34 results on '"Springel, Volker"'
Search Results
2. Probing galaxy evolution from $z=0$ to $z\simeq10$ through galaxy scaling relations in three L-Galaxies flavours
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Vani, Akash, Ayromlou, Mohammadreza, Kauffmann, Guinevere, and Springel, Volker
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
We present a comprehensive examination of the three most recent versions of the L-Galaxies semi-analytic galaxy formation model, focusing on the evolution of galaxy properties across a broad stellar mass range ($10^7\:{\rm M}_{\odot}\lesssim{M_\star}\lesssim10^{12}\:{\rm M}_{\odot}$) from $z=0$ to $z\simeq10$. We compare the predictions with the latest multiband data from key astronomical surveys, including SDSS, CANDELS, and COSMOS along with HST, JWST, and ALMA. We assess the models' ability to reproduce various time-dependent galaxy scaling relations for star-forming and quenched galaxies. Key focus areas include global galaxy properties such as stellar mass functions, cosmic star formation rate density, and the evolution of the main sequence of star-forming galaxies. Additionally, we examine resolved morphological properties such as the galaxy mass-size relation, alongside core $(R<1\,{\rm{kpc}})$ and effective $(R
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- 2024
3. The MillenniumTNG Project: Impact of massive neutrinos on the cosmic large-scale structure and the distribution of galaxies
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Hernández-Aguayo, César, Springel, Volker, Bose, Sownak, Frenk, Carlos, Jenkins, Adrian, Barrera, Monica, Ferlito, Fulvio, Pakmor, Rüdiger, White, Simon D. M., Hernquist, Lars, Delgado, Ana Maria, Kannan, Rahul, and Hadzhiyska, Boryana
- Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We discuss the cold dark matter plus massive neutrinos simulations of the MillenniumTNG (MTNG) project, which aim to improve understanding of how well ongoing and future large-scale galaxy surveys will measure neutrino masses. Our largest simulations, $3000\,{\rm Mpc}$ on a side, use $10240^3$ particles of mass $m_{p} = 6.66\times 10^{8}\,h^{-1}{\rm M}_\odot$ to represent cold dark matter, and $2560^3$ to represent a population of neutrinos with summed mass $M_\nu = 100\,{\rm meV}$. Smaller volume runs with $\sim 630\,{\rm Mpc}$ also include cases with $M_\nu = 0\,\textrm{and}\, 300\,{\rm meV}$. All simulations are carried out twice using the paired-and-fixed technique for cosmic variance reduction. We evolve the neutrino component using the particle-based $\delta f$ importance sampling method, which greatly reduces shot noise in the neutrino density field. In addition, we modify the GADGET-4 code to account both for the influence of relativistic and mildly relativistic components on the expansion rate and for non-Newtonian effects on the largest represented simulation scales. This allows us to quantify accurately the impact of neutrinos on basic statistical measures of nonlinear structure formation, such as the matter power spectrum and the halo mass function. We use semi-analytic models of galaxy formation to predict the galaxy population and its clustering properties as a function of summed neutrino mass, finding significant ($\sim 10\%$) impacts on the cosmic star formation rate history, the galaxy mass function, and the clustering strength. This offers the prospect of identifying combinations of summary statistics that are optimally sensitive to the neutrino mass., Comment: 19 pages, 15 figures
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- 2024
4. Percolation Statistics in the MillenniumTNG Simulations
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Regos, Eniko, Springel, Volker, Bose, Sownak, Hadzhiyska, Boryana, and Hernandez-Aguayo, Cesar
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The statistical analysis of cosmic large-scale structure is most often based on simple two-point summary statistics, like the power spectrum or the two-point correlation function of a sample of galaxies or other types of tracers. In contrast, topological measures of clustering are also sensitive to higher-order correlations, and thus offer the prospect to access additional information that may harbor important constraining power. We here revisit one such geometric measure of the cosmic web in the form of the so-called percolation analysis, using the recent MillenniumTNG simulation suite of the LCDM paradigm. We analyze continuum percolation statistics both for high resolution dark matter particle distributions, as well as for galaxy mock catalogues from a semi-analytic galaxy formation model within a periodic simulation volume of 3000 Mpc on a side. For comparison, we also investigate the percolation statistics of random particle sets and neutrino distributions with two different summed particle masses. We find that the percolation statistics of the dark matter distribution evolves strongly with redshift and thus clustering strength, yielding progressively lower percolation threshold towards later times. However, there is a sizable residual dependence on numerical resolution which we interpret as a residual influence of different levels of shot noise. This is corroborated by our analysis of galaxy mock catalogues whose results depend on sampling density more strongly than on galaxy selection criteria. While this limits the discriminative power of percolation statistics, our results suggest that it still remains useful as a complementary cosmological test when controlled for sampling density., Comment: 14 pages, 12 figures, accepted by ApJ, updated to match published version
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- 2024
5. Improving the Accuracy of Halo Mass Based Statistics For Fast Approximate N-body Simulations
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Wu, Yiheng, Guo, Hong, and Springel, Volker
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
Approximate N-body methods, such as FastPM and COLA, have been successful in modelling halo and galaxy clustering statistics, but their low resolution on small scales is a limitation for applications that require high precision. Full N-body simulations can provide better accuracy but are too computationally expensive for a quick exploration of cosmological parameters. This paper presents a method for correcting distinct haloes identified in fast N-body simulations, so that various halo statistics improve to a percent level accuracy. The scheme seeks to find empirical corrections to halo properties such that the virial mass is the same as that of a corresponding halo in a full N-body simulation. The modified outer density contour of the corrected halo is determined on the basis of the FastPM settings and the number of particles inside the halo. This method only changes some parameters of the halo finder, and does not require any extra CPU-cost. We demonstrate that the adjusted halo catalogues of FastPM simulations significantly improve the precision of halo mass-based statistics from redshifts $z=0.0$ to $1.0$, and that our calibration can be applied to different cosmologies without needing to be recalibrated., Comment: 11pages,15figures
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- 2024
- Full Text
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6. Bursty Star Formation in Dwarfs is Sensitive to Numerical Choices in Supernova Feedback Models
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Zhang, Eric, Sales, Laura V, Marinacci, Federico, Torrey, Paul, Vogelsberger, Mark, Springel, Volker, Li, Hui, Pakmor, Rüdiger, and Gutcke, Thales A
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Simulations of galaxy formation are mostly unable to resolve the energy-conserving phase of individual supernova events, having to resort to subgrid models to distribute the energy and momentum resulting from stellar feedback. However, the properties of these simulated galaxies, including the morphology, stellar mass formed and the burstiness of the star formation history, are highly sensitive to numerical choices adopted in these subgrid models. Using the {\small SMUGGLE} stellar feedback model, we compute idealized simulations of a $M_{\rm vir} \sim 10^{10} \, \msun$ dwarf galaxy, a regime where most simulation codes predict significant burstiness in star formation, resulting in strong gas flows that lead to the formation of dark matter cores. We find that by varying only the directional distribution of momentum imparted from supernovae to the surrounding gas, while holding the total momentum per supernova constant, bursty star formation may be amplified or completely suppressed, and the total stellar mass formed can vary by as much as a factor of $\sim 3$. In particular, when momentum is primarily directed perpendicular to the gas disk, less bursty and lower overall star formation rates result, yielding less gas turbulence, more disky morphologies and a retention of cuspy dark matter density profiles. An improved understanding of the non-linear coupling of stellar feedback into inhomogeneous gaseous media is thus needed to make robust predictions for stellar morphologies and dark matter core formation in dwarfs independent of uncertain numerical choices in the baryonic treatment., Comment: Submitted ApJ; 15 pages, 12 figures; comments welcome
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- 2024
7. Ray-tracing vs. Born approximation in full-sky weak lensing simulations of the MillenniumTNG project
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Ferlito, Fulvio, Davies, Christopher T., Springel, Volker, Reinecke, Martin, Greco, Alessandro, Delgado, Ana Maria, White, Simon D. M., Hernández-Aguayo, César, Bose, Sownak, and Hernquist, Lars
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Weak gravitational lensing is a powerful tool for precision tests of cosmology. As the expected deflection angles are small, predictions based on non-linear N-body simulations are commonly computed with the Born approximation. Here we examine this assumption using ${\small DORIAN}$, a newly developed full-sky ray-tracing scheme applied to high-resolution mass-shell outputs of the two largest simulations in the MillenniumTNG suite, each with a 3000 Mpc box containing almost 1.1 trillion cold dark matter particles in addition to 16.7 billion particles representing massive neutrinos. We examine simple two-point statistics like the angular power spectrum of the convergence field, as well as statistics sensitive to higher order correlations such as peak and minimum statistics, void statistics, and Minkowski functionals of the convergence maps. Overall, we find only small differences between the Born approximation and a full ray-tracing treatment. While these are negligibly small at power-spectrum level, some higher order statistics show more sizable effects; ray-tracing is necessary to achieve percent level precision. At the resolution reached here, full-sky maps with 0.8 billion pixels and an angular resolution of 0.43 arcmin, we find that interpolation accuracy can introduce appreciable errors in ray-tracing results. We therefore implemented an interpolation method based on nonuniform fast Fourier transforms (NUFFT) along with more traditional methods. Bilinear interpolation introduces significant smoothing, while nearest grid point sampling agrees well with NUFFT, at least for our fiducial source redshift, $z_s=1.0$, and for the 1 arcmin smoothing we use for higher-order statistics., Comment: 13 pages, 7 figures, submitted to MNRAS
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- 2024
8. Bar formation and evolution in the cosmological context: Inputs from the Auriga simulations
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Fragkoudi, Francesca, Grand, Robert, Pakmor, Rüdiger, Gómez, Facundo, Marinacci, Federico, and Springel, Volker
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Astrophysics - Astrophysics of Galaxies - Abstract
Galactic bars drive the internal evolution of spiral galaxies, while their formation is tightly coupled to the properties of their host galaxy and dark matter halo. To explore what drives bar formation in the cosmological context and how these structures evolve throughout cosmic history, we use the Auriga suite of magneto-hydrodynamical cosmological zoom-in simulations. We find that bars are robust and long-lived structures, and we recover a decreasing bar fraction with increasing redshift which plateaus around $\sim20\%$ at $z\sim3$. We find that bars which form at low and intermediate redshifts grow longer with time, while bars that form at high redshifts are born `saturated' in length, likely due to their merger-induced formation pathway. This leads to a larger bar-to-disc size ratio at high redshifts as compared to the local Universe. We subsequently examine the multi-dimensional parameter space thought to drive bar formation. We find that barred galaxies tend to have lower Toomre $Q$ values at the time of their formation, while we do not find a difference in the gas fraction of barred and unbarred populations when controlling for stellar mass. Barred galaxies tend to be more baryon-dominated at all redshifts, assembling their stellar mass earlier, while galaxies that are baryon-dominated but that do not host a bar, have a higher ex-situ bulge fraction. We explore the implications of the baryon-dominance of barred galaxies on the Tully-Fisher relation, finding an offset from the unbarred relation; confirming this in observations would serve as additional evidence for dark matter, as this behaviour is not readily explained in modified gravity scenarios., Comment: 21 pages including Appendices, 17 figures, submitted to MNRAS
- Published
- 2024
9. A calibrated model for N-body dynamical friction acting on supermassive black holes
- Author
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Genina, Anna, Springel, Volker, and Rantala, Antti
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
Black holes are believed to be crucial in regulating star formation in massive galaxies, which makes it essential to faithfully represent the physics of these objects in cosmological hydrodynamics simulations. Limited spatial and mass resolution and the associated discreteness noise make following the dynamics of black holes especially challenging. In particular, dynamical friction, which is responsible for driving massive black holes towards the centres of galaxies, cannot be accurately modelled with softened $N$-body interactions. A number of subgrid models have been proposed to mimic dynamical friction or directly include its full effects in simulations. Each of these methods has its individual benefits and shortcomings, while all suffer from a common issue of being unable to represent black holes with masses below a few times the simulated dark matter particle mass. In this paper, we propose a correction for unresolved dynamical friction, which has been calibrated on simulations run with the code KETJU, in which gravitational interactions of black holes are not softened. We demonstrate that our correction is able to sink black holes with masses greater than the dark matter particle mass at the correct rate. We show that the impact of stochasticity is significant for low-mass black holes ($M_{\rm BH} \leq 5 M_{\rm DM}$) and propose a correction for stochastic heating. Combined, this approach is applicable to next generation cosmological hydrodynamics simulations that jointly track galaxy and black hole growth with realistic black hole orbits., Comment: 20 pages, 14 figures, accepted in MNRAS
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- 2024
10. The effect of local photoionization on the galaxy properties and the circumgalactic medium in simulations of Milky Way-sized galaxies
- Author
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Zhu, Bocheng and Springel, Volker
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Astrophysics - Astrophysics of Galaxies - Abstract
In this study, we investigate the impact of local stellar radiation in cosmological zoom simulations of the formation of Milky Way-sized galaxies. We include the radiation field as an additional feedback component that is computed alongside gravity with a tree code in an optically thin approximation. We resimulate the initial conditions of five Milk Way-like systems taken from the Auriga project with and without stellar radiation, and study the effects of local stellar radiation on several properties of the galaxies and the circumgalactic medium (CGM). Similar to previous findings, we observe with our current model that local stellar radiation can modify gas cooling in the CGM and thus suppress star formation and the surface densities of young stars and HI gas, while having little impact on the total gas content. In particular, it also suppresses the peak of the rotation curve and reduces the mass of the stellar bulge. In the CGM region, the young stellar radiation exceeds the external UVB and dominates the radiation field within the virial halo at all redshifts. Nevertheless, we find that the local stellar radiation, as implemented in the current study, has overall little impact on the radial density and temperature profile of the CGM gas. However, for the ion species HI and MgII the column densities within $\sim 0.3\,R_{\rm vir}$ are reduced, while the OVI column density is hardly impacted by the radiation field due to a lack of soft X-ray components in our current model. Additional effects can be expected from the radiation of the central AGN during phases of quasar activity and from soft X-ray sources, which have not yet been included in the simulations of the present study., Comment: 24 pages, 22 figures, accepted for the publication in MNRAS
- Published
- 2024
11. Cosmological gas accretion history onto the stellar discs of Milky Way-like galaxies in the Auriga simulations -- (II) The inside-out growth of discs
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Iza, Federico G., Nuza, Sebastián E., Scannapieco, Cecilia, Grand, Robert J. J., Gómez, Facundo A., Springel, Volker, Pakmor, Rüdiger, Marinacci, Federico, and Fragkoudi, Francesca
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
We investigate the growth of stellar discs in Milky Way-mass galaxies using the magnetohydrodynamical simulations of the Auriga Project in a full cosmological context. We focus on the gas accretion process along the discs, calculating the net, infall and outflow rates as a function of galactocentric distance, and investigate the relation between them and the star formation activity. The stellar distributions of around 70% of the simulated galaxies exhibit an ``inside-out'' pattern, with older (younger) stellar populations preferentially located in the inner (outer) disc regions. In all cases, we find a very tight correlation between the infall, outflow and net accretion rates, as well as between these three quantities and the star formation rate. This is because the amount of gas which is ultimately available for star formation in each radial ring depends not only on the infall rates, but also on the amount of gas leaving the disc in outflows, which directly relates to the local star formation level. Therefore, any of these rates can be used to identify galaxies with inside-out growth. For these galaxies, the correlation between the dominant times of accretion/star formation and disc radius is well fitted by a linear function. We also find that, when averaged over galaxies with formation histories similar to the Milky Way, the simulated accretion rates show a similar evolution (both temporally- and radially-integrated) to the usual accretion prescriptions used in chemical evolution models, although some major differences arise at early times and in the inner disc regions., Comment: 19 pages, 13 figures
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- 2024
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12. The influence of baryons on low-mass haloes
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Zheng, Haonan, Bose, Sownak, Frenk, Carlos S., Gao, Liang, Jenkins, Adrian, Liao, Shihong, Springel, Volker, Wang, Jie, and White, Simon D. M.
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Voids-within-Voids-within-Voids (VVV) project used dark-matter-only simulations to study the abundance and structure of dark matter haloes over the full mass range populated in the standard $\Lambda\mathrm{CDM}$ cosmology. Here we explore how baryonic effects modify these results for $z=0$ halo masses in the range $10^4$ to $10^7~\mathrm{M_\odot}$, below the threshold for galaxy formation. Our main study focuses on three simulations from identical initial conditions at $z=127$, one following dark matter only, one including non-radiative gas, and one additionally including the baryonic physics relevant in this halo mass range (cooling and photoheating). In the non-radiative simulation, above $10^{5.5}~\mathrm{M_\odot}$, halo abundance and internal structure are very similar to the dark-matter-only simulation, and the baryon to dark matter ratio is everywhere close to the cosmic value. At lower mass, this ratio drops and haloes are less concentrated and less massive in the non-radiative case. Test simulations at higher resolution show this to be mainly a resolution effect; the expected drop in baryon content due to residual pressure effects only becomes substantial for $z=0$ haloes below $\sim 10^{2.7}~\mathrm{M_\odot}$. However, gas is heated by reionization at $z=6$ in our "full physics" run, and this results in almost complete expulsion of gas from all haloes in our simulated mass range. This suppresses the halo mass function by $\sim 30 \%$, lowers halo concentration, and consequently weakens the dark matter annihilation signal by $\sim 40-60 \%$., Comment: 12+2 pages, 9 figures
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- 2024
- Full Text
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13. A deep learning model for the density profiles of subhaloes in IllustrisTNG
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Lucie-Smith, Luisa, Despali, Giulia, and Springel, Volker
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We present a machine-learning-based model for the total density profiles of subhaloes with masses $M \gtrsim 7\times 10^8\,h^{-1}{\rm M}_\odot$ in the IllustrisTNG100 simulation. The model is based on an interpretable variational encoder (IVE) which returns the independent factors of variation in the density profiles within a low-dimensional representation, as well as the predictions for the density profiles themselves. The IVE returns accurate and unbiased predictions on all radial ranges, including the outer region profile where the subhaloes experience tidal stripping; here its fit accuracy exceeds that of the commonly used Einasto profile. The IVE discovers three independent degrees of freedom in the profiles, which can be interpreted in terms of the formation history of the subhaloes. In addition to the two parameters controlling the normalization and inner shape of the profile, the IVE discovers a third parameter that accounts for the impact of tidal stripping onto the subhalo outer profile; this parameter is sensitive to the mass loss experienced by the subhalo after its infall onto its parent halo. Baryonic physics in the IllustrisTNG galaxy formation model does not impact the number of degrees of freedom identified in the profile compared to the pure dark matter expectations, nor their physical interpretation. Our newly proposed profile fit can be used in strong lensing analyses or other observational studies which aim to constrain cosmology from small-scale structures., Comment: 13 pages, 7 figures. Minor changes to match version accepted for publication in MNRAS
- Published
- 2024
14. The origin of lopsided satellite galaxy distribution around isolated systems in MillenniumTNG
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Liu, Yikai, Wang, Peng, Guo, Hong, Springel, Volker, Bose, Sownak, Pakmor, Rüdiger, and Hernquist, Lars
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Dwarf satellites in galaxy groups are distributed in an anisotropic and asymmetric manner, which is called the ``lopsided satellite distribution''. This lopsided signal has been observed not only in galaxy pairs but also in isolated systems. However, the physical origin of the lopsided signal in isolated systems is still unknown. In this work, we investigate this in the state-of-the-art hydrodynamical simulation of the MillenniumTNG Project by tracing each system back to high redshift. We find that the lopsided signal is dominated by satellites located in the outer regions of the halo and is also dominated by recently accreted satellites. The lopsided signal originates from the anisotropic accretion of galaxies from the surrounding large-scale structure and that, after accretion, the nonlinear evolution of satellites inside the dark-matter halo weakens the lopsidedness. The signal decreases as cosmic time passes because of a competition between anisotropic accretion and internal evolution within dark matter halos. Our findings provide a useful perspective for the study of galaxy evolution, especially for the origin of the spatial satellite galaxy distributions., Comment: 10 pages, 8 figures, 1 table. Submitted to MNRAS
- Published
- 2024
15. The boundary of cosmic filaments
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Wang, Wei, Wang, Peng, Guo, Hong, Kang, Xi, Libeskind, Noam I., Galarraga-Espinosa, Daniela, Springel, Volker, Kannan, Rahul, Hernquist, Lars, Pakmor, Rudiger, Yu, Haoran, Bose, Sownak, Guo, Quan, Yu, Luo, and Hernandez-Aguayo, Cesar
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
For decades, the boundary of cosmic filaments have been a subject of debate. In this work, we determine the physically-motivated radii of filaments by constructing stacked galaxy number density profiles around the filament spines. We find that the slope of the profile changes with distance to the filament spine, reaching its minimum at approximately 1 Mpc at z = 0 in both state-of-the-art hydrodynamical simulations and observational data. This can be taken as the average value of the filament radius. Furthermore, we note that the average filament radius rapidly decreases from z = 4 to z = 1, and then slightly increases. Moreover, we find that the filament radius depends on the filament length, the distance from connected clusters, and the masses of the clusters. These results suggest a two-phase formation scenario of cosmic filaments. The filaments experience rapid contraction before z = 1, but their density distribution has remained roughly stable since then. The subsequent mass transport along the filaments to the connected clusters is likely to have contributed to the formation of the clusters themselves., Comment: 12 pages, 11 figures, accepted by mnras
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- 2024
- Full Text
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16. Brightest Cluster Galaxy Offsets in Cold Dark Matter
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Roche, Cian, McDonald, Michael, Borrow, Josh, Vogelsberger, Mark, Shen, Xuejian, Springel, Volker, Hernquist, Lars, Pakmor, Ruediger, Bose, Sownak, and Kannan, Rahul
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics ,High Energy Physics - Phenomenology - Abstract
The distribution of offsets between the brightest cluster galaxies of galaxy clusters and the centroid of their dark matter distributions is a promising probe of the underlying dark matter physics. In particular, since this distribution is sensitive to the shape of the potential in galaxy cluster cores, it constitutes a test of dark matter self-interaction on the largest mass scales in the universe. We examine these offsets in three suites of modern cosmological simulations; IllustrisTNG, MillenniumTNG and BAHAMAS. For clusters above $10^{14}\rm{M_\odot}$, we examine the dependence of the offset distribution on gravitational softening length, the method used to identify centroids, redshift, mass, baryonic physics, and establish the stability of our results with respect to various nuisance parameter choices. We find that offsets are overwhelmingly measured to be smaller than the minimum converged length scale in each simulation, with a median offset of $\sim1\rm{kpc}$ in the highest resolution simulation considered, TNG300-1, which uses a gravitational softening length of $1.48\rm{kpc}$. We also find that centroids identified via source extraction on smoothed dark matter and stellar particle data are consistent with the potential minimum, but that observationally relevant methods sensitive to cluster strong gravitational lensing scales, or those using gas as a tracer for the potential can overestimate offsets by factors of $\sim10$ and $\sim30$, respectively. This has the potential to reduce tensions with existing offset measurements which have served as evidence for a nonzero dark matter self-interaction cross section., Comment: 16 pages, 6 figures; v3: OJA published
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- 2024
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17. Overview and public data release of the augmented Auriga Project: cosmological simulations of dwarf and Milky Way-mass galaxies
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Grand, Robert J. J., Fragkoudi, Francesca, Gómez, Facundo A., Jenkins, Adrian, Marinacci, Federico, Pakmor, Rüdiger, and Springel, Volker
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We present an extended suite of the Auriga cosmological gravo-magnetohydrodynamical "zoom-in" simulations of 40 Milky Way-mass halos and 26 dwarf galaxy-mass halos run with the moving-mesh code Arepo. Auriga adopts the $\Lambda$ Cold Dark Matter ($\Lambda$CDM) cosmogony and includes a comprehensive galaxy formation physics model following the coupled cosmic evolution of dark matter, gas, stars, and supermassive black holes which has been shown to produce numerically well-converged galaxy properties for Milky Way-mass systems. We describe the first public data release of this augmented suite of Auriga simulations, which includes raw snapshots, group catalogues, merger trees, initial conditions, and supplementary data, as well as public analysis tools with worked examples of how to use the data. To demonstrate the value and robustness of the simulation predictions, we analyse a series of low-redshift global properties that compare well with many observed scaling relations, such as the Tully-Fisher relation, the star-forming main sequence, and HI gas fraction/disc thickness. Finally, we show that star-forming gas discs appear to build rotation and velocity dispersion rapidly for $z\gtrsim 3$ before they "settle" into ever-increasing rotation-dispersion ratios ($V/\sigma$). This evolution appears to be in rough agreement with some kinematic measurements from H$\alpha$ observations, and demonstrates an application of how to utilise the released data., Comment: Matches final MNRAS version
- Published
- 2024
18. The thesan project: Connecting ionized bubble sizes to their local environments during the Epoch of Reionization
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Neyer, Meredith, primary, Smith, Aaron, additional, Kannan, Rahul, additional, Vogelsberger, Mark, additional, Garaldi, Enrico, additional, Galárraga-Espinosa, Daniela, additional, Borrow, Josh, additional, Hernquist, Lars, additional, Pakmor, Rüdiger, additional, and Springel, Volker, additional
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- 2024
- Full Text
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19. Magnetic field amplification in cosmological zoom simulations from dwarf galaxies to galaxy groups
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Pakmor, Rüdiger; https://orcid.org/0000-0003-3308-2420, Bieri, Rebekka; https://orcid.org/0000-0002-4554-4488, van de Voort, Freeke, Werhahn, Maria, Fattahi, Azadeh; https://orcid.org/0000-0002-6831-5215, Guillet, Thomas; https://orcid.org/0000-0002-0271-5953, Pfrommer, Christoph; https://orcid.org/0000-0002-7275-3998, Springel, Volker; https://orcid.org/0000-0001-5976-4599, Talbot, Rosie Y; https://orcid.org/0000-0001-9393-7879, Pakmor, Rüdiger; https://orcid.org/0000-0003-3308-2420, Bieri, Rebekka; https://orcid.org/0000-0002-4554-4488, van de Voort, Freeke, Werhahn, Maria, Fattahi, Azadeh; https://orcid.org/0000-0002-6831-5215, Guillet, Thomas; https://orcid.org/0000-0002-0271-5953, Pfrommer, Christoph; https://orcid.org/0000-0002-7275-3998, Springel, Volker; https://orcid.org/0000-0001-5976-4599, and Talbot, Rosie Y; https://orcid.org/0000-0001-9393-7879
- Abstract
Magnetic fields are ubiquitous in the Universe. Recently, cosmological simulations of galaxies have successfully begun to incorporate magnetic fields and their evolution in galaxies and their haloes. However, so far they have mostly focused on Milky Way-like galaxies. Here we analyse a sample of high resolution cosmological zoom simulations of disc galaxies in haloes with mass ${M}_\rm {200c}$ from $10^{10}\, \rm {M}_\odot$ to $10^{13}\, \rm {M}_\odot$, simulated with the Auriga galaxy formation model. We show that with sufficient numerical resolution the magnetic field amplification and saturation is converged. The magnetic field strength reaches equipartition with turbulent energy density for galaxies in haloes with ${M}_\rm {200c}\gtrsim 10^{11.5}\, \mathrm{M_\odot }$. For galaxies in less massive haloes, the magnetic field strength saturates at a fraction of equipartition that decreases with decreasing halo mass. For our lowest mass haloes, the magnetic field saturates significantly below 10 % of equipartition. We quantify the resolution we need to obtain converged magnetic field strengths and discuss our resolution requirements also in the context of the IllustrisTNG cosmological box simulations. We show that, at z = 0, rotation-dominated galaxies in our sample exhibit for the most part an ordered large scale magnetic field, with fewer field reversals in more massive galaxies. Finally, we compare the magnetic fields in our cosmological galaxies at z = 0 with simulations of isolated galaxies in a collapsing halo setup. Our results pave the way for detailed studies of cosmic rays and other physical processes in similar cosmological galaxy simulations that crucially depend on the strength and structure of magnetic fields.
- Published
- 2024
20. Overview and public data release of the Auriga Project: cosmological simulations of dwarf and Milky Way-mass galaxies
- Author
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Grand, Robert J. J., Fragkoudi, Francesca, Gómez, Facundo A., Jenkins, Adrian, Marinacci, Federico, Pakmor, Rüdiger, Springel, Volker, Grand, Robert J. J., Fragkoudi, Francesca, Gómez, Facundo A., Jenkins, Adrian, Marinacci, Federico, Pakmor, Rüdiger, and Springel, Volker
- Abstract
We present an extended suite of the Auriga cosmological gravo-magnetohydrodynamical ``zoom-in'' simulations of 40 Milky Way-mass halos and 26 dwarf galaxy-mass halos run with the moving-mesh code Arepo. Auriga adopts the $\Lambda$ Cold Dark Matter ($\Lambda$CDM) cosmogony and includes a comprehensive galaxy formation physics model following the coupled cosmic evolution of dark matter, gas, stars, and supermassive black holes which has been shown to produce numerically well-converged galaxy properties for Milky Way-mass systems. We describe the first public data release of this augmented suite of Auriga simulations, which includes raw snapshots, group catalogues, merger trees, initial conditions, and supplementary data, as well as public analysis tools with worked examples of how to use the data. To demonstrate the value and robustness of the simulation predictions, we analyse a series of low-redshift global properties that compare well with many observed scaling relations, such as the Tully-Fisher relation, the star-forming main sequence, and HI gas fraction/disc thickness. Finally, we show that star-forming gas discs appear to build rotation and velocity dispersion rapidly for $z\gtrsim 3$ before they ``settle'' into ever-increasing rotation-dispersion ratios ($V/\sigma$). This evolution appears to be in rough agreement with some kinematic measurements from H$\alpha$ observations, and demonstrates an application of how to utilise the released data., Comment: 18 pages. Submitted
- Published
- 2024
21. Supersonic turbulence simulations with GPU-based high-order Discontinuous Galerkin hydrodynamics
- Author
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Cernetic, Miha, Springel, Volker, Guillet, Thomas, Pakmor, Rüdiger, Cernetic, Miha, Springel, Volker, Guillet, Thomas, and Pakmor, Rüdiger
- Abstract
We investigate the numerical performance of a Discontinuous Galerkin (DG) hydrodynamics implementation when applied to the problem of driven, isothermal supersonic turbulence. While the high-order element-based spectral approach of DG is known to efficiently produce accurate results for smooth problems (exponential convergence with expansion order), physical discontinuities in solutions, like shocks, prove challenging and may significantly diminish DG's applicability to practical astrophysical applications. We consider whether DG is able to retain its accuracy and stability for highly supersonic turbulence, characterized by a network of shocks. We find that our new implementation, which regularizes shocks at sub-cell resolution with artificial viscosity, still performs well compared to standard second-order schemes for moderately high Mach number turbulence, provided we also employ an additional projection of the primitive variables onto the polynomial basis to regularize the extrapolated values at cell interfaces. However, the accuracy advantage of DG diminishes significantly in the highly supersonic regime. Nevertheless, in turbulence simulations with a wide dynamic range that start with supersonic Mach numbers and can resolve the sonic point, the low numerical dissipation of DG schemes still proves advantageous in the subsonic regime. Our results thus support the practical applicability of DG schemes for demanding astrophysical problems that involve strong shocks and turbulence, such as star formation in the interstellar medium. We also discuss the substantial computational cost of DG when going to high order, which needs to be weighted against the resulting accuracy gain. For problems containing shocks, this favours the use of comparatively low DG order., Comment: 22 pages, 14 figures, submitted to MNRAS
- Published
- 2024
22. Overview and public data release of the augmented Auriga Project: cosmological simulations of dwarf and Milky Way-mass galaxies.
- Author
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Grand, Robert J J, Fragkoudi, Francesca, Gómez, Facundo A, Jenkins, Adrian, Marinacci, Federico, Pakmor, Rüdiger, and Springel, Volker
- Subjects
DATA release ,GALAXY formation ,DWARF galaxies ,GALAXIES ,SUPERMASSIVE black holes ,DARK matter ,STARS - Abstract
We present an extended suite of the Auriga cosmological gravo-magnetohydrodynamical 'zoom-in' simulations of 40 Milky Way-mass haloes and 26 dwarf galaxy–mass haloes run with the moving-mesh code arepo. Auriga adopts the Lambda cold dark matter cosmogony and includes a comprehensive galaxy formation physics model following the coupled cosmic evolution of dark matter, gas, stars, and supermassive black holes which has been shown to produce numerically well-converged galaxy properties for Milky Way-mass systems. We describe the first public data release of this augmented suite of Auriga simulations, which includes raw snapshots, group catalogues, merger trees, initial conditions, and supplementary data, as well as public analysis tools with worked examples of how to use the data. To demonstrate the value and robustness of the simulation predictions, we analyse a series of low-redshift global properties that compare well with many observed scaling relations, such as the Tully–Fisher relation, the star-forming (SF) main sequence, and H i gas fraction/disc thickness. Finally, we show that SF gas discs appear to build rotation and velocity dispersion rapidly for |$z\gtrsim 3$| before they 'settle' into ever-increasing rotation-dispersion ratios (|$V/\sigma$|). This evolution appears to be in rough agreement with some kinematic measurements from H |$\alpha$| observations, and demonstrates an application of how to utilize the released data. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
23. The thesan project: public data release of radiation-hydrodynamic simulations matching reionization-era JWST observations
- Author
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Garaldi, Enrico, primary, Kannan, Rahul, additional, Smith, Aaron, additional, Borrow, Josh, additional, Vogelsberger, Mark, additional, Pakmor, Rüdiger, additional, Springel, Volker, additional, Hernquist, Lars, additional, Galárraga-Espinosa, Daniela, additional, Yeh, Jessica Y -C, additional, Shen, Xuejian, additional, Xu, Clara, additional, Neyer, Meredith, additional, Spina, Benedetta, additional, Almualla, Mouza, additional, and Zhao, Yu, additional
- Published
- 2024
- Full Text
- View/download PDF
24. The origin of lopsided satellite galaxy distribution around isolated systems in MillenniumTNG
- Author
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Liu, Yikai, primary, Wang, Peng, additional, Guo, Hong, additional, Springel, Volker, additional, Bose, Sownak, additional, Pakmor, Rüdiger, additional, and Hernquist, Lars, additional
- Published
- 2024
- Full Text
- View/download PDF
25. Magnetic field amplification in cosmological zoom simulations from dwarf galaxies to galaxy groups
- Author
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Pakmor, Rüdiger, primary, Bieri, Rebekka, additional, van de Voort, Freeke, additional, Werhahn, Maria, additional, Fattahi, Azadeh, additional, Guillet, Thomas, additional, Pfrommer, Christoph, additional, Springel, Volker, additional, and Talbot, Rosie Y, additional
- Published
- 2024
- Full Text
- View/download PDF
26. The evolutionary path of void galaxies in TNG300 simulation
- Author
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Rodríguez-Medrano, Agustín M, primary, Springel, Volker, additional, Stasyszyn, Federico A, additional, and Paz, Dante J, additional
- Published
- 2024
- Full Text
- View/download PDF
27. Cosmological gas accretion history on to the stellar discs of Milky Way-like galaxies in the Auriga simulations – II. The inside–out growth of discs.
- Author
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Iza, Federico G, Nuza, Sebastián E, Scannapieco, Cecilia, Grand, Robert J J, Gómez, Facundo A, Springel, Volker, Pakmor, Rüdiger, Marinacci, Federico, and Fragkoudi, Francesca
- Subjects
GALAXIES ,STAR formation ,STELLAR populations ,MILKY Way ,GALAXY formation ,ACCRETION (Astrophysics) - Abstract
We investigate the growth of stellar discs in Milky Way-mass galaxies using the magnetohydrodynamical simulations of the Auriga Project in a full cosmological context. We focus on the gas accretion process along the discs, calculating the net, infall and outflow rates as a function of galactocentric distance, and investigate the relation between them and the star formation activity. The stellar distributions of around 70 per cent of the simulated galaxies exhibit an 'inside–out' pattern, with older (younger) stellar populations preferentially located in the inner (outer) disc regions. In all cases, we find a very tight correlation between the infall, outflow, and net accretion rates, as well as between these three quantities and the star formation rate. This is because the amount of gas which is ultimately available for star formation in each radial ring depends not only on the infall rates, but also on the amount of gas leaving the disc in outflows, which directly relates to the local star formation level. Therefore, any of these rates can be used to identify galaxies with inside–out growth. For these galaxies, the correlation between the dominant times of accretion/star formation and disc radius is well fitted by a linear function. We also find that, when averaged over galaxies with formation histories similar to the Milky Way, the simulated accretion rates show a similar evolution (both temporally and radially integrated) to the usual accretion prescriptions used in chemical evolution models, although some major differences arise at early times and in the inner disc regions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
28. General relativistic moving-mesh hydrodynamic simulations with arepo and applications to neutron star mergers.
- Author
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Lioutas, Georgios, Bauswein, Andreas, Soultanis, Theodoros, Pakmor, Rüdiger, Springel, Volker, and Röpke, Friedrich K
- Subjects
STELLAR mergers ,NEUTRON stars ,EINSTEIN field equations ,STELLAR oscillations ,FREQUENCIES of oscillating systems ,GRAVITATIONAL waves ,RELATIVISTIC astrophysics - Abstract
We implement general relativistic hydrodynamics in the moving-mesh code arepo. We also couple a solver for the Einstein field equations employing the conformal flatness approximation. The implementation is validated by evolving isolated static neutron stars using a fixed metric or a dynamical space–time. In both tests, the frequencies of the radial oscillation mode match those of independent calculations. We run the first moving-mesh simulation of a neutron star merger. The simulation includes a scheme to adaptively refine or derefine cells and thereby adjusting the local resolution dynamically. The general dynamics are in agreement with independent smoothed particle hydrodynamics and static-mesh simulations of neutron star mergers. Coarsely comparing, we find that dynamical features like the post-merger double-core structure or the quasi-radial oscillation mode persist on longer time scales, possibly reflecting a low numerical diffusivity of our method. Similarly, the post-merger gravitational wave emission shows the same features as observed in simulations with other codes. In particular, the main frequency of the post-merger phase is found to be in good agreement with independent results for the same binary system, while, in comparison, the amplitude of the post-merger gravitational wave signal falls off slower, i.e. the post-merger oscillations are less damped. The successful implementation of general relativistic hydrodynamics in the moving-mesh arepo code, including a dynamical space–time evolution, provides a fundamentally new tool to simulate general relativistic problems in astrophysics. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
29. The mass accretion history of dark matter haloes down to Earth mass.
- Author
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Liu, Yizhou, Gao, Liang, Bose, Sownak, Frenk, Carlos S, Jenkins, Adrian, Springel, Volker, Wang, Jie, White, Simon D M, and Zheng, Haonan
- Subjects
DARK matter ,GALAXY formation ,WEAKLY interacting massive particles ,DARK energy - Abstract
We take advantage of the unprecedented dynamical range provided by the 'Cosmic-Zoom' project to study the mass accretion history (MAH) of present-day dark matter haloes over the entire mass range present in the Lambda cold dark matter paradigm when the dark matter is made of weakly interacting massive particles of mass 100 GeV. In particular, we complement previous studies by exploring the MAHs of haloes with mass from |$10^8\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$| down to Earth mass, |$10^{-6}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$|. The formation redshift of low-mass haloes anticorrelates weakly with mass, peaking at z = 3 for haloes of mass |$10^{-4}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$|. Even lower masses are affected by the free-streaming cut-off in the primordial spectrum of density fluctuations and form at lower redshift. We compare MAHs in our simulations with predictions from two analytical models based on the extended Press–Schechter theory (EPS), and three empirical models derived by fitting and extrapolating either results from cosmological N -body simulations or Monte Carlo realizations of halo growth. All models fit our simulations reasonably well over the mass range for which they were calibrated. While the empirical models match better for more massive haloes, |$M\gt 10^{10}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$| , the analytical models do better when extrapolated down to Earth mass. At the higher masses, we explore the correlation between local environment density and MAH, finding that biases are relatively weak, with typical MAHs for haloes in extremely low-density and in typical regions differing by less than 20 per cent at high redshift. If this result can be extrapolated to lower halo masses, we conclude that EPS theory predicts the hierarchical build up of dark matter haloes quite well over the entire halo mass range. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. The structure and dynamics of massive high-z cosmic-web filaments: three radial zones in filament cross-sections.
- Author
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Lu, Yue Samuel, Mandelker, Nir, Oh, Siang Peng, Dekel, Avishai, van den Bosch, Frank C, Springel, Volker, Nagai, Daisuke, and van de Voort, Freeke
- Subjects
GALAXY formation ,FIBERS ,CENTRIFUGAL force ,LARGE scale structure (Astronomy) ,GALACTIC halos ,SHEARING force ,POTENTIAL well - Abstract
We analyse the internal structure and dynamics of cosmic-web filaments connecting massive high- z haloes. Our analysis is based on a high-resolution arepo cosmological simulation zooming-in on three Mpc-scale filaments feeding three massive haloes of |$\sim 10^{12}\, \text{M}_\odot$| at z ∼ 4, embedded in a large-scale sheet. Each filament is surrounded by a cylindrical accretion shock of radius |$r_{\rm shock} \sim 50 \, {\rm kpc}$|. The post-shock gas is in virial equilibrium within the potential well set by an isothermal dark-matter filament. The filament line-mass is |$\sim 9\times 10^8\, \text{M}_\odot \, {\rm kpc}^{-1}$| , the gas fraction within r
shock is the universal baryon fraction, and the virial temperature is ∼7 × 105 K. These all match expectations from analytical models for filament properties as a function of halo mass and redshift. The filament cross-section has three radial zones. In the outer 'thermal' (T) zone, |$r \ge 0.65 \, r_{\rm shock}$| , inward gravity, and ram-pressure forces are overbalanced by outward thermal pressure forces, decelerating the inflowing gas and expanding the shock outwards. In the intermediate 'vortex' (V) zone, 0.25 ≤ r / rshock ≤ 0.65, the velocity field is dominated by a quadrupolar vortex structure due to offset inflow along the sheet through the post-shock gas. The outward force is dominated by centrifugal forces associated with these vortices, with additional contributions from global rotation and thermal pressure. Shear and turbulent forces associated with the vortices act inwards. The inner 'stream' (S) zone, |$r \lt 0.25 \, r_{\rm shock}$| , is a dense isothermal core, |$T\sim 3 \times 10^4 \, {\rm K}$| and |$n_{\rm H}\sim 0.01 \, {\rm cm^{-3}}$| , defining the cold streams that feed galaxies. The core is formed by an isobaric cooling flow and is associated with a decrease in outward forces, though exhibiting both inflows and outflows. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
31. Spectrally resolved cosmic rays - III. Dynamical impact and properties of the circumgalactic medium.
- Author
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Girichidis, Philipp, Werhahn, Maria, Pfrommer, Christoph, Pakmor, Rüdiger, and Springel, Volker
- Subjects
GALACTIC evolution ,DWARF galaxies ,STAR formation ,COSMIC rays ,GALAXY formation ,DIFFUSION coefficients ,GALAXIES - Abstract
Cosmic rays (CRs) are dynamically important in the evolution of galaxies by regulating star formation and powering galactic outflows. However, to what extent CRs regulate galaxy formation depends on the coupling strength of CRs with the ambient plasma and the effective CR transport speed. Moreover, both properties sensitively depend on the CR momentum, which is largely unexplored in three-dimensional hydrodynamical simulations. We perform magnetohydrodynamical simulations of entire galaxies with masses ranging from 10
10 to |$10^{12}\, \mathrm{M}_\odot$| and compare dynamically coupled CRs in the grey approximation with a spectrally resolved model that includes CR momenta from |$0.1\, \mathrm{GeV} c^{-1}$| to |$100\, \mathrm{TeV} c^{-1}$|. We find that hadronic cooling of CRs dominates over Alfvén cooling, with the latter emulating CR losses as a result of streaming of CRs down their pressure gradient. While star formation rates and galaxy morphologies are only mildly affected by the spectral CR modelling, mass loading factors of galactic outflows can differ by up to a factor of 4 in dwarf galaxies. All simulated low-mass haloes (M = 1010 , 1011 , and |$3\times 10^{11}\, \mathrm{M}_\odot$|) drive strong outflows, where CR transport is temporally dominated by advection. In contrast, the Milky Way-mass galaxy with |$M=10^{12}\, \mathrm{M}_\odot$| does not drive sustained outflows, so that CR transport is entirely dominated by diffusion. The effective energy weighted diffusion coefficients vary by two orders of magnitude from the canonical energy-weighted values of |$\langle {D}\rangle _{e_\mathrm{cr}}\sim 10^{28}\, \mathrm{cm^2\, s^{-1}}$| in the disc up to |$3\times 10^{29}\, \mathrm{cm^2\, s^{-1}}$| in the circumgalactic medium, where we observe substantial temperature and CR pressure differences between our grey and spectral CR models. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
32. Non-ideal magnetohydrodynamics on a moving mesh II: Hall effect.
- Author
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Zier, Oliver, Mayer, Alexander C, and Springel, Volker
- Subjects
HALL effect ,MAGNETOHYDRODYNAMICS ,MAGNETIC fields ,DISPERSION relations ,DIFFUSION coefficients - Abstract
In this work, we extend the non-ideal magnetohydrodynamics (MHD) solver in the moving-mesh code arepo to include the Hall effect. The core of our algorithm is based on an estimation of the magnetic field gradients by a least-squares reconstruction on the unstructured mesh, which we also used in the companion paper for Ohmic and ambipolar diffusion. In an extensive study of simulations of a magnetic shock, we show that without additional magnetic diffusion our algorithm for the Hall effect becomes unstable at high resolution. We can however stabilize it by artificially increasing the Ohmic resistivity, η
OR , so that it satisfies the condition ηOR ≥ ηH /5, where ηH is the Hall diffusion coefficient. Adopting this solution, we find second-order convergence for the C-shock and are also able to accurately reproduce the dispersion relation of the whistler waves. As a first application of the new scheme, we simulate the collapse of a magnetized cloud with constant Hall parameter ηH and show that, depending on the sign of ηH , the magnetic braking can either be weakened or strengthened by the Hall effect. The quasi-Lagrangian nature of the moving-mesh method used here automatically increases the resolution in the forming core, making it well suited for more realistic studies with non-constant magnetic diffusivities in the future. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
33. Close encounters of star–black hole binaries with single stars.
- Author
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Ryu, Taeho, de Mink, Selma E, Farmer, Rob, Pakmor, Rüdiger, Perna, Rosalba, and Springel, Volker
- Subjects
MAIN sequence (Astronomy) ,STAR clusters ,STELLAR collisions ,STELLAR evolution ,STELLAR mass ,BINARY stars ,ASTROPHYSICAL collisions - Abstract
Multibody dynamical interactions of binaries with other objects are one of the main driving mechanisms for the evolution of star clusters. It is thus important to bring our understanding of three-body interactions beyond the commonly employed point-particle approximation. To this end, we here investigate the hydrodynamics of three-body encounters between star–black hole (BH) binaries and single stars, focusing on the identification of final outcomes and their long-term evolution and observational properties, using the moving-mesh hydrodynamics code AREPO. This type of encounter produces five types of outcomes: stellar disruption, stellar collision, weak perturbation of the original binary, binary member exchange, and triple formation. The two decisive parameters are the binary phase angle, which determines which two objects meet at the first closest approach, and the impact parameter, which sets the boundary between violent and non-violent interactions. When the impact parameter is smaller than the semimajor axis of the binary, tidal disruptions and star-BH collisions frequently occur when the BH and the incoming star first meet, while the two stars mostly merge when the two stars meet first instead. In both cases, the BHs accrete from an accretion disc at super-Eddington rates, possibly generating flares luminous enough to be observed. The stellar collision products either form a binary with the BH or remain unbound to the BH. Upon collision, the merged stars are hotter and larger than the main sequence stars of the same mass at similar age. Even after recovering their thermal equilibrium state, stellar collision products, if isolated, would remain hotter and brighter than main sequence stars until becoming giants. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
34. Non-ideal magnetohydrodynamics on a moving mesh I: ohmic and ambipolar diffusion.
- Author
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Zier, Oliver, Springel, Volker, and Mayer, Alexander C
- Subjects
- *
MAGNETOHYDRODYNAMICS , *HALL effect , *MAGNETIC structure , *PLASMA Alfven waves ,COLD regions - Abstract
Especially in cold and high-density regions, the assumptions of ideal magnetohydrodynamics (MHD) can break down, making first order non-ideal terms such as ohmic and ambipolar diffusion as well as the Hall effect important. In this study, we present a new numerical scheme for the first two resistive terms, which we implement in the moving-mesh code arepo using the single-fluid approximation combined with a new gradient estimation technique based on a least-squares fit per interface. Through various test calculations including the diffusion of a magnetic peak, the structure of a magnetic C-shock, and the damping of an Alfvén wave, we show that we can achieve an accuracy comparable to the state-of-the-art code athena++ . We apply the scheme to the linear growth of the magnetorotational instability and find good agreement with the analytical growth rates. By simulating the collapse of a magnetized cloud with constant magnetic diffusion, we show that the new scheme is stable even for large contrasts in the spatial resolution. Thanks to the Lagrangian nature of the moving mesh method the new scheme is thus well suited for intended future applications where a high resolution in the dense cores of collapsing protostellar clouds needs to be achieved. In a forthcoming work, we will extend the scheme to include the Hall effect. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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