Correction to: Prevention is better than cure? Feedback from high specific energy winds in cosmological simulations with <scp>Arkenstone</scp>

Monthly Notices of the Royal Astronomical Society · 2026-02-27 · 1 citations

We deploy the new Arkenstone galactic wind model in cosmological simulations for the first time, allowing us to robustly resolve the evolution and impact of high specific energy winds. In a (25 $h^{-1}$ Mpc)$^3$ box we perform a set of numerical experiments that systematically vary the mass and energy loadings of such winds, finding that their energy content is the key parameter controlling the stellar to dark matter mass ratio. Increasing the mass loading, at fixed energy, actually results in mildly enhanced star formation, counter to prevailing wisdom, due to the wind becoming cooler. Of the simple parametrisations that we test, we find that an energy loading that scales inversely with halo mass best matches a wide range of observations and can do so with mass loadings drastically lower than those in most previous cosmological simulations. In this scenario, much less material is ejected from the interstellar medium. Instead, winds both heat gas in the circumgalactic medium, slowing infall onto the galaxy, and also drive shocks beyond the virial radius, decreasing the halo-scale accretion rate. We can also report that a much lower fraction of the available supernova energy is needed in preventative galaxy regulation than required by ejective wind feedback models such as IllustrisTNG. This is a Learning the Universe collaboration publication.

Mainly on the Plane: Observing the Extended, Ionized Disks of Milky Way Analogs in IllustrisTNG

The Astrophysical Journal · 2026-03-23

Abstract This paper explores the extent to which the circumgalactic medium (CGM) of Milky Way (MW)-like galaxies is located in an extended, ionized, disklike structure. To test this hypothesis, we analyze the spatial and kinematic distributions of different ion species within a sample of MW-like systems in IllustrisTNG. We model commonly observed ions (H I , Mg II , Si IV , C IV , and O VI ) and calculate (1) their angular momentum misalignment from the star-forming disk ( θ ) and (2) the fraction of absorption consistent with galaxy rotation ( f EWcorot ). We find that 63% of Mg ii , 45% of Si iv , 38% of C iv , and 35% of O vi mass along the major axis have kinematics aligned with the galaxy angular momentum axis. We extend this to a mock absorption line survey and quantify f EWcorot . We find that f EWcorot (Mg ii ) ∼ 80% and f EWcorot (O vi ) ∼ 60% at ∼0.5 R 200c , in agreement with recent observational work. We find that in the typical MW analog, there is evidence of cool–warm material in an extended, corotating structure, regardless of whether the angular momentum or observational definition is used. Hence, we expect that the typical MW CGM, especially in the low ions, should be mainly on the plane.

Identifying Signatures of Inflow onto Face-on Galaxies Using the Balmer Decrement

The Astrophysical Journal · 2026-04-07

Abstract Isolated star-forming galaxies require inflows of fresh gas from the surrounding medium to sustain episodes of star formation over time. However, there are very few direct detections of accretion onto external galaxies. Studies in absorption can only observe along limited sightlines, while those in emission can have difficulty distinguishing inflowing gas in the foreground of the galactic disk from similarly Doppler-shifted outflowing gas in the background. We explore the possibility of using the Balmer decrement (H α /H β ) in low-inclination systems as a diagnostic for disentangling the flow geometry in disk-like galaxies. We leverage mock spatial–spectral observations of an isolated Milky Way–mass galaxy simulated using the radiation-hydrodynamics code AREPO-RT and post-processed with the Monte Carlo radiative transfer code COLT. We find that gas components located in front of the disk exhibit systematically lower Balmer decrements than gas embedded in or behind the disk, with a mean front–back offset of Δ(H α /H β ) ≈ –0.14. The ability to differentiate between the disk and far-side components is limited by the extremely clumpy, multiphase dust distribution along the line of sight introducing substantial scatter. Overall, the results provide a useful observational diagnostic of inflow and outflow in dusty face-on galaxies.

Resolving the Unresolved Galactic Winds in Multi-phase Models. I. Methodology and Application

arXiv (Cornell University) · 2026-05-01

Galactic winds shape galaxy evolution; however, the outflowing gas is complex: it consists of multiple ionization phases, and its properties vary spatially. Therefore, methods that combine high-fidelity observations with state-of-the-art galactic-wind models are limited. Here we investigate methods for fitting the column density profiles derived from high-quality outflow observations with the multiphase, multiscale wind model from Fielding &amp; Bryan 2022. We identify three key outflow parameters: the initial hot-phase mass-loading factor ($η_\text{ M,hot,0}$), the initial cool-phase mass-loading factor ($η_\text{ M,cool,0}$), and the initial cool-cloud mass. We obtain good fits for most galaxies, with tight constraints on $η_\text{ M,cool,0}$ and moderate constraints on the other two parameters. We find the inferred $η_\text{ M,cool,0}$ and $η_\text{ M,hot,0}$ are mostly of order unity, with significant scatter. The constraints on $η_\text{ M,hot,0}$ suggest that the interaction between the cool and hot phases allows us to indirectly constrain the properties of the hot wind from cool-outflow observations. The model also predicts various radial trends. First, for all galaxies, the cool-phase outflow velocity increases between $1-2$ times of the half-light radius, then reaches a plateau. Second, most galaxies exhibit increasing $η_\text{ M,cool}$ and decreasing $η_\text{ M,hot}$ with radius, with a few showing the reverse trends. These results are effective, model-conditional constraints, and are consistent with other recent multiphase simulations and observations. This highlights that the velocity-radius mapping encoded in UV absorption profiles enables recovery of outflow spatial structures from spatially integrated spectra. Our method paves the way for future broad parameter studies and guides updates of outflow simulations in future work.

A <scp>eos</scp> Is Mixing It Up: The (In)homogeneity of Metal Mixing Following Population III Star Formation

The Astrophysical Journal · 2026-04-23

Abstract Stellar surface abundances are records of the state of the gas from which stars formed and thus trace how individual elements have mixed into the surrounding medium following their ejection from stars. In this work, we test the common assumption of instantaneous and homogeneous metal mixing during the formation of the first Population II stars by characterizing the chemical homogeneity of the gas in simulated star-forming environments enriched by Population III stellar feedback. Testing the homogeneity of metal mixing in this time period is necessary for understanding the spread of abundances in the most metal-poor stars and the (in)homogeneity of individual sites of star formation. Using A eos , a suite of star-by-star cosmological simulations, we quantify how gas abundances change over space and time relative to Population II stellar abundances using Mahalanobis distances, a measure of covariance-normalized dissimilarity. We find that the homogeneous mixing assumption holds only within ∼100 pc of a star-forming region and ∼7 Myr following the star formation event. Beyond this regime, deviations between stellar and gas abundances increase until they become indistinguishable from assuming a homogeneous mix of metals averaged over the initial mass function. This highlights the limited applicability of assuming instantaneous and homogeneous mixing in realistic halo environments at high redshift. We identify critical mixing scales that are necessary to explore chemical evolution in the early Universe. These scales can be applied to determine the precision needed for accurate chemical tagging of observed data and to explore parameter space with analytical models.

What Suppresses Star Formation in Bulge-dominated Early-type Galaxies?

The Astrophysical Journal · 2026-05-18

Abstract We investigate the physical origin of star formation suppression in gas-rich early-type galaxies (ETGs) using five high-resolution hydrodynamical idealized galaxy simulations, performed with the moving-mesh code AREPO . These simulations include one Milky Way–like galaxy and four ETGs, of which one ETG is found to have significantly less star formation despite a substantial molecular gas reservoir. We apply a modified virial theorem to the overdensities in each galaxy to quantify the forces regulating their stability and thus star formation. We find evidence that, in the suppressed galaxy, strong Coriolis forces driven by elevated galactic shear may inhibit gravitational collapse. This is caused by the galaxy’s high central compactness, providing a physical mechanism for the suppression of star formation that does not require the removal of molecular gas. In contrast, less-compact ETGs host more gravity-dominated clouds and therefore exhibit higher star formation rates. However, this gravitational stability occurs without significantly increasing the classical Toomre- Q parameter or velocity dispersion, and therefore, new criteria or tracers for suppressed star formation may be needed. We also discuss the impact of our choice of overdensity scale and connections to observations of molecular clouds.

Blue Monsters and Dusty Descendants: Reconciling UV and IR Emission from Galaxies from <i>z</i>  ∼ 7, up to <i>z</i> = 14

The Astrophysical Journal · 2026-05-22

Abstract Recent JWST observations reveal massive, UV-bright galaxies at z &gt; 10 with little apparent dust attenuation, whereas Atacama Large Millimeter/submillimeter Array detections at z ≃ 7 show similarly massive systems that are already dust-rich and IR-luminous. This raises a fundamental question: can a single physical model for star formation and dust production explain both populations across cosmic time? We address this using a minimal, physically motivated framework with only two free parameters—the instantaneous star formation efficiency ( ϵ ⋆ ) and the dust yield per Type II supernova ( y d )—and predict the rest-frame UV and IR luminosity functions (LFs) from z ≃ 14 to 7. For a uniform interstellar medium (ISM), we find a UV–IR tension at the bright end of the LFs at z ≥ 7. The UV LF requires low dust yields ( y d ≲ 0.01 M ⊙ ), while the z = 7 IRLF requires high yields ( y d ∼ 0.1 M ⊙ ) unless the star formation efficiency is boosted above ϵ ⋆ ≈ 5%–10%. We show that incorporating a porous, turbulent ISM largely resolves this tension: turbulence opens low-column-density sight lines that enhance the UV escape fraction while leaving the total absorbed energy—and thus the IR luminosity—nearly unchanged once radiative-transfer-induced flattening of the attenuation curve is included. Large-grain dust distributions, while reducing UV opacity, become secondary once ISM porosity and radiative transfer are taken into account. At z &gt; 10, however, even strong turbulence cannot reproduce the bright end of the UVLF at high dust yield. This could be resolved by efficient dust removal in early massive systems or substantial ISM dust growth by z ≃ 7. Our results highlight dust physics as a key lever for interpreting the rapidly growing UV and IR observational constraints within the broader context of early galaxy formation.

The Entangled Feedback Impacts of Supernovae in Coarse- versus High-Resolution Galaxy Simulations

ArXiv.org · 2025-10-02

It is often understood that supernova (SN) feedback in galaxies is responsible for regulating star formation and generating gaseous outflows. However, a detailed look at their effect on the local interstellar medium (ISM) on small mass scales in simulations shows that these processes proceed in clearly distinct channels. We demonstrate this finding in two independent simulations with solar-mass resolution, LYRA and RIGEL, of an isolated dwarf galaxy. Focusing on the immediate environment surrounding SNe, our findings suggest that the large-scale effect of a given SN on the galaxy is best predicted by its immediate local density. Outflows are driven by SNe in diffuse regions expanding to their cooling radii on large ($\sim$ kpc) scales, while dense star-forming regions are disrupted in a localized (\sim pc) manner. However, these separate feedback channels are only distinguishable at very high numerical resolutions capable of following scales $\ll 10^3 M_\odot$. On larger scales, ISM densities are greatly mis-estimated, and differences between local environments of SNe become severely washed out. We demonstrate the practical implications of this effect by comparing with a mid-resolution simulation ($M_{\rm ptcl.} \sim 200 M_\odot$) of the same dwarf using the SMUGGLE model. The coarse-resolution simulation cannot self-consistently determine whether a given SN is responsible for generating outflows or suppressing star formation, suggesting that emergent galaxy physics such as star formation regulation through hot-phase outflows is fundamentally unresolvable by subgrid stellar feedback models, without appealing directly to simulations with highly resolved ISM.

Modelling cosmic rays at AGN jet-driven shock fronts

Monthly Notices of the Royal Astronomical Society · 2025-11-20 · 1 citations

ABSTRACT Feedback from active galactic nuclei (AGNs) is a key physical mechanism proposed to regulate galaxy formation and suppress star formation, primarily in massive galaxies. Cosmic rays (CRs) associated with AGN jets can efficiently suppress cooling flows and quench star formation, but the locus of CR production and their coupling to gas are crucial to self-regulation. We conduct high-resolution, non-cosmological magnetohydrodynamic (MHD) simulations of a massive $10^{14} {\rm M_\odot }$ halo using the FIRE-2 (Feedback In Realistic Environments) stellar feedback model. We explore AGN jet feedback with CRs by varying the CR energy fraction in jets, the CR coupling sites (in the vicinity of the black hole versus at the shock fronts of large-scale jet cocoons), and jet precession parameters. Our findings indicate that injecting CRs near the black hole efficiently inhibits accretion by lowering the local gas density before the jet propagates to large radii. This produces episodic accretion and leaves the jet with insufficient energy flux to reach large radii and impact cooling flows. By contrast, injecting CRs at the shock front of the jet cocoon sustains a higher jet energy flux for longer and disperses CRs to larger radii. This configuration more effectively suppresses the cooling flow. The period and angle of jet precession influence shock-front positions. We identify an optimal range of precession periods of order tens of Myr that places shocks in the inner circumgalactic medium (CGM), where cooling flows are most severe. We report that this configuration most effectively suppresses cooling flows and quenches star formation.

Aeos is Mixing it Up: The (In)homogeneity of Metal Mixing Following Population III Star Formation

ArXiv.org · 2025-09-16

Stellar surface abundances are records of the state of the gas from which stars formed, and thus trace how individual elements have mixed into the surrounding medium following their ejection from stars. In this work, we test the common assumption of instantaneous and homogeneous metal mixing during the formation of the first Population II stars by characterizing the chemical homogeneity of the gas in simulated star-forming environments enriched by Population III stellar feedback. Testing the homogeneity of metal mixing in this time period is necessary for understanding the spread of abundances in the most metal-poor stars, and the (in)homogeneity of individual sites of star formation. Using Aeos, a suite of star-by-star cosmological simulations, we quantify how gas abundances change over space and time relative to Population II stellar abundances using Mahalanobis distances, a measure of covariance-normalized dissimilarity. We find that the homogeneous mixing assumption holds only within $\sim100$ pc of a star-forming region and $\sim 7$ Myr following the star formation event. Beyond this regime, deviations between stellar and gas abundances increase until they become indistinguishable from assuming a homogeneous mix of metals averaged over the initial mass function. This highlights the limited applicability of assuming instantaneous and homogeneous mixing in realistic halo environments at high redshift. We identify critical mixing scales that are necessary to explore chemical evolution in the early Universe. These scales can be applied to determine the precision needed for accurate chemical tagging of observed data and to explore parameter space with analytical models.