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Category: galaxy formation and evolution (Page 2 of 3)

Martizzi et al. (2019)

Baryons in the Cosmic Web of IllustrisTNG – I: gas in knots, filaments, sheets, and voids

by
Martizzi, Davide; Vogelsberger, Mark; Artale, Maria Celeste; Haider, Markus; Torrey, Paul; Marinacci, Federico; Nelson, Dylan; Pillepich, Annalisa; Weinberger, Rainer; Hernquist, Lars; Naiman, Jill; Springel, Volker

abstract
We analyse the IllustrisTNG simulations to study the mass, volume fraction, and phase distribution of gaseous baryons embedded in the knots, filaments, sheets, and voids of the Cosmic Web from redshift z = 8 to redshift z = 0. We find that filaments host more star-forming gas than knots, and that filaments also have a higher relative mass fraction of gas in this phase than knots. We also show that the cool, diffuse intergalactic medium [IGM; T< 10^5 K, n_H< 10^{-4}(1+z) cm^{-3}] and the warm-hot intergalactic medium [WHIM; 10^5 < T< 10^7 K, n_H < 10^{-4}(1+z) cm^{-3}] constitute {̃ } 39 and {̃ } 46{{ per cent}} of the baryons at redshift z = 0, respectively. Our results indicate that the WHIM may constitute the largest reservoir of missing baryons at redshift z = 0. Using our Cosmic Web classification, we predict the WHIM to be the dominant baryon mass contribution in filaments and knots at redshift z = 0, but not in sheets and voids where the cool, diffuse IGM dominates. We also characterize the evolution of WHIM and IGM from redshift z = 4 to redshift z = 0, and find that the mass fraction of WHIM in filaments and knots evolves only by a factor of ̃2 from redshift z = 0 to 1, but declines faster at higher redshift. The WHIM only occupies 4-11 per cent of the volume at redshift 0 ≤ z ≤ 1. We predict the existence of a significant number of currently undetected O VII and Ne IX absorption systems in cosmic filaments, which could be detected by future X-ray telescopes like Athena.

published in
Monthly Notices of the Royal Astronomical Society, Volume 486, Issue 3, p.3766-3787, July 2019

links to paper
[ADS][arXiv]

Nelson et al. (2019)

The IllustrisTNG simulations: public data release

by
Nelson, Dylan; Springel, Volker; Pillepich, Annalisa; Rodriguez-Gomez, Vicente; Torrey, Paul; Genel, Shy; Vogelsberger, Mark; Pakmor, Ruediger; Marinacci, Federico; Weinberger, Rainer; Kelley, Luke; Lovell, Mark; Diemer, Benedikt; Hernquist, Lars

abstract
We present the full public release of all data from the TNG100 and TNG300 simulations of the IllustrisTNG project. IllustrisTNG is a suite of large volume, cosmological, gravo-magnetohydrodynamical simulations run with the moving-mesh code Arepo. TNG includes a comprehensive model for galaxy formation physics, and each TNG simulation self-consistently solves for the coupled evolution of dark matter, cosmic gas, luminous stars, and supermassive black holes from early time to the present day, z=0. Each of the flagship runs—TNG50, TNG100, and TNG300—are accompanied by halo/subhalo catalogs, merger trees, lower-resolution and dark-matter only counterparts, all available with 100 snapshots. We discuss scientific and numerical cautions and caveats relevant when using TNG. The data volume now directly accessible online is ̃750 TB, including 1200 full volume snapshots and ̃80,000 high time-resolution subbox snapshots. This will increase to ̃1.1 PB with the future release of TNG50. Data access and analysis examples are available in IDL, Python, and Matlab. We describe improvements and new functionality in the web-based API, including on-demand visualization and analysis of galaxies and halos, exploratory plotting of scaling relations and other relationships between galactic and halo properties, and a new JupyterLab interface. This provides an online, browser-based, near-native data analysis platform enabling user computation with local access to TNG data, alleviating the need to download large datasets.

published in
Computational Astrophysics and Cosmology, Volume 6, Issue 1, article id. 2, 29 pp., May 2019

links to paper
[ADS][arXiv]

Torrey et al. (2019)

The evolution of the mass-metallicity relation and its scatter in IllustrisTNG

by
Torrey, Paul; Vogelsberger, Mark; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Nelson, Dylan; Naiman, Jill; Pillepich, Annalisa; Genel, Shy; Weinberger, Rainer; Hernquist, Lars

abstract
The coevolution of galaxies and their metal content serves as an important test for galaxy feedback models. We analyse the distribution and evolution of metals within the IllustrisTNG simulation suite with a focus on the gas-phase mass-metallicity relation (MZR). We find that the IllustrisTNG model broadly reproduces the slope and normalization evolution of the MZR across the redshift range 0 < z < 2 and mass range 109 < M*/M < 1010.5. We make predictions for the high-redshift (2 < z < 10) metal content of galaxies which is described by a gradual decline in the normalization of the metallicity with an average high-redshift (z > 2) evolution fit by d log(Z)/dz ≈ -0.064. Our simulations indicate that the metal retention efficiency of the interstellar medium (ISM) is low: a majority of gas-phase metals (̃85 per cent at z = 0) live outside of the ISM, either in an extended gas disc, the circumgalactic medium, or outside the halo. Nevertheless, the redshift evolution in the simulated MZR normalization is driven by the higher gas fractions of high-redshift galaxies, not by changes to the metal retention efficiency. The scatter in the simulated MZR contains a clear correlation with the gas-mass or star formation rate of the system, in agreement with the observed fundamental metallicity relation. The scatter in the MZR is driven by a competition between periods of enrichment- and accretion-dominated metallicity evolution. We expect that while the normalization of the MZR declines with redshift, the slope of the correlation between metallicity and gas-mass at fixed stellar mass is not a strong function of redshift. Our results indicate that the gas fraction dependence of `regulator’ style models allows them to simultaneously explaining the shape, redshift evolution, and existence of correlated scatter with gas fraction about the MZR.

published in
Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 4, p.5587-5607, April 2019

links to paper
[ADS][arXiv]

Rodriguez-Gomez et al. (2019)

The optical morphologies of galaxies in the IllustrisTNG simulation: a comparison to Pan-STARRS observations

by
Rodriguez-Gomez, Vicente; Snyder, Gregory F.; Lotz, Jennifer M.; Nelson, Dylan; Pillepich, Annalisa; Springel, Volker; Genel, Shy; Weinberger, Rainer; Tacchella, Sandro; Pakmor, Rüdiger; Torrey, Paul; Marinacci, Federico; Vogelsberger, Mark; Hernquist, Lars; Thilker, David A.

abstract
We have generated synthetic images of ̃27 000 galaxies from the IllustrisTNG and the original Illustris hydrodynamic cosmological simulations, designed to match Pan-STARRS observations of log10(M*/M) ≈ 9.8-11.3 galaxies at z ≈ 0.05. Most of our synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering, and performing the radiative transfer directly on the Voronoi mesh used by the simulations themselves. We have analysed both our synthetic and real Pan-STARRS images with the newly developed statmorph code, which calculates non-parametric morphological diagnostics – including the Gini-M20and concentration-asymmetry-smoothness statistics – and performs 2D Sérsic fits. Overall, we find that the optical morphologies of IllustrisTNG galaxies are in good agreement with observations, and represent a substantial improvement compared to the original Illustris simulation. In particular, the locus of the Gini-M20 diagram is consistent with that inferred from observations, while the median trends with stellar mass of all the morphological, size and shape parameters considered in this work lie within the ̃1σ scatter of the observational trends. However, the IllustrisTNG model has some difficulty with more stringent tests, such as producing a strong morphology-colour relation. This results in a somewhat higher fraction of red discs and blue spheroids compared to observations. Similarly, the morphology-size relation is problematic: while observations show that discs tend to be larger than spheroids at a fixed stellar mass, such a trend is not present in IllustrisTNG.

published in
Monthly Notices of the Royal Astronomical Society, Volume 483, Issue 3, p.4140-4159, March 2019

links to paper
[ADS][arXiv]

Yun et al. (2019)

Jellyfish galaxies with the IllustrisTNG simulations – I. Gas-stripping phenomena in the full cosmological context

by
Yun, Kiyun; Pillepich, Annalisa; Zinger, Elad; Nelson, Dylan; Donnari, Martina; Joshi, Gandhali; Rodriguez-Gomez, Vicente; Genel, Shy; Weinberger, Rainer; Vogelsberger, Mark; Hernquist, Lars

abstract
We use the IllustrisTNG simulations to study the demographics and properties of jellyfish galaxies in the full cosmological context. By jellyfish galaxies, we mean satellites orbiting in massive groups and clusters that exhibit highly asymmetric distributions of gas and gas tails. In particular, we select TNG100 galaxies at low redshifts (z ≤ 0.6) with stellar mass exceeding 10^{9.5} M_{☉} and with host halo masses in the range 10^{13} ≤ M_200c/ M_{☉}≤ 10^{14.6}. Among more than about 6000 (2600) galaxies with stars (and some gas), we identify 800 jellyfish galaxies by visually inspecting their gas and stellar mass maps in random projections. Namely, about 31 per cent of cluster satellites are found with signatures of ram-pressure stripping and gaseous tails stemming from their main luminous bodies. This is a lower limit: the random orientation entails a loss of about 30 per cent of galaxies that in an optimal projection would otherwise be identified as jellyfish. Furthermore, jellyfish galaxies are more frequent at intermediate and large cluster-centric distances (r/R200c ≳ 0.25), in more massive hosts and at smaller satellite masses, and they typically orbit supersonically. The gaseous tails usually extend in opposite directions to the galaxy trajectory, with no relation between tail orientation and position of the host’s centre. Finally, jellyfish galaxies are late infallers (<2.5-3 Gyr ago, at z = 0) and the emergence of gaseous tails correlates well with the presence of bow shocks in the intracluster medium.

published in
Monthly Notices of the Royal Astronomical Society, Volume 483, Issue 1, p.1042-1066, February 2019

links to paper
[ADS][arXiv]

Genel et al. (2019)

A Quantification of the Butterfly Effect in Cosmological Simulations and Implications for Galaxy Scaling Relations

by
Genel, Shy; Bryan, Greg L.; Springel, Volker; Hernquist, Lars; Nelson, Dylan; Pillepich, Annalisa; Weinberger, Rainer; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark

abstract
We study the chaotic-like behavior of cosmological simulations by quantifying how minute perturbations grow over time and manifest as macroscopic differences in galaxy properties. When we run pairs of “shadow” simulations that are identical except for random minute initial displacements to particle positions (e.g., of order {10}-7 {pc}), the results diverge from each other at the individual galaxy level (while the statistical properties of the ensemble of galaxies are unchanged). After cosmological times, the global properties of pairs of “shadow” galaxies that are matched between the simulations differ from each other, generally at a level of ̃2-25%, depending on the considered physical quantity. We perform these experiments using cosmological volumes of {(25{–}50{Mpc}/h)}3evolved either purely with dark matter, or with baryons and star formation but no feedback, or else using the full feedback model of the IllustrisTNG project. The runs cover four resolution levels spanning a factor of 512 in mass. We find that, without feedback, the differences between shadow galaxies generally become smaller as the resolution increases—but with the IllustrisTNG model, the results mostly converge toward a “floor.” This hints at the role of feedback in setting the chaotic properties of galaxy formation. Importantly, we compare the macroscopic differences between shadow galaxies to the overall scatter in various galaxy scaling relations, and conclude that, for the star formation-mass and the Tully-Fisher relations, the butterfly effect in our simulations contributes significantly to the overall scatter. We find that our results are robust to whether random numbers are used in the subgrid models or not. We discuss the implications for galaxy formation theory in general and for cosmological simulations in particular.

 published in
The Astrophysical Journal, Volume 871, Issue 1, article id. 21, 27 pp. (January 2019)

links to paper
[ADS][arXiv]

Lovell et al. (2018)

The fraction of dark matter within galaxies from the IllustrisTNG simulations

by
Lovell, Mark R.; Pillepich, Annalisa; Genel, Shy; Nelson, Dylan; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Weinberger, Rainer; Torrey, Paul; Vogelsberger, Mark; Alabi, Adebusola; Hernquist, Lars

abstract
We use the IllustrisTNG (TNG) cosmological simulations to provide theoretical expectations for the dark matter mass fractions (DMFs) and circular velocity profiles of galaxies. TNG predicts flat circular velocity curves for z = 0 Milky Way (MW)-like galaxies beyond a few kpc from the galaxy centre, in better agreement with observational constraints than its predecessor, Illustris. TNG also predicts an enhancement of the dark matter mass within the 3D stellar half-mass radius (r_half; M_200c = 10^{10}-10^{13} M_{☉ }, z ≤ 2) compared to its dark matter only and Illustris counterparts. This enhancement leads TNG present-day galaxies to be dominated by dark matter within their inner regions, with f_DM(< r_half)≳ 0.5 at all masses and with a minimum for MW-mass galaxies. The 1σ scatter is ≲10 per cent at all apertures, which is smaller than that inferred by some observational data sets, e.g. 40 per cent from the SLUGGS survey. TNG agrees with the majority of the observationally inferred values for elliptical galaxies once a consistent initial mass function is adopted (Chabrier) and the DMFs are measured within the same apertures. The DMFs measured within r_half increase towards lower redshifts: this evolution is dominated by the increase in galaxy size with time. At z ̃ 2, the DMF in disc-like TNG galaxies decreases with increasing galaxy mass, with f_DM(< r_half) ̃ 0.10-0.65 for 1010 ≲ Mstars/M ≲ 1012, and are two times higher than if TNG galaxies resided in Navarro-Frenk-White dark matter haloes unaffected by baryonic physics. It remains to be properly assessed whether recent observational estimates of the DMFs at z ̃ 2 rule out the contraction of the dark matter haloes predicted by the TNG model.

published in
Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 2, p.1950-1975, December 2018

links to paper
[ADS][arXiv]

Villaescusa-Navarro et al. (2018)

Ingredients for 21 cm Intensity Mapping

by
Villaescusa-Navarro, Francisco; Genel, Shy; Castorina, Emanuele; Obuljen, Andrej; Spergel, David N.; Hernquist, Lars; Nelson, Dylan; Carucci, Isabella P.; Pillepich, Annalisa; Marinacci, Federico; Diemer, Benedikt; Vogelsberger, Mark; Weinberger, Rainer; Pakmor, Rüdiger

author
Current and upcoming radio telescopes will map the spatial distribution of cosmic neutral hydrogen (H I) through its 21 cm emission. In order to extract the maximum information from these surveys, accurate theoretical predictions are needed. We study the abundance and clustering properties of H I at redshifts z ≤ 5 using TNG100, a large state-of-the-art magnetohydrodynamic simulation of a 75 h -1Mpc box size, which is part of the IllustrisTNG Project. We show that most of the H I lies within dark matter halos, and we provide fits for the halo H I mass function, i.e., the mean H I mass hosted by a halo of mass M at redshift z. We find that only halos with circular velocities larger than ≃30 km s-1contain H I. While the density profiles of H I exhibit a large halo-to-halo scatter, the mean profiles are universal across mass and redshift. The H I in low-mass halos is mostly located in the central galaxy, while in massive halos the H I is concentrated in the satellites. Our simulation reproduces the bias value of damped Lyα systems from observations. We show that the H I and matter density probability distribution functions differ significantly. Our results point out that for small halos, the H I bulk velocity goes in the same direction and has the same magnitude as the halo peculiar velocity, while in large halos, differences show up. We find that halo H I velocity dispersion follows a power law with halo mass. We find a complicated H I bias, with H I already becoming nonlinear at k = 0.3 h Mpc-1 at z ≳ 3. The clustering of H I can, however, be accurately reproduced by perturbative methods. We find a new secondary bias by showing that the clustering of halos depends not only on mass but also on H I content. We compute the amplitude of the H I shot noise and find that it is small at all redshifts, verifying the robustness of BAO measurements with 21 cm intensity mapping. We study the clustering of H I in redshift space and show that linear theory can explain the ratio between the monopoles in redshift and real space down to 0.3, 0.5, and 1 h Mpc-1 at redshifts 3, 4, and 5, respectively. We find that the amplitude of the Fingers-of-God effect is larger for H I than for matter, since H I is found only in halos above a certain mass. We point out that 21 cm maps can be created from N-body simulations rather than full hydrodynamic simulations. Modeling the one-halo term is crucial for achieving percent accuracy with respect to a full hydrodynamic treatment. Although our results are not converged against resolution, they are, however, very useful as we work at the resolution where the model parameters have been calibrated to reproduce galaxy properties.

published in
The Astrophysical Journal, Volume 866, Issue 2, article id. 135, 41 pp. (October 2018).

links to paper
[ADS][arXiv]

Zhu et al. (2018)

Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion

by
Zhu, Qirong; Xu, Dandan; Gaspari, Massimo; Rodriguez-Gomez, Vicente; Nelson, Dylan; Vogelsberger, Mark; Torrey, Paul; Pillepich, Annalisa; Zjupa, Jolanta; Weinberger, Rainer; Marinacci, Federico; Pakmor, Rüdiger; Genel, Shy; Li, Yuexing; Springel, Volker; Hernquist, Lars

abstract
The galaxy Malin 1 contains the largest stellar disc known but the formation mechanism of this structure has been elusive. In this paper, we report a Malin 1 analogue in the 100 Mpc IllustrisTNG simulation and describe its formation history. At redshift zero, this massive galaxy, having a maximum circular velocity Vmax of 430 km s-1, contains a 100 kpc gas/stellar disc with morphology similar to Malin 1. The simulated galaxy reproduces well many observed features of Malin 1’s vast disc, including its stellar ages, metallicities, and gas rotation curve. We trace the extended disc back in time and find that a large fraction of the cold gas at redshift zero originated from the cooling of hot halo gas, triggered by the merger of a pair of intruding galaxies. Our finding provides a novel way to form large galaxy discs as extreme as Malin 1 within the current galaxy formation framework.

published in
Monthly Notices of the Royal Astronomical Society: Letters, Volume 480, Issue 1, p.L18-L22, October 2018

links to paper
[ADS][arXiv]

Weinberger et al. (2018)

Supermassive black holes and their feedback effects in the IllustrisTNG simulation

by
Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Marinacci, Federico; Naiman, Jill; Torrey, Paul; Hernquist, Lars

abstract
We study the population of supermassive black holes (SMBHs) and their effects on massive central galaxies in the IllustrisTNG cosmological hydrodynamical simulations of galaxy formation. The employed model for SMBH growth and feedback assumes a two-mode scenario in which the feedback from active galactic nuclei occurs through a kinetic, comparatively efficient mode at low accretion rates relative to the Eddington limit, and in the form of a thermal, less efficient mode at high accretion rates. We show that the quenching of massive central galaxies happens coincidently with kinetic-mode feedback, consistent with the notion that active supermassive black holes cause the low specific star formation rates observed in massive galaxies. However, major galaxy mergers are not responsible for initiating most of the quenching events in our model. Up to black hole masses of about 10^{8.5} M_{☉}, the dominant growth channel for SMBHs is in the thermal mode. Higher mass black holes stay mainly in the kinetic mode and gas accretion is self-regulated via their feedback, which causes their Eddington ratios to drop, with SMBH mergers becoming the main channel for residual mass growth. As a consequence, the quasar luminosity function is dominated by rapidly accreting, moderately massive black holes in the thermal mode. We show that the associated growth history of SMBHs produces a low-redshift quasar luminosity function and a redshift zero black hole mass – stellar bulge mass relation is in good agreement with observations, whereas the simulation tends to overpredict the high-redshift quasar luminosity function.

published in
Monthly Notices of the Royal Astronomical Society, Volume 479, Issue 3, p.4056-4072, September 2018

links to paper
[ADS][arXiv]

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