arXiv subjects

R. -S. Remus

Publications and source records attributed to R. -S. Remus.

6 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

What's Missing in AGN Feedback? Lessons learnt from Magneticum, IllustrisTNG and Simba

Accurately balancing gas reservoirs, star formation, and feedback across cosmic time remains a central challenge for galaxy formation models in modern hydrodynamical simulations. While different feedback prescriptions reproduce selected local galaxy properties with varying success, the most pronounced discrepancies emerge in predictions for the hot gas content of dark matter halos. We examine three state-of-the-art cosmological simulations: Magneticum, IllustrisTNG, and SIMBA, which struggle to simultaneously reproduce observed galaxy and halo gas properties in the local Universe. We confront their predictions with spatially resolved galaxy data from MaNGA and recent constraints on the hot gas mass fraction-halo mass (fgas-Mh) relation from eROSITA and Sunyaev-Zel'dovich (SZ) measurements. Reproducing the observed fgas-Mh relation requires strong active galactic nucleus (AGN) feedback. However, such feedback often leads to excessive quenching in simulated galaxy populations. Magneticum and SIMBA match the observed gas fraction relation but predict an overabundance of quenched galaxies. In contrast, IllustrisTNG implements weaker AGN feedback, yielding more realistic star-forming fractions but systematically overpredicting hot gas masses in massive groups and poor clusters. Overall, these tensions indicate current feedback models remain incomplete, not only in the total energy injected but also in the timing, location, and coupling of this energy to the surrounding gas. Our results therefore highlight the need to revisit subgrid feedback prescriptions and develop more self-consistent models capable of simultaneously regulating galaxy growth and the thermodynamic properties of halo gas. Motivated by this discrepancy, a companion study will explore whether the feedback strengths required to match halo gas constraints inevitably lead to overquenching and distorted galaxy demographics.

astro-ph.GA↗

arXiv2024

SLOW IV: Not all that is Close will Merge in the End. Superclusters and their Lagrangian collapse regions

Superclusters are the most massive structures in the universe. To what degree they are actually bound against an accelerating expansion of the background is of significant cosmological and astrophysical interest. In this study, we introduce a cross matched set of superclusters from the SLOW constrained simulations of the local (z<0.05) universe. Identifying the superclusters provides estimates on the efficacy of the constraints in reproducing the local large-scale structure accurately. The simulated counterparts can help identifying possible future observational targets containing interesting features such as bridges between pre-merging and merging galaxy clusters and collapsing filaments and provide comparisons for current observations. By determining the collapse volumes for the superclusters we further elucidate the dynamics of cluster-cluster interactions in those regions. Using catalogs of local superclusters and the most massive simulated clusters, we search for counterparts of supercluster members of six regions. We evaluate the significance of these detections by comparing their geometries to supercluster regions in random simulations. We then run an N-body version of the simulation into the far future and determine which of the member clusters are gravitationally bound to the host superclusters. Furthermore we compute masses and density contrasts for the collapse regions. We demonstrate the SLOW simulation of the local universe to accurately reproduce local supercluster regions in mass of their members and three-dimensional geometrical arrangement. We furthermore find the bound regions of the local superclusters consistent in size and density contrast with previous theoretical studies. This will allow to connect future numerical zoom-in studies of the clusters to the large scale environments and specifically the supercluster environments these local galaxy clusters evolve in.

astro-ph.CO↗

arXiv2021

The MAGPI Survey -- science goals, design, observing strategy, early results and theoretical framework

We present an overview of the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey, a Large Program on ESO/VLT. MAGPI is designed to study the physical drivers of galaxy transformation at a lookback time of 3-4 Gyr, during which the dynamical, morphological, and chemical properties of galaxies are predicted to evolve significantly. The survey uses new medium-deep adaptive optics aided MUSE observations of fields selected from the GAMA survey, providing a wealth of publicly available ancillary multi-wavelength data. With these data, MAGPI will map the kinematic and chemical properties of stars and ionised gas for a sample of 60 massive (> 7 x 10^10 M_Sun) central galaxies at 0.25 < z <0.35 in a representative range of environments (isolated, groups and clusters). The spatial resolution delivered by MUSE with Ground Layer Adaptive Optics (GLAO, 0.6-0.8 arcsec FWHM) will facilitate a direct comparison with Integral Field Spectroscopy surveys of the nearby Universe, such as SAMI and MaNGA, and at higher redshifts using adaptive optics, e.g. SINS. In addition to the primary (central) galaxy sample, MAGPI will deliver resolved and unresolved spectra for as many as 150 satellite galaxies at 0.25 < z <0.35, as well as hundreds of emission-line sources at z < 6. This paper outlines the science goals, survey design, and observing strategy of MAGPI. We also present a first look at the MAGPI data, and the theoretical framework to which MAGPI data will be compared using the current generation of cosmological hydrodynamical simulations including EAGLE, Magneticum, HORIZON-AGN, and Illustris-TNG. Our results show that cosmological hydrodynamical simulations make discrepant predictions in the spatially resolved properties of galaxies at z ~ 0.3. MAGPI observations will place new constraints and allow for tangible improvements in galaxy formation theory.

astro-ph.GA↗

arXiv2015

An improved SPH scheme for cosmological simulations

We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations of galaxies and the large-scale structure. In particular, we combine, implement, modify and test a vast majority of SPH improvement techniques in the latest instalment of the GADGET code. We use the Wendland kernel functions, a particle wake-up time-step limiting mechanism and a time-dependent scheme for artificial viscosity, which includes a high-order gradient computation and shear flow limiter. Additionally, we include a novel prescription for time-dependent artificial conduction, which corrects for gravitationally induced pressure gradients and largely improves the SPH performance in capturing the development of gas-dynamical instabilities. We extensively test our new implementation in a wide range of hydrodynamical standard tests including weak and strong shocks as well as shear flows, turbulent spectra, gas mixing, hydrostatic equilibria and self-gravitating gas clouds. We jointly employ all modifications; however, when necessary we study the performance of individual code modules. We approximate hydrodynamical states more accurately and with significantly less noise than standard SPH. Furthermore, the new implementation promotes the mixing of entropy between different fluid phases, also within cosmological simulations. Finally, we study the performance of the hydrodynamical solver in the context of radiative galaxy formation and non-radiative galaxy cluster formation. We find galactic disks to be colder, thinner and more extended and our results on galaxy clusters show entropy cores instead of steadily declining entropy profiles. In summary, we demonstrate that our improved SPH implementation overcomes most of the undesirable limitations of standard SPH, thus becoming the core of an efficient code for large cosmological simulations.

astro-ph.CO↗

arXiv2015

Connecting Angular Momentum and Galactic Dynamics: The complex Interplay between Spin, Mass, and Morphology

The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use the Magneticum simulations. We successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40 percent smaller than the specific angular momentum of the total DM halo and shows a significant scatter.

astro-ph.GA↗