arXiv subjects

Facundo A. Gómez

Publications and source records attributed to Facundo A. Gómez.

At least 19 recordsLinked to original sources

arXiv2026

The progenitor galaxies of the intracluster light

Intracluster Light (ICL) is a diffuse stellar component of galaxy groups and clusters, bound to the structure's potential rather than to individual galaxies and primarily formed through the stripping and mergers of intermediate-mass galaxies. Its formation and evolution is strongly linked to the central galaxies of groups and clusters, typically the Brightest Cluster Galaxies (BCGs) in clusters. To determine the properties of the progenitor galaxies of the ICL of clusters and groups at redshift z = 0 and compare them with the progenitors of their BCGs. We select 127 clusters and groups in the hydrodynamic Illustris-TNG100 simulation above a mass of 10^{13}~$M_{\odot}$. We divide the ICL from the BCG by applying a surface brightness cut at the Holmberg radius of 26.5 mag/arcsec^{-2}, where star particles within this radius are defined as attached to the BCG, and outside, the ICL. We then determine the masses and contributions of progenitor galaxies of the ICL and BCG. We find that the number of ICL progenitors increases with structure mass, and that the ICL has more progenitors than the BCG. The ICL has a larger percentage of material from low-mass galaxies. Quenched galaxies contributed a large fraction of the ICL, and this fraction increases with galaxy mass. The mean mass radial gradient of ex-situ material in structures for the ICL and the BCG+ICL is generally negative and increases with structure mass, indicating that material from more massive progenitors is found towards the centres of clusters. The mean mass radial gradient is significantly impacted by structure formation history. ICL progenitor properties are impacted by structure history and are therefore highly individual to each system. At a given structure mass, there is diversity in the properties of the progenitors that formed the ICL. Although the BCG and the ICL co-evolve, the BCG has fewer, more massive progenitors.

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arXiv2026

The extreme Disturbed Galaxy Cluster Sample (eDGeS): Spectroscopy and Dynamical Analysis of the eROSITA-Selected Merging Galaxy Cluster Candidate 1eRASS J025859.4-193727

Addressing open questions such as the effect of galaxy cluster mergers on the evolution of galaxies and the self-interaction cross-section of dark matter requires the construction of a large, diverse sample of disturbed galaxy clusters. One contribution to such a sample is the extreme Disturbed Galaxy Cluster Sample (eDGeS), an ongoing spectroscopic study of massive disturbed and merging galaxy clusters selected from complementary surveys. Here, we present our first results from the eROSITA-selected subsample (eDGeS-eROSITA): a dynamical state analysis for the merging cluster candidate 1eRASS J025859.4-193727. We present the first spectroscopic redshift measurements for 76 galaxies in the direction of the cluster, confirming 51 as cluster members. The cluster displays a line-of-sight velocity dispersion of $σ_{\rm{cl}}=808^{+59}_{-66}~\rm{km~s^{-1}}$ and a dynamical mass of $M_{200}=4.47^{+0.94}_{-0.93} \times 10^{14}~M_{\rm{Sun}}$. While the cluster shows no evidence for substructure along the line of sight, the projected distribution of member galaxies reveals three subclusters, only one of which appears associated with the cluster's X-ray contours. Phase-space analysis reveals a large fraction of recently infallen member galaxies. Together, this evidence suggests a cluster merger along the plane of the sky. Assuming that the two most massive subclusters are on outgoing (incoming) trajectories after their first pericentric passage, a two-body Monte Carlo model predicts that the two subclusters collided $0.50^{+0.20}_{-0.22}~\rm{Gyr}$ ($1.24^{+0.96}_{-0.38}~\rm{Gyr}$) ago.

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arXiv2026

X-ray emission maps and scaling relations in IllustrisTNG and MillenniumTNG: Differences between cluster and group regimes

X-ray observations are a primary probe of the intracluster medium, widely used to infer galaxy cluster masses and scaling relations. We present and validate a pipeline to generate X-ray emission maps of galaxy groups and clusters from large cosmological simulations, and use it to study the origin of deviations from self-similarity across the group-to-cluster transition. We apply this pipeline to the Illustris-TNG300 and MillenniumTNG simulations, constructing \mbox{X-ray} emission maps and spectra based on APEC cooling functions. For simulations that do not explicitly track individual chemical abundances, we introduce a metallicity-based prescription that accurately reproduces the full spectral emission. We derive the $L_{\mathrm{X}}$--$M_{500}$, $M_{\mathrm{gas}}$--$M_{500}$, and $T$--$M_{500}$ scaling relations over $10^{12.5} \leq M_{500} \leq 10^{15.5}\,\mathrm{M}_\odot$, compare them with observational data, and quantify the hydrostatic equilibrium and spectroscopic temperature biases through synthetic X-ray analyses. The simulated scaling relations are in good overall agreement with observations and are best described by broken power laws with a pivot at $M_{500}=10^{13.67}\,\mathrm{M}_\odot$. At high masses, the slopes are close to self-similar expectations; at lower masses the relations steepen significantly, reflecting the growing importance of AGN feedback. X-ray hydrostatic masses are systematically underestimated by $15\%$, independently of cluster mass. When spectroscopic effects are included, the bias becomes mass-dependent, ranging from $15\%$ at low masses to $21\%$ at high masses. The recovered X-ray luminosity, measured in the $0.15$--$1\,R_{500}$ aperture, is also mass-dependent: high-mass clusters are underestimated by $18\%$, while low-mass systems show discrepancies of up to $33\%$, driven by single-temperature spectral modelling of the gas outside the core.

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arXiv2026

Characterizing the Formation and Evolution of S0-galaxies (CaFES-0): Their formation pathways around Galaxy Clusters

The formation pathways of lenticular galaxies (S0s), which lie morphologically between elliptical and spiral galaxies, remain a topic of active research. Environmental effects, merging histories, and pre-processing mechanisms are often proposed as key factors influencing their transformation. However, the relative importance of these processes remains unclear, particularly when compared with other galaxy types. We use the Hydrangea cosmological zoom-in simulation suite to analyse the environmental histories of S0 galaxies, defined here as central and satellite quenched disk galaxies. We find that the vast majority (>85\%) of our sample of S0s are satellites in massive haloes (log$_{10}$M$_{200}/$M$_\odot$ > 13), while only $\sim10\%$ are centrals in low-mass haloes. Satellite S0s exhibit a highly quiescent merging history, with $\sim60\%$ experiencing no significant mergers since $z=2$. Centrals show more varied merging histories, although our results may be affected by limited sample size. Contrary to expectations, no clear trends in merger ratios with morphology are observed. However, mergers involving lenticular and spiral galaxies tend to occur in low-density environments and are likely gas-rich, enabling disk reformation. Pre-processing effects in groups are critical, influencing both quenching and morphological transformation.} Our results strongly suggest that S0 galaxies predominantly form from faded/stripped spirals in clusters, with a minority forming via mergers in smaller haloes. These results are in agreement with previous observations of lenticular galaxies around galaxy clusters.

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arXiv2026

Something green beneath the surface: The dynamical nature of Fossil Structures in IllustrisTNG-100

Fossil structures (FS) have traditionally been considered dynamically relaxed end-products of group evolution, characterized by a large magnitude gap ($Δm_{1,2} \geq 2$). However, recent observations and simulations suggest this picture is incomplete. We investigate whether FS are dynamically relaxed systems and how their galaxy populations differ from non-fossil systems (non-FS), focusing on system dynamics and evolution of the galaxies inside them. Using \textsc{IllustrisTNG-100}, we select 182 structures ($M_{200} > 10^{13}\,M_{\odot}$) at $z = 0$, classifying them as FS/non-FS based on $Δm_{1,2}$ in the $r$-band. We track $Δm_{1,2}$ evolution over 9\,Gyr and analyze: (1) the emergence of $Δm_{1,2}$, (2) the fraction of quenched galaxies (sSFR $< 10^{-11}$\,yr$^{-1}$), (3) the distribution of galaxies in color--stellar mass space, and (4) the gas--BSG centroid shift as a dynamical proxy. The magnitude gap in FS is primarily driven by the absence of massive recent accretion: FS exhibit significantly lower BSG-to-satellite stellar mass ratios ($μ^{\rm{FS}}{\star}$=0.17 vs. $μ^{\rm{NFS}}{\star}$=0.39) for the most massive satellite accreted within the last 6\,Gyr. FS also host a more prominent red sequence and marginally higher quenched fractions than non-FS. Our findings indicate that while the magnitude gap effectively identifies systems that have ceased major mergers in the last 3-6 Gyr, it is a poor proxy for their current global dynamical state. Both FS and non-FS populations exhibit intermediate gas-BSG offsets ($D_{BSG-CM} \approx 0.15 R/R_{200}$), failing to reach full relaxation. This decoupling suggests that the magnitude gap traces the assembly history of massive components rather than the overall stability of the intra cluster medium.

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arXiv2026

Age and metallicity of low-mass galaxies: from their centres to their stellar halos

We aim to analyse the metallicity and the ages of the stellar halos of low-mass galaxies to better understand their formation history. We use 17 simulated low-mass galaxies from the Auriga Project ($\sim 3 \times 10^8 \, M_\odot \leq M_* \lesssim 2 \times 10^{10} \, M_\odot$). We study the metallicity and the ages of these galaxies and their stellar halos, as well as the relation between these two properties. We find that all galaxies have negative radial [Fe/H] gradients, and that the centres of less massive dwarfs are generally more metal poor than those of more massive dwarfs. We find no correlation between the metallicity gradients in dex/R$_h$ and intrinsic galaxy properties, such as stellar mass or accreted stellar mass, suggesting that these gradients are not a simple byproduct of galaxy evolution in the low-mass regime. We also find that the dispersion in the mass-metallicity relation found in the stellar halos of low-mass galaxies can be explained with the infall time of their most dominant satellite: at a fixed accreted stellar halo mass, dwarf galaxies that accreted this satellite at later times have more metal-rich accreted stellar halos. Regarding the ages of the analysed galaxies, we find a prominent U shape in the radial mean age profiles of $\sim 65\%$ of them, which is mainly driven by the in situ stellar material. This presence of a U shape in the age profiles is due to the combination of the cessation of recent star formation at large radial distances and the merger events these galaxies undergo, which redistribute the stellar material to their outer regions. When focusing on the ages of the stellar halos, we find that more massive ones are older than less massive ones. Our results show a wide variety in ages and metallicities of low-mass galaxies and their stellar halos, reflecting the complex and non-uniform evolutionary pathways these systems can follow.

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arXiv2026

Coupling between stellar and HI lopsidedness in Milky Way-type galaxies from the Auriga Superstars cosmological simulations

Lopsidedness is common in disk galaxies, yet its origin and evolution remain unclear. Previous studies typically examined stellar and gas asymmetries separately, but a combined analysis offers a stronger probe of the mechanisms driving lopsidedness, recent galaxy evolution, and environment. We analyze the density and kinematics of stellar and atomic hydrogen (HI) components in nine Milky Way type galaxies from the Auriga Superstars cosmological zoom-in simulations. The high stellar mass resolution improves the visibility of disk features while reducing noise, enabling a detailed study of dynamical processes in a cosmological context. Morphological and kinematical lopsidedness are quantified using the first Fourier mode (m=1) of the face-on mass distribution and radial velocity maps, measured consistently for stars and gas between 0.5 and 1 stellar optical radius. At z=0, morphological lopsidedness in old stars (>0.5Gyr) strongly correlates with HI, tracing distortions in the global gravitational potential. In contrast, young stars (<0.5Gyr) trace asymmetric star formation along spiral arms. Stellar morphological and kinematical lopsidedness are strongly correlated, whereas HI shows a weaker correlation, with kinematic asymmetries dominating. We also find an anti-correlation between stellar lopsidedness and bar strength. Strongly barred galaxies tend to host more symmetric disks and higher central stellar mass densities. Tracing lopsidedness evolution over time, tidal interactions with massive satellites (mass ratio >1:50) induce coherent lopsidedness in both stars and HI. In contrast, smooth gas accretion mainly affects HI and young stars, leaving the total stellar component largely symmetric. Overall, these results demonstrate that lopsidedness is a powerful diagnostic of internal disk evolution, gas accretion, and environmental interactions across cosmic time.

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arXiv2026

Coevolution of Intracluster Light and Brightest Cluster Galaxies

Context. Intracluster Light (ICL) is a faint stellar component of galaxy groups and clusters bound to the cluster potential, and making up a significant fraction of the cluster mass. ICL formation and evolution is strongly linked to the Brightest Cluster Galaxies of clusters. Aims. To compare the properties and progenitor galaxies of the Intracluster Light (ICL) and Brightest Cluster Galaxies (BCGs) of clusters and groups at redshift z = 0, and determine how they coevolve. Methods. We select 127 clusters and groups in the hydrodynamic Illustris-TNG100 simulation above a mass of $10^{13} M_\odot$. We divide the ICL from the BCG by applying a surface brightness cut at the Holmberg radius of 26.5 mag/arcsec$^{-2}$, where star particles within this radius are defined as being attached to the BCG, and outside, the ICL. We then study the properties and formation history of the ICL and BCG. Results. We find the ICL is generally composed of material from stripped or merged intermediate mass galaxies, with a smaller in-situ component, while the BCG is composed of more massive merged galaxies and has a larger in-situ fraction. The ICL mass fraction increases weakly with cluster mass, declines with concentration and increases with time since the BCGs most recent major merger. The ICL is bluer and more metal-poor than the BCG, but there is no significant difference in the age of the material. Universally, BCG+ICL systems have negative colour and metallicity gradients. The ICL and BCG share a high fraction of progenitor galaxies, but the most significant progenitor is frequently not shared. Conclusions. ICL properties and formation are tied to the formation histories of the host cluster and BCG, and thus their properties are individual to each system. Although the ICL and BCG coevolve, they have distinct formation histories and properties.

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arXiv2026

Mapping the Distorted Dark Matter Distribution of the LMC-SMC System Prior to Milky Way Infall with Basis Function Expansions

The SMC orbits within the LMC's dark matter (DM) halo in a $\sim$1:10 mass-ratio encounter. The LMC:Milky Way (MW) interaction is also $\sim$1:10, and is expected to perturb the MW's DM distribution. However, no framework exists to quantify the severity of these perturbations over multiple pericenters and longer periods of time, such as the LMC-SMC interaction history. We construct basis function expansions of a high-resolution \textit{N}-body simulation of the Clouds interacting in isolation and analyze their DM distributions at an epoch approximating the time of their infall to the MW. Our goal is to quantify how the Clouds distort each other's DM distributions \textit{without} the MW. The LMC halo's response to the SMC includes a $\sim 20$ kpc long dynamical friction wake and the displacement of the LMC's density center during each SMC pericenter, which produces two overdensities in the LMC halo (at $\sim$60 and $\sim$100 kpc) at MW infall. The SMC's tidal radius at infall is just $\sim4$ kpc, at which point the SMC has lost two-thirds of its initial DM mass to the LMC. The distortions to the Clouds' halos produce a highly asymmetric acceleration field. Accurate orbit integration in the LMC-SMC system must account for the time-dependent shapes of both halos. The SMC-induced perturbations in the LMC DM halo resemble the MW-LMC system, and persist over multiple SMC pericenters. We conclude that 1:10 satellite-host encounters induce characteristic deformations in both DM halos across host-mass scales, with implications for merger rates and tests of DM models.

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arXiv2026

On the origin of counterrotating stellar disks in TNG50. I

Understanding galaxy evolution is key to explaining the structures we observe in the present-day Universe. Counterrotating stellar disks (CRDs), i.e. co-spatial stellar disks rotating with opposite angular momentum, have been proposed as signatures of past accretion events. Therefore, they constitute potentially valuable tracers of galactic assembly. We aim to investigate the properties, formation, and significance of CRDs in a sample of Milky Way mass galaxies using the IllustrisTNG cosmological simulations. We select 260 central late-type galaxies (i.e. $M_{\rm tot} \approx 10^{12}$, $D/T>0.5$, $N_{\rm star}>10^5$). For each galaxy, we measure the circularity of its stellar particles and define the CRD by considering all particles with circularity $ε< -0.7$, which are located within the spatial extension of the main disk. We then characterize the mass fraction, spatial extent, and star formation history of the CRDs. Out of the 260 galaxies, we find that 26 host significant CRDs (i.e. contributing at least 1\% of the total stellar mass of the disk). This means that CRDs are rare, consistent with the results from observations. We also find that the most of the CRDs are compact (i.e. 88\%), in-situ dominated (i.e.73\%), and exhibit bursty SFHs whose peaks often coincide with external perturbations. This means that external perturbations are able to catalyze star formation, even when a majority of the CRD's star population is in-situ. Finally, we find that a variety of formation pathways can lead to CRDs, including interaction-induced in-situ bursts and smooth accretion of misaligned gas. Overall, our results suggest that CRDs are rare but diverse in origin. In most cases, their formation is linked to the accretion of retrograde gas, either through mergers or environmental inflow, suggesting that these structures are sensitive tracers of the galaxy's past accretion history.

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arXiv2026

Stirring Things Up: Bar-induced substructures in the stellar halo of a cosmological Milky Way analogue

The stellar halo of the Milky Way contains the remnants of past accretion events, which could be detectable as substructures in the classical integrals of motion space, such as energy and angular momentum (E-Lz). However, our galaxy also contains a non-axisymmetric stellar bar, which traps stars in resonant orbits, leading to substructures in phase-space. Using a high-resolution magneto-hydrodynamic cosmological zoom-in simulation of a Milky Way analogue, we explore the connection between the bar and the accreted stellar halo. We find that the bar induces prominent substructures, or "ridges", in E-Lz, caused by the resonances. The most pronounced of these is caused by the corotation and the retrograde 1:1 resonances, with weaker ridges visible due to the prograde 1:1 and outer Lindblad resonance. The ridges are present across much of the stellar halo, with variations in radius due to the morphology of different orbital families. We explore the scattering of orbits at the resonances, finding that stars trapped at the 1:1 retrograde resonance become more circularised and have more negative angular momentum. Additionally, stars can move between the corotation and retrograde 1:1 families, thus alternating between prograde and retrograde motion. Due to these scatterings and the pre-existing metallicity gradients in the accreted population, the bar-induced substructures have distinct metallicities compared to stars in the surrounding phase-space. Our results suggest the need for caution when searching the Milky Way stellar halo for accreted substructures in both integral of motions and chemical spaces, since these can be induced by internal perturbations.

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arXiv2025

Auriga Streams III: the mass-metallicity relation does not rule out tidal mass loss in Local Group satellites

The mass-metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. We show that the small scatter in this relation, which has been used to argue against tidal mass loss in Local Group satellites, is consistent with the level of disruption in the Auriga simulations. For every accreted system in Auriga, we compute stellar masses and metallicities two ways: considering the total system (bound + lost material) and only considering the progenitor. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the progenitor, the tidally evolved mass-metallicity relation has similar scatter ($\sim$0.27 dex) as observed for the Local Group satellites ($\sim$0.23 dex). Satellites that lie above the relation have experienced substantial mass loss and typically have low metallicity for their total stellar mass. Even satellites that fall exactly on the evolved relation can lose over half of their stellar mass. Only satellites substantially below the evolved relation are reliably intact. Based on their offset from the observed relation, we predict which Milky Way and M31 satellites have tidal tails waiting to be discovered.

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arXiv2025

Auriga Superstars: Improving the resolution and fidelity of stellar dynamics in cosmological galaxy simulations

Cosmological hydrodynamical simulations have become an indispensable tool to understand galaxies. However, computational constraints still severely limit their numerical resolution. This not only restricts the sampling of the stellar component and its direct comparison to detailed observations, but also the precision with which it is evolved. To overcome these problems we introduce the \emph{Superstars} method. This method increases the stellar mass resolution in cosmological galaxy simulations in a computationally inexpensive way for a fixed dark matter and gas resolution without altering any global properties of the simulated galaxies. We demonstrate the \emph{Superstars} method for a Milky Way-like galaxy of the Auriga project, improving the stellar mass resolution by factors of $8$ and $64$ at an additional cost of only $10\%$ and $500\%$, respectively. We show and quantify that this improves the sampling of the stellar population in the disc and halo without changing the properties of the central galaxy or its satellites, unlike simulations that change the resolution of all components (gas, dark matter, stars). Moreover, the better stellar mass resolution reduces numerical heating of the stellar disc in its outskirts and keeps substructures in the stellar disc and inner halo more coherent. It also makes lower mass and lower surface brightness structures in the stellar halo more visible. The \emph{Superstars} method is straightforward to incorporate in any cosmological galaxy simulation that does not resolve individual stars.

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arXiv2025

The distribution and origin of metals in simulated Milky Way-like galaxies

In this study, we investigate the distribution and origin of chemical elements in different stellar components of simulated Milky Way-like galaxies in relation to their mass assembly history, stellar age, and metallicity. Using a sample of 23 simulated galaxies from the Auriga project, we analysed the evolution of heavy elements produced by stellar nucleosynthesis. To study the chemical evolution of the stellar halo, bulge, and warm and cold discs of the model galaxies, we applied a decomposition method to characterise the distribution of chemical elements at $z=0$ and traced back their origin. Our findings indicate that each stellar component has a distinctive chemical trend despite galaxy-to-galaxy variations. Specifically, stellar haloes are $α$-enhanced relative to other components, representing the oldest populations, with [Fe/H] ~ $-$0.6 and a high fraction of ex situ stars of ~ 50%. They are followed by the warm ([Fe/H] ~ $-$0.1) and cold ([Fe/H] ~ 0) discs, with in situ fractions of ~ 90% and ~ 95%, respectively. Alternatively, bulges are mainly formed in situ but host more diverse stellar populations, with [Fe/H] abundance extending over ~ 1 dex around the solar value. We conclude that one of the main drivers shaping the chemical properties of the galactic components in our simulations is the age-metallicity relation. The bulges are the least homogeneous component of the sample, as they present different levels of contribution from young stars in addition to the old stellar component. Conversely, the cold discs appear very similar in all chemical properties, despite important differences in their typical formation times. Finally, we find that a significant fraction of stars in the warm discs were in the cold disc at birth. We discuss the possible connections of this behaviour with the development of bars and interactions with satellites.

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arXiv2025

Auriga Streams I: disrupting satellites surrounding Milky Way-mass haloes at multiple resolutions

In a hierarchically formed Universe, galaxies accrete smaller systems that tidally disrupt as they evolve in the host's potential. We present a complete catalogue of disrupting galaxies accreted onto Milky Way-mass haloes from the Auriga suite of cosmological magnetohydrodynamic zoom-in simulations. We classify accretion events as intact satellites, stellar streams, or phase-mixed systems based on automated criteria calibrated to a visually classified sample, and match accretions to their counterparts in haloes re-simulated at higher resolution. Most satellites with a bound progenitor at the present day have lost substantial amounts of stellar mass -- 67 per cent have $f_\text{bound} < 0.97$ (our threshold of lost stellar mass to no longer be considered intact), while 53 per cent satisfy a more stringent $f_\text{bound} < 0.8$. Streams typically outnumber intact systems, contribute a smaller fraction of overall accreted stars, and are substantial contributors at intermediate distances from the host centre ($\sim$0.1 to $\sim$0.7$R_\text{200m}$, or $\sim$35 to $\sim$250 kpc for the Milky Way). We also identify accretion events that disrupt to form streams around massive intact satellites instead of the main host. Streams are more likely than intact or phase-mixed systems to have experienced preprocessing, suggesting this mechanism is important for setting disruption rates around Milky Way-mass haloes. All of these results are preserved across different simulation resolutions, though we do find some hints that satellites disrupt more readily at lower resolution. The Auriga haloes suggest that disrupting satellites surrounding Milky Way-mass galaxies are the norm and that a wealth of tidal features waits to be uncovered in upcoming surveys.

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arXiv2025

Shaping the Milky Way: The interplay of mergers and cosmic filaments

The large-scale morphology of Milky Way (MW)-mass dark matter (DM) halos is shaped by two key processes: filamentary accretion from the cosmic web and interactions with massive satellites. Disentangling their contributions is essential for understanding galaxy evolution and constructing accurate mass models of the MW. We analyze the time-dependent structure of MW-mass halos from zoomed cosmological-hydrodynamical simulations by decomposing their mass distribution into spherical harmonic expansions. We find that the dipole ($\ell=1$) and quadrupole ($\ell=2$) moments dominate the gravitational power spectrum, encoding key information about the halo's shape and its interaction with the cosmic environment. While the dipole reflects transient perturbations from infalling satellites and damps on dynamical timescales, the quadrupole -- linked to the halo's triaxiality -- is a persistent feature. We show that the quadrupole's orientation aligns with the largest filaments, imprinting a long-lived memory on the halo's morphology even in its inner regions ($\sim30$ kpc). At the virial radius, the quadrupole distortion can reach 1-2 times the spherical density, highlighting the importance of environment in shaping MW-mass halos. Using multivariate Singular Spectrum Analysis, we successfully disentangle the effects of satellite mergers and filamentary accretion on quadrupole. We find that the quadrupolar response induced by LMC-mass satellites has an order of magnitude larger gravitational power than in spherically symmetric MW models. This highlights the need for models that incorporate the MW's asymmetry and time-evolution, with direct consequences for observable structures such as disk warps, the LMC-induced wake, and stellar tracers -- particularly in the era of precision astrometry.

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arXiv2025

The formation and evolution of Supermassive disks in IllustrisTNG

Supermassive disks are outstanding galaxies whose formation and evolution are still poorly understood. They comprise a large variety of objects, ranging from large, low-surface-brightness galaxies, such as Malin 1, to the most spectacular superluminous spirals. However, we still do not know the physical mechanisms behind its formation, and whether they will be long-lived objects or whether their mass could destroy them in time. We aim to investigate the formation and evolution of these galaxies using the magnetohydrodynamical state-of-the-art simulation IllustrisTNG-100. We defined supermassive disks as galaxies with $λ/ \sqrt{\varepsilon} \geq 0.31$ or 0.71, and with stellar mass log$_{10}M_\star/M_\odot > 10^{11}$. We studied the color, merging history, AGN history, and environment in which these galaxies reside. Supermassive disk galaxies typically experience a quiescent merging history, with $48\%$ experiencing no significant mergers at $z \leq 1$. Their stellar mass growth is driven mainly by star formation, unlike spheroidal galaxies, which require a significant number of mergers to form. Moreover, the mergers experienced by disk galaxies are generally rich in gas content, irrespective of whether they are minor or major events. Supermassive disks exist across various environments, from isolation to clusters, with $\sim 60\%$ inhabiting in isolation or low-mass groups, $\sim 25\%$ residing in massive groups, and $\sim15\%$ residing within galaxy clusters. When studying the evolution of supermassive disks selected at $z=0.5$, we show that when they gain sufficient mass, the probability of them maintaining their disk-like structure up to $z=0$ is relatively high ($\sim 60\%$). Lastly, while AGN significantly influences the regulation of star formation in galaxies, it does not directly alter their morphological structure.

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arXiv2025

Differences in the Physical Properties of Satellite Galaxies within Relaxed and Disturbed Galaxy Groups and Clusters

Galaxy groups and clusters are the most massive collapsed structures in the Universe. Those structures are formed by collapsing with other smaller structures. Groups and cluster mergers provide an appropriate environment for the evolution and transformation of their galaxies. The merging process of groups and clusters can affect the properties of their galaxy populations. Our aim is to characterise the distribution of galaxies' colour, specific star formation rate, quenched galaxy fraction, and gas availability in galaxies bounded to groups and clusters and to examine how these properties relate to the dynamical state of their host environments. We used the most massive halos ($M > 10^{13} M_{\odot}$) in Illustris TNG100 simulations and separated the sample into two categories: relaxed and disturbed halos. This classification was done based on the offset between the position of the Brightest Cluster Galaxy (BCG) and the centre of mass of the gas. Subsequently, we classified their galaxy populations into red and blue galaxies using a threshold derived from a double Gaussian fit to their colour distribution. Our findings reveal differences in physical properties such as colour, star formation rates, and gas availability among satellite galaxies bound to interacting clusters compared to relaxed clusters. Disturbed clusters exhibit more blue, star-forming galaxies than their relaxed counterparts. This discrepancy in the fraction of blue and star-forming galaxies can be attributed to higher gas availability, including hot, diffuse, and condensed gas in satellite galaxies in disturbed clusters compared to relaxed ones. Furthermore, our study shows that during cluster mergers, there are two crucial phases; at the beginning of the interaction, there is an important boost in the star formation rate followed by suppression as the cluster reaches the equilibrium state.

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