arXiv subjects

M. Vogelsberger

Publications and source records attributed to M. Vogelsberger.

13 recordsLinked to original sources

arXiv2026

Strong Stellar Diffusion from Wave DM Cosmological Simulation and Potential Unified Origin for dSphs, UFGs, and UDGs

Our $\psi$DM simulations predict that stars diffuse throughout dark matter halos over the Hubble time through a random walk driven by the wave perturbations intrinsic to $\psi$DM. The resulting stellar distribution locally follows a Gaussian profile (Sersic index $n=0.5$), as expected from the central limit theorem, expanding as $R_{1/2}(t)\simeq(\hbar/m_\psi)^{0.5}\sqrt{t}$, in good agreement with the core--halo profiles of typical $\psi$DM dwarf spheroidal galaxies. The strength of this diffusion depends on halo mass and the corresponding soliton, naturally producing progressively more diffuse stellar systems in more massive halos. The observed continuity from faint dwarfs and compact dwarf spheroidals to ultra-diffuse galaxies can therefore be interpreted as an age sequence, with later-forming dwarfs experiencing less diffusion and thus remaining smaller and brighter. Stellar scattering arises from the random walk of the soliton, gradually transporting stars from the dense central core into the outer halo, creating the extended stellar envelopes observed around Local Group dwarfs. Rather than being unique to Ultra-Diffuse Galaxies (UDGs), this wave-driven stellar diffusion may provide a unified mechanism explaining galaxy structure across a vast mass range, from ultra-faint dwarfs to the most massive UDGs, without requiring distinct formation channels or "failed galaxy" scenarios. The diffuse stellar halos and globular cluster distributions recently revealed by Euclid may therefore represent direct observational signatures of the granular dynamics of wave dark matter.

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arXiv2026

Probing the kinematics of the Local Group with chemically enriched gas in the Hestia simulations

We present a study of the gas kinematics within the Hestia project, a state-of-the-art set of simulations of the Local Group, with a particular focus on the velocity patterns of different ions and the large-scale motion of gas and galaxies towards the Local Group barycentre. Using two high-resolution Hestia runs, we examine the distribution and velocities of H I, C IV, Si III, O VI, O VII, and O VIII and their imprints on sightlines observed from the Sun's location in different reference frames. To mimic observational strategies, we assess the contribution of rotating disc gas, assuming simple kinematic and geometrical considerations. Our results indicate that local absorption features in observed sightlines most likely trace material in the circumgalactic medium of the Milky Way. Some sightlines, however, show that intragroup material could be more easily observed towards the barycentre, which defines a preferred direction in the sky. In particular, H I, Si III, and C IV roughly trace cold gas inside the Milky Way and Andromeda haloes, as most of their mass flux occurs within the virial region of each galaxy, while oxygen high ions mostly trace hot halo and intragroup gas, with comparable mass fluxes in the Local Group outskirts and the circumgalactic medium of the two main galaxies. Additionally, we find that pressures traced by different ionic species outside the Milky Way halo show systematically higher values towards the barycentre direction in contrast to its antipode in the sky. Kinematic imprints of the global motion towards the barycentre can be seen at larger distances for all ionic species as the Milky Way rams into material in the direction of Andromeda, with gas towards the anti-barycentre lagging behind.

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arXiv2026

CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations IV. Testing warm dark matter cosmologies with galaxy scaling relations: A joint simulation-observation study using DREAMS simulations

Small-scale discrepancies in the standard Lambda cold dark matter paradigm have motivated the exploration of alternative dark matter (DM) models, such as warm dark matter (WDM). We investigate the constraining power of galaxy scaling relations on cosmological, astrophysical, and WDM parameters through a joint analysis of hydrodynamic simulations and observational data. Our study is based on the DREAMS project and combines large-volume uniform-box simulations with high-resolution Milky Way zoom-in runs in a $Λ$WDM cosmology. To ensure consistency between the different simulation sets, we apply calibrations to account for resolution effects, allowing us to exploit the complementary strengths of the two suites. We compare simulated relations, including stellar size, DM mass and fraction within the stellar half-mass radius, and the total-to-stellar mass ratio, with two complementary galaxy samples: the SPARC catalog of nearby spirals and the LVDB catalog of dwarf galaxies in the Local Volume. Using a bootstrap-based fitting procedure, we show that key cosmological parameters ($Ω_m$, $σ_8$) and supernova feedback strength can be recovered with good accuracy, particularly from the uniform-box simulations. While the WDM particle mass remains unconstrained, the zoom-in simulations reveal subtle WDM-induced trends at low stellar masses in both the DM mass and total-to-stellar mass ratio. We also find that the galaxy stellar mass function exhibits a measurable dependence on the WDM particle mass below log10(M_*/Msun) <~ 8, which appears separable from the impact of feedback, suggesting it as a promising complementary probe. Our results highlight the importance of combining multi-resolution simulations with diverse observational datasets to jointly constrain baryonic processes and DM properties.

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arXiv2026

The AIDA-TNG project: 3D halo shapes

Context. The shapes of dark matter halos can be used to constrain the fundamental properties of dark matter. In standard Cold Dark Matter (CDM) cosmologies, halos are typically triaxial, with a preference for prolate configurations, particularly at low masses and high redshift. Aims. We focus on the characterization of total matter 3D shape in alternative dark matter models, such as Self-Interacting Dark Matter (SIDM) and Warm Dark Matter (WDM). These scenarios predict different structural properties due to collisional effects or the suppression of small-scale power. Methods. We measure the different halo component shapes - dark matter, stars and gas - at various radii from the center in the AIDA-TNG (Alternative Interacting Dark Matter and Astrophysics - TNG), which is a suite of high-resolution cosmological simulations built upon the IllustrisTNG framework. The intent is to systematically study how different dark matter models - specifically, SIDM and WDM - affect galaxy formation and the structure of dark matter halos, when realistic baryonic physics is also included. Results. SIDM models tend to produce rounder and more isotropic halos, especially in the inner regions, as a result of momentum exchange between dark matter particles. WDM halos are also slightly more spherical than their CDM counterparts, and are typically less concentrated. In all cases, the inclusion of self-consistent baryonic physics makes the central regions of all halos rounder, while still revealing clear distinctions among the various dark matter models. Conclusions. The general framework presented in this work, based on the 3D halo shape, can be useful to interpret multi-wavelength data analyses of galaxies and clusters.

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arXiv2025

Infalling ultra-faint dwarfs as emissaries of the Axiverse

Recent discoveries of ultra-faint dwarf galaxies (UFDs) infalling onto the Milky Way, namely Leo K \& M at $r \simeq 450$kpc, considerably strengthens the case that UFDs constitute a distinct galaxy class that is inherently smaller and fainter, and metal-poorer than the classical dwarf spheroidals (dSph). This distinction is at odds with the inherent continuity of galaxy halo masses formed under scale-free gravity for any standard dark-matter (DM) model. Here, we show that distinct galaxy classes do evolve in cosmological simulations of multiple light bosons representing the ``Axiverse'' proposal of string theory, where a discrete mass spectrum of axions is generically predicted to span many decades in mass. In this context, the observed UFD class we show corresponds to a relatively heavy boson of $3\times 10^{-21}$ eV, including Leo K \& M, whereas a lighter axion of $10^{-22}$ eV comprises the bulk of DM in all larger galaxies including the dSphs. Although Leo M is larger in size than Leo K, we predict its velocity dispersion to be smaller $(\simeq 1.7$km/s) than that of Leo K $(\simeq 4.5$km/s) because of the inverse de Broglie scale dependence on momentum. This scenario can be definitively tested using millisecond pulsars close to the Galactic center, where the Compton frequencies of the heavy and light bosons imprint monotone timing residuals that may be detected by the Square Kilometre Array (SKA) on timescales of approximately one week and four months, respectively.

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arXiv2024

Properties of the Line-of-Sight Velocity Field in the Hot and X-ray Emitting Circumgalactic Medium of Nearby Simulated Disk Galaxies

The hot, X-ray-emitting phase of the circumgalactic medium of massive galaxies is believed to be the reservoir of baryons from which gas flows onto the central galaxy and into which feedback from AGN and stars inject mass, momentum, energy, and metals. These effects shape the velocity fields of the hot gas, which can be observed via the Doppler shifting and broadening of emission lines by X-ray IFUs. In this work, we analyze the gas kinematics of the hot circumgalactic medium of Milky Way-mass disk galaxies from the TNG50 simulation with synthetic observations to determine how future instruments can probe this velocity structure. We find that the hot phase is often characterized by outflows from the disk driven by feedback processes, radial inflows near the galactic plane, and rotation, though in some systems the velocity field is more disorganized and turbulent. With a spectral resolution of $\sim$1 eV, fast and hot outflows ($\sim$200-500 km s$^{-1}$) can be measured, depending on the orientation of the galaxy on the sky. The rotation velocity of the hot phase ($\sim$100-200 km s$^{-1}$) can be measured using line shifts in edge-on galaxies, and is slower than that of colder gas phases but similar to stellar rotation velocities. By contrast, the slow inflows ($\sim$50-100 km s$^{-1}$) are difficult to measure in projection with these other components, but may be detected in multi-component spectral fits. We find that the velocity measured is sensitive to which emission lines are used. Measuring these flows will constrain theories of how the gas in these galaxies evolves.

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arXiv2022

Introducing the THESAN project: radiation-magnetohydrodynamic simulations of the epoch of reionization

We introduce the THESAN project, a suite of large volume (L = 95.5 cMpc) radiation-magnetohydrodynamic simulations that simultaneously model the large-scale statistical properties of the IGM during reionization and the resolved characteristics of the galaxies responsible for it. The flagship simulation has dark matter (DM) and baryonic mass resolutions of $3.1 \times 10^6$ $M_\odot$ and $5.8 \times 10^5 $ $M_\odot$, respectively. The gravitational forces are softened on scales of 2.2 ckpc with the smallest cell sizes reaching 10 pc at z=5.5, enabling predictions down to the atomic cooling limit. The simulations use an efficient radiation hydrodynamics solver (AREPO-RT) that precisely captures the interaction between ionizing photons and gas, coupled to well-tested galaxy formation (IllustrisTNG) and dust models to accurately predict the properties of galaxies. Through a complementary set of medium resolution simulations we investigate the changes to reionization introduced by different assumptions for ionizing escape fractions, varying DM models, and numerical convergence. The simulations produce realistic reionization histories that match the observed evolution of the global neutral hydrogen fraction and electron scattering optical depth to reionization. They also match a wealth of high-redshift observationally inferred data, including the stellar-to-halo-mass relation, stellar mass function, star formation rate density, and the mass-metallicity relation, despite the galaxy formation model being mainly calibrated at z=0. We demonstrate that different reionization models give rise to varied bubble size distributions that imprint unique signatures on the 21cm emission, especially on the slope of the power spectrum at large spatial scales, enabling current and upcoming 21cm experiments to accurately characterise the sources that dominate the ionizing photon budget. [abridged]

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arXiv2022

The THESAN project: Lyman-alpha emission and transmission during the Epoch of Reionization

The visibility of high-redshift Lyman-alpha emitting galaxies (LAEs) provides important constraints on galaxy formation processes and the Epoch of Reionization (EoR). However, predicting realistic and representative statistics for comparison with observations represents a significant challenge in the context of large-volume cosmological simulations. The THESAN project offers a unique framework for addressing such limitations by combining state-of-the-art galaxy formation (IllustrisTNG) and dust models with the Arepo-RT radiation-magneto-hydrodynamics solver. In this initial study we present Lyman-alpha centric analysis for the flagship simulation that resolves atomic cooling haloes throughout a (95.5 cMpc)^3 region of the Universe. To avoid numerical artifacts we devise a novel method for accurate frequency-dependent line radiative transfer in the presence of continuous Hubble flow, transferable to broader astrophysical applications as well. Our scalable approach highlights the utility of LAEs and red damping-wing transmission as probes of reionization, which reveal nontrivial trends across different galaxies, sightlines, and frequency bands that can be modelled in the framework of covering fractions. In fact, after accounting for environmental factors influencing large-scale ionized bubble formation such as redshift and UV magnitude, the variation across galaxies and sightlines mainly depends on random processes including peculiar velocities and self-shielded systems that strongly impact unfortunate rays more than others. Throughout the EoR local and cosmological optical depths are often greater than or less than unity such that the exp(-tau) behavior leads to anisotropic and bimodal transmissivity. Future surveys will benefit by targeting both rare bright objects and Goldilocks zone LAEs to infer the presence of these (un)predictable (dis)advantages.

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arXiv2019

A Deep Learning Approach to Galaxy Cluster X-ray Masses

We present a machine-learning approach for estimating galaxy cluster masses from Chandra mock images. We utilize a Convolutional Neural Network (CNN), a deep machine learning tool commonly used in image recognition tasks. The CNN is trained and tested on our sample of 7,896 Chandra X-ray mock observations, which are based on 329 massive clusters from the IllustrisTNG simulation. Our CNN learns from a low resolution spatial distribution of photon counts and does not use spectral information. Despite our simplifying assumption to neglect spectral information, the resulting mass values estimated by the CNN exhibit small bias in comparison to the true masses of the simulated clusters (-0.02 dex) and reproduce the cluster masses with low intrinsic scatter, 8% in our best fold and 12% averaging over all. In contrast, a more standard core-excised luminosity method achieves 15-18% scatter. We interpret the results with an approach inspired by Google DeepDream and find that the CNN ignores the central regions of clusters, which are known to have high scatter with mass.

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arXiv2019

The Hubble Sequence at $z\sim0$ in the IllustrisTNG simulation with deep learning

We analyze the optical morphologies of galaxies in the IllustrisTNG simulation at $z\sim0$ with a Convolutional Neural Network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim12,000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model finds that $\sim95\%$ of the simulated galaxies fall in one the four main classes with high confidence. The mass-size relations of the simulated galaxies divided by morphological type also reproduce well the slope and the normalization of observed relations which confirms the realism of optical morphologies in the TNG suite. However, the Stellar Mass Functions decomposed into different morphologies still show significant discrepancies with observations both at the low and high mass end. We find that the high mass end of the SMF is dominated in TNG by massive disk galaxies while early-type galaxies dominate in the observations according to the CNN classifications. The present work highlights the importance of detailed comparisons between observations and simulations in comparable conditions.

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arXiv2016

The Califa and Hipass velocity function for all morphological galaxy types

The velocity function is a fundamental observable statistic of the galaxy population, similarly impor- tant as the luminosity function, but much more difficult to measure. In this work we present the first directly measured circular velocity function that is representative between 60 < v_circ < 320 km/s for galaxies of all morphological types at a given rotation velocity. For the low mass galaxy population (60 < v_circ < 170 km/s), we use the HIPASS velocity function. For the massive galaxy population (170 < v_circ < 320 km/s), we use stellar circular velocities from the Calar Alto Legacy Integral Field Area Survey (CALIFA). In earlier work we obtained the measurements of circular velocity at the 80% light radius for 226 galaxies and demonstrated that the CALIFA sample can produce volume- corrected galaxy distribution functions. The CALIFA velocity function includes homogeneous velocity measurements of both late and early-type rotation-supported galaxies and has the crucial advantage of not missing gas-poor massive ellipticals that HI surveys are blind to. We show that both velocity functions can be combined in a seamless manner, as their ranges of validity overlap. The resulting observed velocity function is compared to velocity functions derived from cosmological simulations of the z = 0 galaxy population. We find that dark matter-only simulations show a strong mismatch with the observed VF. Hydrodynamic simulations fare better, but still do not fully reproduce observations.

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arXiv2016

The Missing Satellite Problem in 3D

It is widely believed that the large discrepancy between the observed number of satellite galaxies and the predicted number of dark subhalos can be resolved via a variety of baryonic effects which suppress star formation in low mass halos.Supporting this hypothesis, numerous high resolution simulations with star formation, and associated feedback have been shown to reproduce the satellite luminosity function around Milky Way-mass simulated galaxies at redshift zero. However, a more stringent test of these models is their ability to simultaneously match the satellite luminosity functions of a range of host halo masses and redshifts. In this work we measure the luminosity function of faint (sub-Small Magellanic Cloud luminosity) satellites around hosts with stellar masses 10.5$<\log_{10}$M$_*$/M$_\odot<11.5$ to an unprecedented redshift of 1.5. This new measurement of the satellite luminosity function provides powerful new constraining power; we compare these results with predictions from four different simulations and show that although the models perform similarly over-all, no one model reproduces the satellite luminosity function reliably at all redshifts and host stellar masses. This result highlights the continued need for improvement in understanding the fundamental physics that governs satellite galaxy evolution.

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arXiv2010

Assembly History and Structure of Galactic Cold Dark Matter Halos

We use the Aquarius simulation series to study the imprint of assembly history on the structure of Galaxy-mass cold dark matter halos. Our results confirm earlier work regarding the influence of mergers on the mass density profile and the inside-out growth of halos. The inner regions that contain the visible galaxies are stable since early times and are significantly affected only by major mergers. Particles accreted diffusely or in minor mergers are found predominantly in the outskirts of halos. Our analysis reveals trends that run counter to current perceptions of hierarchical halo assembly. For example, major mergers (i.e. those with progenitor mass ratios greater than 1:10) contribute little to the total mass growth of a halo, on average less than 20 per cent for our six Aquarius halos. The bulk is contributed roughly equally by minor mergers and by "diffuse" material which is not resolved into individual objects. This is consistent with modeling based on excursion-set theory which suggests that about half of this diffuse material should not be part of a halo of any scale. Interestingly, the simulations themselves suggest that a significantly fraction is not truly diffuse, since it was ejected from earlier halos by mergers prior to their joining the main system. The Aquarius simulations resolve halos to much lower mass scales than are expected to retain gas or form stars. These results thus confirm that most of the baryons from which visible galaxies form are accreted diffusely, rather than through mergers, and they suggest that only relatively rare major mergers will affect galaxy structure at later times.

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