arXiv subjects

S. Thater

Publications and source records attributed to S. Thater.

8 recordsLinked to original sources

arXiv2026

The MAGPI Survey: Emission Line Products Data Release and the Role of Spectroscopic Aperture Covering Fraction on the Balmer Decrement-Stellar Mass Relation

The Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey is a Large Program on the European Southern Observatory Very Large Telescope using the MUSE instrument. This paper presents the data release for the MAGPI emission line products and includes emission line maps for 836 galaxies at $0.05\leq z_\mathrm{spec}\leq 0.424$ ($\mathrm{H}\alpha$-window) and aperture-based emission line measurements for 2,607 galaxies at $0.05\leq z_\mathrm{spec}\leq 1.50$ (upper bound is [OII] cut-off), both based on the GIST software, for all 56 MAGPI fields. We use these data to examine dust attenuation, which represents a major source of uncertainty in the derived properties of galaxies that are critical to constrain models of galaxy evolution. We examine the role that the spectroscopic aperture covering fraction ($f_c$) has on the relationship between the Balmer decrement ($\mathrm{BD}=F(\mathrm{H}\alpha)/F(\mathrm{H}\beta)$; a common proxy for dust attenuation) and the total stellar mass ($M_\star$). Several studies have suggested that the BD-$M_\star$ relation may be redshift invariant; however, the compared surveys often have different $f_c$ due to their differing fibre or slit sizes that can cause systematic offsets. Our results indicate that $f_c$ has a significant impact on this relationship, due to galaxies having negative BD radial gradients, which are more negative for more massive galaxies at $z\lesssim0.4$. Comparing spectroscopic surveys with $\left \gtrsim 0.5$, we find that the BD-$M_\star$ relation shows a preference for redshift evolution and is roughly consistent with the behaviour of UV stellar continuum attenuation redshift evolution ($A_\mathrm{FUV}$-$z$), with the average dust attenuation in galaxies peaking at $z\sim1.2$ and decreasing at lower and higher redshifts.

astro-ph.GA↗

arXiv2026

A spectroscopic map of the Galactic centre: Integrated light and dynamical modelling

The centre of the Milky Way is occupied by a nuclear star cluster that contains the supermassive black hole Sgr A*. The cluster is embedded in the larger surrounding nuclear stellar disc. These three components dominate the mass budget of the Galactic centre at different radial scales. The mass distribution of the Galactic centre has been studied extensively using observations of individual bright stars and various dynamical modelling approaches. The situation differs for external galaxies, where observations are often limited to the integrated line-of-sight kinematics. For such systems, triaxial orbit-based dynamical modelling has become a standard method of deriving mass distributions and stellar orbit distributions. We aim to apply and test this method on the Galactic centre. We extracted stellar line-of-sight kinematic maps of the inner ~3 pc x 66 pc region of the Galactic centre. We used the DYNAMITE code, which calculates an orbit library in a given gravitational potential and computes model kinematic maps. These maps were then compared to the observed kinematic maps, and the gravitational potential and orbit distribution of the Galactic centre were constrained. We recover the correct mass of Sgr A*, and our stellar mass distributions are in agreement with the literature, albeit with larger uncertainties. The stellar structures are at most mildly triaxial and close to oblate. The stellar orbit distribution in the inner region is dominated by dynamically warm and hot orbits. At larger scales, dynamically cold -- highly rotating -- orbits have the largest weights. The dominance of hot and warm orbits is a consequence of short dynamical timescales in the inner Galactic centre, causing dynamical heating. The presence of cold orbits at large radii may be explained by the longer heating timescales in this region, and by the stars in the outer nuclear stellar disc being younger.[abridged]

astro-ph.GA↗

arXiv2026

MAUVE: Cold neutral gas in the outflow of NGC 4383 and evidence for a fountain flow

We present a multiphase study of the star-formation-driven outflow in the Virgo galaxy NGC 4383, combining ALMA CO(2-1) data with deep MeerKAT HI imaging and MUSE spectroscopy obtained as part of the Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) program. Our previous work revealed a spectacular ionised outflow, but the effect of the outflow on the cold phase remained unclear. Our analysis shows that potentially outflowing molecular gas is detected only within the inner 1 kpc above the disc, where CO clouds exhibit disturbed kinematics and spatial correspondence with the ionisation cone. At larger heights, the CO surface brightness rapidly drops, indicating that the molecular phase contributes little to the mass of outflowing gas. In contrast, the HI distribution shows plumes a few kiloparsecs above the disc that are aligned with the ionised cone, and complex kinematics suggestive of parts of the atomic phase being entrained in the outflow. However, the extended and warped HI disc associated with NGC 4383 complicates the unambiguous identification of outflowing atomic gas and, most importantly, the quantification of outflowing mass and loading factor. Independent support for a cold component in the outflow comes from dust extinction features associated with the outflow and coincident with HI plumes. Despite significant uncertainties in the estimate of the mass of cold gas associated with the outflow, these results suggest that the atomic phase likely dominates the cold outflow above 1 kpc. The observed cold gas velocities remain below the velocities of the ionised phase, suggesting that NGC 4383 does not host a large-scale escaping wind but more likely a galactic fountain, in which feedback redistributes material within the halo and regulates ongoing and future star formation.

astro-ph.GA↗

arXiv2025

Connecting galaxies with their haloes -- from parsec to Mpc scales

Galaxy evolution is driven by processes occurring across a wide range of scales, from star formation within giant molecular clouds (parsec scales) to outflows and secular evolution across entire galaxies (kpc scales), and the interplay between galaxies, their dark matter haloes, and large-scale structures (Mpc scales). Connecting the distribution of baryonic matter and energy across these scales will remain one of the key challenges for both theoretical and observational astrophysics in the coming decade. A major development towards meeting this challenge has been the growing ability to obtain highly spatially resolved (parsec-scale) integral-field spectroscopic observations (e.g. with VLT/MUSE), as well as to probe the extremely low-surface brightness outskirts of galaxies at large radii and high vertical scale heights. To combine the two regimes, we need a paradigm shift in the way we do spectroscopy on galaxies, especially considering the ongoing and future photometric surveys. The next decade will also bring a revolution in extensive photometric surveys of large areas of the sky, uncovering low surface brightness features around nearby galaxies. However, to fully understand the processes that connect galaxies to their haloes, shape low surface brightness features, and drive secular evolution, spatially resolved spectroscopy will be essential. Here, we outline the need for wide-field spectroscopic observations of statistically significant samples of nearby galaxies and highlight the key questions that can only be addressed with such data

astro-ph.GA↗

arXiv2024

The MAGPI Survey: Insights into the Lyman-alpha line widths and the size of ionized bubbles at the edge of cosmic reionization

We present spectroscopic properties of 22 Lyman-alpha emitters(LAEs) at z=5.5-6.6 with Lyman-alpha(Lya) luminosity log($L_{Lya}$[$ergs^{-1}$])=42.4-43.5, obtained using VLT/MUSE as part of the Middle Ages Galaxy Properties with Integral Field Spectroscopy(MAGPI) survey. Additionally, we incorporate broad-band photometric data from the Subaru Hyper Suprime-Cam(HSC) for 17 LAEs in our sample. The HSC-y band magnitudes show that our LAEs are UV-bright, with rest-frame absolute UV magnitudes -19.7 < $M_{UV}$ < -23.3. We find that the Lya line width increases with luminosity, and this trend becomes more prominent at z > 6 where Lya lines become significantly broadened (> 260 $kms^{-1}$) at luminosities log($L_{Lya}$[$ergs^{-1}$]) > 43. This broadening is consistent with previous studies, suggesting that these sources are located inside larger ionized bubbles. We observe a slightly elevated ionizing photon production efficiency estimated for LAEs at z > 6, indicating that younger galaxies could be producing more ionizing photons per UV luminosity. A tentative anti-correlation between ionizing photon production efficiency and Lya rest-frame equivalent width is noticed, which could indicate a time delay between production and escape of ionizing photon primarily due to supernovae activity. Furthermore, we find a positive correlation between bubble radius and Lya line width, which again suggests that large ionized bubbles are created around these LAEs, allowing them to self-shield from the scattering effects of the intergalactic medium (IGM). We also detect two closely separated LAEs at z=6.046 (projected spatial separation is 15.92 kpc). The size of their respective bubbles suggests that they likely sit inside a common large ionized region. Such a closely-separated LAE pair increases the size of ionized bubble, potentially allowing a boosted transmission of Lya through neutral IGM. (Abridged)

astro-ph.GA↗

arXiv2024

The MAGPI Survey: Evidence Against the Bulge-Halo Conspiracy

Studies of the internal mass structure of galaxies have observed a `conspiracy' between the dark matter and stellar components, with total (stars $+$ dark) density profiles showing remarkable regularity and low intrinsic scatter across various samples of galaxies at different redshifts. Such homogeneity suggests the dark and stellar components must somehow compensate for each other in order to produce such regular mass structures. We test the conspiracy using a sample of 22 galaxies from the `Middle Ages Galaxy Properties with Integral field spectroscopy' (MAGPI) Survey that targets massive galaxies at $ z \sim 0.3$. We use resolved, 2D stellar kinematics with the Schwarzschild orbit-based modelling technique to recover intrinsic mass structures, shapes, and dark matter fractions. This work is the first implementation of the Schwarzschild modelling method on a sample of galaxies at a cosmologically significant redshift. We find that the variability of structure for combined mass (baryonic and dark) density profiles is greater than that of the stellar components alone. Furthermore, we find no significant correlation between enclosed dark matter fractions at the half-light radius and the stellar mass density structure. Rather, the total density profile slope, $\gamma_{\mathrm{tot}}$, strongly correlates with the dark matter fraction within the half-light radius, as $\gamma_{\mathrm{tot}} = (1.3 \pm 0.2) f_{\mathrm{DM}} - (2.44 \pm 0.04)$. Our results refute the bulge-halo conspiracy and suggest that stochastic processes dominate in the assembly of structure for massive galaxies.

astro-ph.GA↗

arXiv2024

The MAGPI survey: The interdependence of the mass, star formation rate, and metallicity in galaxies at z~0.3

Star formation rates (SFRs), gas-phase metallicities, and stellar masses are crucial for studying galaxy evolution. The different relations resulting from these properties give insights into the complex interplay of gas inside galaxies and their evolutionary trajectory and current characteristics. We aim to characterize these relations at $z\sim 0.3$, corresponding to a 3-4 Gyr lookback time. We utilized optical integral field spectroscopy of 65 emission-line galaxies from the MAGPI survey at a redshift of $0.28<z<0.35$ and spanning a total stellar mass range of $8.2<\log(M_{*}/M_{\odot}) < 11.4$. We derived the resolved star formation main sequence (rSFMS), resolved mass metallicity relation (rMZR), and resolved fundamental metallicity relation (rFMR) at $z\sim 0.3$. We find a relatively shallow rSFMS slope of $\sim 0.425 \pm 0.014$ compared to the expected slope at this redshift for an ordinary least square (OLS) fitting routine. For an orthogonal distance regression (ODR) routine, a much steeper slope of $\sim 1.162 \pm 0.022$ is measured. We confirm the existence of an rMZR at $z\sim 0.3$ with an average metallicity located $\sim 0.03$ dex above the local Universe's metallicity. Via partial correlation coefficients, evidence is found that the local metallicity is predominantly determined by the stellar mass surface density and has a weak secondary (inverse) dependence on the SFR surface density $\Sigma_{SFR}$. Additionally, a significant dependence of the local metallicity on the total stellar mass $M_{*}$ is found. Furthermore, we find that the stellar mass surface density $\Sigma_{*}$ and $M_{*}$ have a significant influence in determining the strength with which $\Sigma_{SFR}$ correlates with the local metallicity. We observe that at lower stellar masses, there is a tighter correlation between $\Sigma_{SFR}$ and the gas-phase metallicity, resulting in a more pronounced rFMR.

astro-ph.GA↗

arXiv2023

The MAGPI Survey: Drivers of kinematic asymmetries in the ionised gas of $z\sim0.3$ star-forming galaxies

Galaxy gas kinematics are sensitive to the physical processes that contribute to a galaxy's evolution. It is expected that external processes will cause more significant kinematic disturbances in the outer regions, while internal processes will cause more disturbances for the inner regions. Using a subsample of 47 galaxies ($0.27<z<0.36$) from the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey, we conduct a study into the source of kinematic disturbances by measuring the asymmetry present in the ionised gas line-of-sight velocity maps at the $0.5R_e$ (inner regions) and $1.5R_e$ (outer regions) elliptical annuli. By comparing the inner and outer kinematic asymmetries, we aim to better understand what physical processes are driving the asymmetries in galaxies. We find the local environment plays a role in kinematic disturbance, in agreement with other integral field spectroscopy studies of the local universe, with most asymmetric systems being in close proximity to a more massive neighbour. We do not find evidence suggesting that hosting an Active Galactic Nucleus (AGN) contributes to asymmetry within the inner regions, with some caveats due to emission line modelling. In contrast to previous studies, we do not find evidence that processes leading to asymmetry also enhance star formation in MAGPI galaxies. Finally, we find a weak anti-correlation between stellar mass and asymmetry (ie. high stellar mass galaxies are less asymmetric). We conclude by discussing possible sources driving the asymmetry in the ionised gas, such as disturbances being present in the colder gas phase (either molecular or atomic) prior to the gas being ionised, and non-axisymmetric features (e.g., a bar) being present in the galactic disk. Our results highlight the complex interplay between ionised gas kinematic disturbances and physical processes involved in galaxy evolution.

astro-ph.GA↗