arXiv subjects

Piyush Sharda

Publications and source records attributed to Piyush Sharda.

At least 19 recordsLinked to original sources

arXiv2026

ALMA Observations of DEM L241/LMC P3 in the Large Magellanic Cloud: Evidence for the Formation of Cool Molecular Jets Driven by a Microquasar

We present ALMA observations of DEML 241/LMC P3, the most luminous $\gamma$-ray binary consisting of a compact object and an O star, in CO emission. We have found an one-sided jet-like CO feature of 8 pc length and 1 pc width, which accompanies another weaker CO jet candidate with slightly different orientation. The one-sided CO jet exhibits striking alignment with LMC P3, suggesting that the jet was driven by LMC P3. We have determined kinetic temperature of the CO jet to be significantly high at 33$-$60 K as compared with $\sim$15 K in the nearby non-jet CO cloud whereas no radiative heat source is found. We interpret that the high temperatures are due to shock heating of a microquasar jet driven by the $\gamma$-ray binary, where the compact object has an accretion disk fed by the O star winds. The CO jet matches existing predictions from magneto-hydrodynamical simulations, which show that CO jet can form from the interaction of the microquasar jet and an ambient ISM cloud. These results provide strong evidence that CO jets are a signature sculptured by microquasar jets, lending support for mass accretion in LMC P3 as the $\gamma$-ray origin. The results suggest a second case of CO jets potentially driven by a microquasar along with the CO jets in the microquasar candidate HESS J1023-575 recently identified in the Milky Way. Further, our results suggest the use of sub-mm observations for identifying microquasars, opening a new possible window for their discovery and study.

astro-ph.HE↗

arXiv2026

REBELS-25: multi-phase morphology and kinematics at z = 7.31

We present a spatially resolved, multi-wavelength study of the massive, star-forming galaxy REBELS-25 at a redshift of $z=7.31$. We combine new high-resolution ALMA [O III]88$\mu$m observations with resolution-matched [C II], dust continuum, and JWST/NIRSpec IFU spectroscopy, providing a $\lesssim1$ kpc view of the morphology, interstellar medium (ISM) conditions, and multi-tracer gas kinematics of one of the most mature galaxies known in the reionisation era. We find differing morphologies from the rest-frame UV to far-infrared (FIR) emission, with the UV and optical emission appearing clumpy and irregular, whereas the FIR emission is well-described by near-exponential disc profiles, with [C II] being the most extended. Comparing the resolved UV and FIR emission, we find that obscured star formation contributes $\sim55$-$98$% of the total star formation rate across the galaxy, demonstrating that dust obscuration strongly shapes the observed UV and optical morphology. Resolved ionisation-line diagnostics show no significant variation across the source at $\sim1$ kpc resolution, consistent with broadly similar ISM conditions among the identified regions. Kinematic modelling reveals that both the warm ionised gas, traced by [O III]88$\mu$m, and the colder neutral gas, traced by [C II], share the same large-scale rotating structure and are dynamically cold, with ratios of ordered-to-random motion, $V/\sigma$, of $\sim11$ and 4.5, respectively, although we find evidence for non-circular motions that are not well-described by a simple rotating disc. Overall, these results further support a picture in which REBELS-25 hosts a dusty, chemically enriched, and dynamically cold ISM already in place at $z=7.31$.

astro-ph.GA↗

arXiv2026

AMReX-Astrophysics Microphysics: A set of microphysics routines for astrophysical simulation codes based on the AMReX library

The AMReX-Astrophysics Microphysics library provides a common set of microphysics routines (reaction networks and associated physics, equations of state, and various transport coefficients) as well as solvers (stiff ODE integrators, nonlinear system solvers) for astrophysical simulation codes built around the AMReX adaptive mesh refinement library (W. Zhang et al., 2019). Several multi-dimensional simulation codes, including the compressible hydrodynamics code Castro (Almgren et al., 2010), the low-Mach number hydrodynamics code MAESTROeX (Fan et al., 2019), and the radiation-hydrodynamics code Quokka (Wibking & Krumholz, 2022) use Microphysics to provide the physics and solvers needed to close the hydrodynamics systems that they evolve. The library is implemented in C++ with GPU-offloading a key design feature.

astro-ph.IM↗

arXiv2026

The evolution of the galaxy gas-phase mass-metallicity relation from $z=15$ to $z=0$ in the COLIBRE cosmological simulations

We present the evolution of the galaxy gas-phase mass-metallicity relation (MZR) from $z=15$ to $z=0$ in the COLIBRE cosmological hydrodynamical simulations. Amongst other novel features, COLIBRE follows the multiphase interstellar medium with gas allowed to cool to $\sim 10\,\mathrm{K}$, and includes a new chemistry model in which hydrogen and helium are tracked in non-equilibrium, metals are allowed to mix and diffuse, and the chemical network is coupled to a self-consistent live dust model. Using fiducial COLIBRE runs spanning particle masses from $10^5\,\mathrm{M_{\odot}}$ to $10^7\,\mathrm{M_{\odot}}$ and box sizes $25 - 400\,\mathrm{cMpc}$, we derive the median, mass-weighted MZRs for star-forming galaxies and compare them with a comprehensive compilation of observational data and other simulations. COLIBRE reproduces the observed MZR across cosmic time, notwithstanding the systematic uncertainties in observational measurements of the gas-phase oxygen abundances. The simulations show excellent numerical convergence and uniquely probe the full stellar mass range sampled by current observations across all redshifts. We find that the MZR is already in place at cosmic dawn ($z \approx 10$), and shows no evolution until $z \approx 5$. The slope of the MZR becomes shallower at low redshifts. The turnover at the high-mass end is largely governed by feedback from active galactic nuclei (AGN), whereas the low-mass end of the MZR sensitively depends on the strength of feedback from core collapse supernovae. Variations in the star formation efficiency or depletion of oxygen on dust grains have a more minor impact on the MZR. We identify key physical processes that shape the MZR across cosmic time and highlight where future observations can further constrain galaxy formation models.

astro-ph.GA↗

arXiv2026

Radiative Feedback in Population III Protostellar Growth: HI Shielding \& HII Region Trapping

We present a suite of radiation-magnetohydrodynamics simulations from the Popsicle project that follow the long-term growth ($\sim 50$ kyr) of primordial protostars while self-consistently coupling radiation, turbulence, and magnetic fields. The simulation suite is designed to quantify the relative impacts of the pathways of radiative feedback in Pop III stars -- the extreme-ultraviolet (EUV) ionization and Lyman-Werner (LW) dissociation -- by considering simulations with/without their inclusion. We find that without HI shielding, LW feedback can suppress and ultimately terminate accretion. With HI shielding, the large column densities near the protostar significantly weaken LW feedback. In the polar direction, atomic hydrogen fully shields LW radiation where H$_2$ self-shielding alone is insufficient. This leads to lower gas temperatures near the protostar and higher accretion rates, yielding larger final stellar masses than in models without shielding. The HII region remain confined, extending $\sim$100 AU beyond the sink accretion radius (75 AU), as dense gravitationally bound gas sustains high recombination rates and prevents sustained pressure-driven breakout. Turbulence and magnetic fields may also contribute to its confinement, even at high ionizing luminosities. These results demonstrate that the interplay of gas dynamics, shielding, and radiative feedback can significantly alter the growth of Pop III stars. We discuss the implications for the initial mass function of primordial stars and the influence of feedback from early stellar populations.

astro-ph.GA↗

arXiv2026

Hidden mass in early galaxies revealed by bottom-heavy initial mass functions

James Webb Space Telescope (JWST) observations have revealed that massive galaxies formed and evolved faster than predicted by galaxy formation models, with many having already assembled a large mass in stars approximately 12 billion years ago. However, masses of distant galaxies are uncertain, as they assume a distribution of stellar birth masses (the initial mass function (IMF)) similar to that in the Milky Way. Specifically, the contribution from low-mass stars, which make up the bulk of stellar mass, is not directly observed, but inferred based on an extrapolation of the Milky Way IMF. Here, we provide robust constraints on the low-mass IMF beyond the local Universe from full-spectrum models. Using ultra-deep spectra of nine massive quiescent galaxies at redshift $z$ $\approx0.7$ from the JWST Initial Mass Function of Early Red NIRSpec Objects program, extended to bluer wavelengths with deep Very Large Telescope Large Early Galaxy Astrophysics Census spectra, we find that the most massive galaxies have excess low-mass stars. Remarkably, our oldest galaxy (formation redshift $z_{\rm form} > 5$) has the most bottom-heavy IMF. This galaxy may be a descendant of JWST's 'impossibly early' galaxies, implying that the latter may have had similarly bottom-heavy IMFs increasing their masses by a factor of approximately $4\pm1$. Our findings may thus amplify the tension with galaxy formation models.

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$\sigma$ 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

Radiation magnetohydrodynamics simulations of Population III star formation during the Epoch of Reionization

Cosmological simulations find that pockets of star-forming gas could remain pristine up until the Epoch of Reionization (EoR) due to the inhomogeneous nature of metal mixing and enrichment in the early Universe. Such pristine clouds could have formed Population III stars, which could have distinct properties compared to their very high redshift ($z \geq 20$) counterparts. We investigate how Population III stars form and grow during the EoR, and whether the resulting mass distribution varies with environment or across cosmic time. We perform high-resolution ($7.5\,\rm{au}$) radiation-magnetohydrodynamics simulations of identical primordial clouds exposed to the CMB appropriate for $z=30$ and $z=6$, respectively, as part of the POPSICLE project. We also run a simulation at $z=6$ with a strong external Lyman-Werner (LW) background, to span across radiative environments which could host metal-free clumps during the EoR. In the limit of no external LW radiation, we find that while the evolution of the most massive star ($M_{\star} \approx 70\,\rm{M_{\odot}}$) is almost identical between $z=30$ and $z=6$, the latter exhibits less fragmentation, leading to a smaller cluster of stars with a higher median stellar mass. In the limit of high external LW radiation, we see vigorous accretion and high star formation efficiencies, leading to the formation of very massive ($M_{\star} > 100\,\rm{M_{\odot}}$) stars. Our results suggest that Population III IMF could vary with redshift simply due to the CMB, independent of the environment. We find that less massive and more compact Pop III star clusters could form during the EoR as compared to $z \geq 20$, with the formation of very massive and supermassive stars likely in strongly irradiated environments.

astro-ph.GA↗

arXiv2025

Chandra Large Project Observations of the Supernova Remnant N132D: Measuring the Expansion of the Forward Shock

We present results from the Chandra X-ray Observatory Large Project (878 ks in 28 observations) of the Large Magellanic Cloud supernova remnant N132D. We measure the expansion of the forward shock in the bright southern rim to be $0.\!^{\prime\prime}10 \pm 0.\!^{\prime\prime}02$ over the $\sim14.5$ yr baseline, which corresponds to a velocity of $1620\pm400~\mathrm{km\,s^{-1}}$ after accounting for several instrumental effects. We measure an expansion of $0.\!^{\prime\prime}23 \pm 0.\!^{\prime\prime}02$ and a shock velocity of $3840\pm260~\mathrm{km\,s^{-1}}$ for two features in an apparent blowout region in the northeast. The emission-measure-weighted average temperature inferred from X-ray spectral fits to regions in the southern rim is $0.95\pm0.17$ keV, consistent with the electron temperature implied by the shock velocity after accounting for Coulomb equilibration and adiabatic expansion. In contrast, the emission-measure-weighted average temperature for the northeast region is $0.77\pm0.04$ keV, which is significantly lower than the value inferred from the shock velocity. We fit 1-D evolutionary models for the shock in the southern rim and northeast region, using the measured radius and propagation velocity into a constant density and power-law profile circumstellar medium. We find good agreement with the age of $\sim2500$ years derived from optical expansion measurements for explosion energies of $1.5-3.0 \times 10^{51}\,\mathrm{erg}$, ejecta masses of $2-6 \,\mathrm{M_{\odot}}$ and ambient medium densities of $\sim0.33-0.66$ $\mathrm{amu~cm}^{-3}$ in the south and $\sim0.01-0.02$ $\mathrm{amu~cm}^{-3}$ in the northeast assuming a constant density medium. These results are consistent with previous studies that suggested the progenitor of N132D was an energetic supernova that exploded into a pre-existing cavity.

astro-ph.HE↗

arXiv2025

Cosmic Threads: Interlinking the Stellar Initial Mass Function from Star-Birth to Galaxies

The stellar initial mass function (sIMF) describes the distribution of stellar masses formed in a single star formation event in a molecular cloud clump. It is fundamental to astrophysics and cosmology, shaping our understanding of unresolved stellar populations, galactic chemical enrichment and habitable zones, and black hole growth. This White Paper reviews studies on the core mass function, stellar multiplicity, and dynamical processes affecting sIMF determinations, as well as the link between star-forming clumps and the galaxy-wide IMF (gIMF). The evidence gleaned from observed systems for the dependency of the sIMF on the metallicity and density of the clump is portrayed. We examine evidence from gravitational lensing, stellar and gas kinematics, and spectral diagnostics to assess environmental dependencies of the gIMF. Theoretical perspectives provide further insights into the sIMF's variability. Beyond summarizing current knowledge, this work aims to establish a shared framework and define strategies for studying a variable IMF in the era of near-infrared integral-field spectroscopy, 30m-class telescopes and major space-based observatories.

astro-ph.GA↗

arXiv2025

Does the HCN/CO ratio trace the star-forming fraction of gas? II. Variations in CO and HCN Emissivity

We model emissivities of the HCN and CO $J=1-0$ transitions using measured properties of clouds found in normal star forming galaxies and more extreme systems. These models are compared with observations of HCN and CO $J=1-0$ transitions. We combine these model emissivities with predictions of gravoturbulent models of star formation, explore the impact of excitation and optical depth on CO and HCN emission, and assess if observed HCN/CO ratios track the fraction of gravitationally-bound dense gas, $f_\mathrm{grav}$, in molecular clouds. Our modeled HCN/CO ratios and emissivities are consistent with measurements from observations. CO emission shows a range of optical depths across different environments, from optically thick in normal galaxies to moderately optically thin in extreme systems. HCN is only moderately optically thick, with significant subthermal excitation in both normal and extreme galaxies. We find an anticorrelation between HCN/CO and $f_\mathrm{grav}$ as predicted by gravoturbulent models of star formation. Instead this ratio tracks gas at moderate densities ($n>10^{3.5}\ \mathrm{cm}^{-3}$), which is below the standard dense gas threshold of $n>10^{4.5}\ \mathrm{cm}^{-3}$. Variations in CO emissivity depend strongly on optical depth, due to variations in the dynamics of the cloud gas. HCN emissivity depends more strongly on excitation, and thus does not directly track variations in CO emissivity. We conclude that a single line ratio, such as HCN/CO, will not consistently track the fraction of gravitationally-bound, star-forming gas if the critical density for star formation varies in molecular clouds. This work highlights important uncertainties that need to be considered when observationally applying an HCN conversion factor in order to estimate the dense (i.e. $n>10^{4.5}\ \mathrm{cm}^{-3}$) gas content in nearby galaxies.

astro-ph.GA↗

arXiv2025

Magnetic fields limit the mass of Population III stars even before the onset of protostellar radiation feedback

The masses of Population III stars are largely unconstrained since no simulations exist that take all relevant primordial star formation physics into account. We perform the first suite of radiation magnetohydrodynamics (RMHD) simulations of Population III star formation, with the POPSICLE project. Compared to control simulations that only include magnetic fields (MHD), protostellar ionizing and dissociating feedback, or neither, the RMHD simulation best resembles the MHD simulation during the earliest stages of collapse and star formation. In $5000\,\rm{yrs}$, the mass of the most massive star is $65\,\rm{M_{\odot}}$ in the RMHD simulation, compared to $120\,\rm{M_{\odot}}$ in simulations without magnetic fields. This difference arises because magnetic fields act against gravity, suppress mass transport, and reduce compressional heating. The maximum stellar mass of Population III stars is thus already limited by magnetic fields, even before accretion rates drop to allow significant protostellar radiative feedback. Following classical main sequence stellar evolution with MESA reveals that it is difficult to create Population III stars with masses larger than $600\,\rm{M_{\odot}}$ in typical dark matter minihaloes at $z \gtrsim 20$, with maximum stellar masses $\sim 100\,\rm{M_{\odot}}$ more likely due to expected negative feedback from both magnetic fields and stellar radiation. This work lays the first step in building a full physics-informed mass function of Population III stars.

astro-ph.GA↗

arXiv2024

A path towards constraining the evolution of the interstellar medium and outflows in the Milky Way using APOGEE

In recent years, the study of the Milky Way has significantly advanced due to extensive spectroscopic surveys of its stars, complemented by astroseismic and astrometric data. However, it remains disjoint from recent advancements in understanding the physics of the Galactic interstellar medium (ISM). This paper introduces a new model for the chemical evolution of the Milky Way that can be constrained on stellar data, because it combines a state-of-the-art ISM model with a Milky Way stellar disc model. Utilizing a dataset of red clump stars from APOGEE, known for their precise ages and metallicities, we concentrate on the last 6 billion years -- a period marked by Milky Way's secular evolution. We examine the oxygen abundance in the low-$α$ disc stars relative to their ages and birth radii, validating or constraining critical ISM parameters that remain largely unexplored in extragalactic observations. The models that successfully reproduce the radius -- metallicity distribution and the age -- metallicity distribution of stars without violating existing ISM observations indicate a need for modest differential oxygen enrichment in Galactic outflows, meaning that the oxygen abundance of outflows is higher than the local ISM abundance, irrespective of outflow mass loading. The models also suggest somewhat elevated ISM gas velocity dispersion levels over the past 6 billion years compared to galaxies of similar mass. The extra turbulence necessary could result from energy from gas accretion onto the Galaxy, supernovae clustering in the ISM, or increased star formation efficiency per freefall time. This work provides a novel approach to constraining the Galactic ISM and outflows, leveraging the detailed insights available from contemporary Milky Way surveys.

astro-ph.GA↗

arXiv2024

Population III star formation in the presence of turbulence, magnetic fields and ionizing radiation feedback

Turbulence, magnetic fields and radiation feedback are key components that shape the formation of stars, especially in the metal-free environments at high redshifts where Population III stars form. Yet no 3D numerical simulations exist that simultaneously take all of these into account. We present the first suite of radiation-magnetohydrodynamics (RMHD) simulations of Population III star formation using the adaptive mesh refinement (AMR) code FLASH as part of the POPSICLE project. We include both turbulent magnetic fields and ionizing radiation feedback coupled to primordial chemistry, and resolve the collapse of primordial clouds down to few au. We find that dynamically strong magnetic fields significantly slow down accretion onto protostars, while ionizing feedback, as expected, is largely unable to weaken gas accretion at early times. This is because the partially ionized H II region gets trapped near the star due to insufficient radiative outputs from the star. The maximum stellar mass in the HD and RHD simulations that only yield one star exceeds $100\,\rm{M_{\odot}}$ within the first $5000\,\rm{yr}$. However, in the corresponding MHD and RMHD runs, the maximum mass of Population III stars is only $60\,\rm{M_{\odot}}$. In other realizations where we observe widespread fragmentation leading to the formation of Population III star clusters, the maximum stellar mass is further reduced by a factor of few due to fragmentation-induced starvation. We thus show that magnetic fields are more important than ionizing feedback in regulating the mass of the star during the earliest stages of Population III star formation.

astro-ph.GA↗

arXiv2024

The MAGPI Survey: Evolution of radial trends in star formation activity across cosmic time

Using adaptive optics with the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey allows us to study the spatially resolved Universe at a crucial time of ~4 Gyr ago ($z$ ~ 0.3) when simulations predict the greatest diversity in evolutionary pathways for galaxies. We investigate the radial trends in the star formation (SF) activity and luminosity-weighted stellar ages as a function of offset from the star-forming main sequence (SFMS) for a total of 294 galaxies. Using both H$α$ emission and the 4000 Angstrom break (i.e., D4000) as star formation rate (SFR) tracers, we find overall flat radial profiles for galaxies lying on and above the SFMS, suggestive of physical processes that enhance/regulate SF throughout the entire galaxy disc. However, for galaxies lying below the SFMS, we find positive gradients in SF suggestive of inside-out quenching. Placing our results in context with results from other redshift regimes suggests an evolution in radial trends at $z$ ~ 0.3 for SF galaxies above the SFMS, from uniformly enhanced SF at $z$ ~ 1 and $z$ ~ 0.3 to centrally enhanced SF at $z$ ~ 0 (when averaged over a wide range of mass). We also capture higher local SFRs for galaxies below the SFMS compared to that of $z$ ~ 0, which can be explained by a larger population of quenched satellites in the local Universe and/or different treatments of limitations set by the D4000-sSFR relation.

astro-ph.GA↗

arXiv2024

The interplay between feedback, accretion, transport and winds in setting gas-phase metal distribution in galaxies

The recent decade has seen an exponential growth in spatially-resolved metallicity measurements in the interstellar medium (ISM) of galaxies. To first order, these measurements are characterised by the slope of the radial metallicity profile, known as the metallicity gradient. In this work, we model the relative role of star formation feedback, gas transport, cosmic gas accretion, and galactic winds in driving radial metallicity profiles and setting the mass-metallicity gradient relation (MZGR). We include a comprehensive treatment of these processes by including them as sources that supply mass, metals, and energy to marginally unstable galactic discs in pressure and energy balance. We show that both feedback and accretion that can drive turbulence and enhance metal-mixing via diffusion are crucial to reproduce the observed MZGR in local galaxies. Metal transport also contributes to setting metallicity profiles, but it is sensitive to the strength of radial gas flows in galaxies. While the mass loading of galactic winds is important to reproduce the mass metallicity relation (MZR), we find that metal mass loading is more important to reproducing the MZGR. Specifically, our model predicts preferential metal enrichment of galactic winds in low-mass galaxies. This conclusion is robust against our adopted scaling of the wind mass-loading factor, uncertainties in measured wind metallicities, and systematics due to metallicity calibrations. Overall, we find that at $z \sim 0$, galactic winds and metal transport are more important in setting metallicity gradients in low-mass galaxies whereas star formation feedback and gas accretion dominate setting metallicity gradients in massive galaxies.

astro-ph.GA↗

arXiv2023

The MAGPI Survey: Effects of Spiral Arms on Different Tracers of the Interstellar Medium and Stellar Populations at z~0.3

Spiral structures are important drivers of the secular evolution of disc galaxies, however, the origin of spiral arms and their effects on the development of galaxies remain mysterious. In this work, we present two three-armed spiral galaxies at z~0.3 in the Middle Age Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Taking advantage of the high spatial resolution (~0.6'') of the Multi-Unit Spectroscopic Unit (MUSE), we investigate the two-dimensional distributions of different spectral parameters: Halpha, gas-phase metallicity, and D4000. We notice significant offsets in Halpha (~0.2 dex) as well as gas-phase metallicities (~0.05 dex) among the spiral arms, downstream and upstream of MAGPI1202197197 (SG1202). This observational signature suggests the spiral structure in SG1202 is consistent with arising from density wave theory. No azimuthal variation in Halpha or gas-phase metallicities is observed in MAGPI1204198199 (SG1204), which can be attributed to the tighter spiral arms in SG1204 than SG1202, coming with stronger mixing effects in the disc. The absence of azimuthal D4000 variation in both galaxies suggests the stars at different ages are well-mixed between the spiral arms and distributed around the disc regions. The different azimuthal distributions in Halpha and D4000 highlight the importance of time scales traced by various spectral parameters when studying 2D distributions in spiral galaxies. This work demonstrates the feasibility of constraining spiral structures by tracing interstellar medium (ISM) and stellar population at z~0.3, with a plan to expand the study to the full MAGPI survey.

astro-ph.GA↗

arXiv2023

The MAGPI Survey: Impact of environment on the total internal mass distribution of galaxies in the last 5 Gyr

We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift $z \sim 0.3$, corresponding to a lookback time of $3-4$ Gyr. The internal mass distribution for each galaxy is parameterised by the combined mass density slope $γ$ (baryons $+$ dark matter), which is the logarithmic change of density with radius. We use a MAGPI sample of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range $0.29 <z < 0.55$, corresponding to a lookback time of $\sim 5$ Gyr. We find a median density slope of $γ= -2.22 \pm 0.05$ for the MAGPI sample, which is significantly steeper than the Frontier Fields median slope ($γ= -2.01 \pm 0.04$), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in Atlas3D at $z \sim 0$, because the sample probes a similar environmental range as MAGPI. The Atlas3D median total slope is $γ= -2.25 \pm 0.02$, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3-4 Gyr. These results are in agreement with the predictions of cosmological simulations.

astro-ph.GA↗