survey to study the subtle impact of environment on galaxy dynamics. We use a combination of statistical techniques (simple and partial correlations and principal component analysis) to isolate the contribution of environment on galaxy dynamics, while explicitly accounting for known factors such as stellar age, star formation histories and stellar masses. We consider these dynamical parameters: high-order kinematics of the line-of-sight velocity distribution (parametrised by the Gauss-Hermite coefficients $h_3$ and $h_4$), kinematic asymmetries $V_{\rm asym}$ derived using kinemetry and the observational spin parameter proxy $λ_{R_e}$. Of these, the mean $h_4$ is the only parameter found to have a significant correlation with environment as parametrised by group dynamical mass. This correlation exists even after accounting for age and stellar mass trends. Finally, we confirm that variations in the spin parameter $λ_{R_e}$ are most strongly (anti-)correlated with age as seen in local studies, and show that this dependence is well-established by z~0.3.

astro-ph.GA↗
arXiv2024

The MAGPI Survey: radial trends in star formation across different cosmological simulations in comparison with observations at $z \sim$ 0.3

We investigate the internal and external mechanisms that regulate and quench star formation (SF) in galaxies at $z \sim 0.3$ using MAGPI observations and the EAGLE, Magneticum, and IllustrisTNG cosmological simulations. Using SimSpin to generate mock observations of simulated galaxies, we match detection/resolution limits in star formation rates and stellar mass, along with MAGPI observational details including the average point spread function and pixel scale. While we find a good agreement in the slope of the global star-forming main sequence (SFMS) between MAGPI observations and all three simulations, the slope of the resolved SFMS does not agree within 1 $-$ 2$σ$. Furthermore, in radial SF trends, good agreement between observations and simulations exists only for galaxies far below the SFMS, where we capture evidence for inside-out quenching. The simulations overall agree with each other between $\sim1.5-4 \ R_{\rm e}$ but show varying central suppression within $R \sim 1.5 \ R_{\rm e}$ for galaxies on and below the SFMS, attributable to different AGN feedback prescriptions. All three simulations show similar dependencies of SF radial trends with environment. Central galaxies are subject to both internal and external mechanisms, showing increased SF suppression in the centre with increasing halo mass, indicating AGN feedback. Satellite galaxies display increasing suppression in the outskirts as halo mass increases, indicative of environmental processes. These results demonstrate the power of spatially resolved studies of galaxies; while global properties align, radial profiles reveal discrepancies between observations and simulations and their underlying physics.

astro-ph.GA↗