Astrophysicist

Author: Rainer Weinberger (Page 2 of 5)

Pillepich et al. (2019)

First results from the TNG50 simulation: the evolution of stellar and gaseous discs across cosmic time

by
Pillepich, Annalisa; Nelson, Dylan; Springel, Volker; Pakmor, Rüdiger; Torrey, Paul; Weinberger, Rainer; Vogelsberger, Mark; Marinacci, Federico; Genel, Shy; van der Wel, Arjen; Hernquist, Lars

abstract
We present a new cosmological, magnetohydrodynamical simulation for galaxy formation: TNG50, the third and final instalment of the IllustrisTNG project. TNG50 evolves 2 × 21603 dark matter particles and gas cells in a volume 50 comoving Mpc across. It hence reaches a numerical resolution typical of zoom-in simulations, with a baryonic element mass of 8.5× 10^4 M_{\odot } and an average cell size of 70-140 pc in the star-forming regions of galaxies. Simultaneously, TNG50 samples ∼700 (6500) galaxies with stellar masses above 10^{10} (10^8) M_{\odot } at z = 1. Here we investigate the structural and kinematical evolution of star-forming galaxies across cosmic time (0 ≲ z ≲ 6). We quantify their sizes, disc heights, 3D shapes, and degree of rotational versus dispersion-supported motions as traced by rest-frame V-band light (i.e. roughly stellar mass) and by H α light (i.e. star-forming and dense gas). The unprecedented resolution of TNG50 enables us to model galaxies with sub-kpc half-light radii and with ≲300-pc disc heights. Coupled with the large-volume statistics, we characterize a diverse, redshift- and mass-dependent structural and kinematical morphological mix of galaxies all the way to early epochs. Our model predicts that for star-forming galaxies the fraction of disc-like morphologies, based on 3D stellar shapes, increases with both cosmic time and galaxy stellar mass. Gas kinematics reveal that the vast majority of 10^{9-11.5} M_{\odot } star-forming galaxies are rotationally supported discs for most cosmic epochs (Vrot/σ > 2-3, z ≲ 5), being dynamically hotter at earlier epochs (z ≳ 1.5). Despite large velocity dispersion at high redshift, cold and dense gas in galaxies predominantly arranges in disky or elongated shapes at all times and masses; these gaseous components exhibit rotationally dominated motions far exceeding the collisionless stellar bodies.

published in
Monthly Notices of the Royal Astronomical Society, Volume 490, Issue 3, p.3196-3233, December 2019

links to paper
[ADS][arXiv]

Xu et al. (2019)

A study of stellar orbit fractions: simulated IllustrisTNG galaxies compared to CALIFA observations

by
Xu, Dandan; Zhu, Ling; Grand, Robert; Springel, Volker; Mao, Shude; van de Ven, Glenn; Lu, Shengdong; Wang, Yougang; Pillepich, Annalisa; Genel, Shy; Nelson, Dylan; Rodriguez-Gomez, Vicente; Pakmor, Rüdiger; Weinberger, Rainer; Marinacci, Federico; Vogelsberger, Mark; Torrey, Paul; Naiman, Jill; Hernquist, Lars

abstract
Motivated by the recently discovered kinematic `Hubble sequence’ shown by the stellar orbit-circularity distribution of 260 CALIFA galaxies, we make use of a comparable galaxy sample at z = 0 with a stellar mass range of M_{*}/M_{\odot }\in [10^{9.7}, 10^{11.4}] selected from the IllustrisTNG simulation and study their stellar orbit compositions in relation to a number of other fundamental galaxy properties. We find that the TNG100 simulation broadly reproduces the observed fractions of different orbital components and their stellar mass dependences. In particular, the mean mass dependences of the luminosity fractions for the kinematically warm and hot orbits are well reproduced within model uncertainties of the observed galaxies. The simulation also largely reproduces the observed peak and trough features at M_{*}≈ 1{-}2× 10^{10} M_{\odot } in the mean distributions of the cold- and hot-orbit fractions, respectively, indicating fewer cooler orbits and more hotter orbits in both more- and less-massive galaxies beyond such a mass range. Several marginal disagreements are seen between the simulation and observations: the average cold-orbit (counter-rotating) fractions of the simulated galaxies below (above) M_{*}≈ 6× 10^{10} M_{\odot } are systematically higher than the observational data by ≲ 10{{ per cent}} (absolute orbital fraction); the simulation also seems to produce more scatter for the cold-orbit fraction and less so for the non-cold orbits at any given galaxy mass. Possible causes that stem from the adopted heating mechanisms are discussed.

published in
Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 1, p.842-854, October 2019

links
[ADS][arXiv]

Barnes et al. (2019)

Enhancing AGN efficiency and cool-core formation with anisotropic thermal conduction

by
Barnes, David J.; Kannan, Rahul; Vogelsberger, Mark; Pfrommer, Christoph; Puchwein, Ewald; Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan;Marinacci, Federico; Pillepich, Annalisa; Torrey, Paul; Hernquist, Lars

abstract
Understanding how baryonic processes shape the intracluster medium (ICM) is of critical importance to the next generation of galaxy cluster surveys. However, many models of structure formation neglect potentially important physical processes, like anisotropic thermal conduction (ATC). We explore the impact of ATC on the prevalence of cool-cores (CCs) via 12 pairs of magnetohydrodynamical galaxy cluster simulations, using the IllustrisTNG model with and without ATC. Examining their properties we find that the addition of ATC has a negligible impact on the median rotation measure, plasma β, the magnetic field-radial direction angle, and the effective Spitzer value. However, the scatter in the angle and effective Spitzer value is 50 per cent larger with ATC because the magnetic field aligns with the azimuthal direction to a greater extent in relaxed clusters. ATC’s impact varies from cluster to cluster and with CC criterion, but its inclusion produces a systematic shift to larger CC fractions at z = 0 for all CC criteria considered. Additionally, the inclusion of ATC flattens the CC fraction redshift evolution, helping to ease the tension with the observed evolution. With ATC, the energy required for the central black hole to self-regulate is reduced by 24 per cent and the gas fraction at 0.01 r_{500} increases by 100 per cent, producing larger CC fractions. ATC makes the ICM unstable to perturbations and the increased efficiency of AGN feedback suggests that its inclusion results in a greater level of mixing in the ICM, demonstrated by the 10 per cent reduction in central metallicity for clusters with ATC.

published in

Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 3, p.3003-3013, September 2019

links to paper
[ADS][arXiv]

Donnari et al. (2019)

The star formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics

by
Donnari, Martina; Pillepich, Annalisa; Nelson, Dylan; Vogelsberger, Mark; Genel, Shy; Weinberger, Rainer; Marinacci, Federico; Springel, Volker; Hernquist, Lars

abstract
We select galaxies from the IllustrisTNG hydrodynamical simulations (M_stars> 10^9 M_☉ at 0 ≤ z ≤ 2) and characterize the shapes and evolutions of their UVJ and star formation rate-stellar mass (SFR-Mstars) diagrams. We quantify the systematic uncertainties related to different criteria to classify star-forming versus quiescent galaxies, different SFR estimates, and by accounting for the star formation measured within different physical apertures. The TNG model returns the observed features of the UVJ diagram at z ≤ 2, with a clear separation between two classes of galaxies. It also returns a tight star-forming main sequence (MS) for M_stars< 10^{10.5} (M_☉) with a ̃0.3 dex scatter at z ̃ 0 in our fiducial choices. If a UVJ-based cut is adopted, the TNG MS exhibits a downwardly bending at stellar masses of about 1010.5-10.7 M. Moreover, the model predicts that {̃ }80 (50) per cent of 1010.5-11 Mgalaxies at z = 0 (z = 2) are quiescent and the numbers of quenched galaxies at intermediate redshifts and high masses are in better agreement with observational estimates than previous models. However, shorter SFR-averaging time-scales imply higher normalizations and scatter of the MS, while smaller apertures lead to underestimating the galaxy SFRs: overall we estimate the inspected systematic uncertainties to sum up to about 0.2-0.3 dex in the locus of the MS and to about 15 percentage points in the fraction of quenched galaxies. While TNG colour distributions are clearly bimodal, this is not the case for the SFR logarithmic distributions in bins of stellar mass (SFR ≳ 10-3Myr-1). Finally, the slope and z = 0 normalization of the TNG MS are consistent with observational findings; however, the locus of the TNG MS remains lower by about 0.2-0.5 dex at 0.75 ≤ z < 2 than the available observational estimates taken at face value.

published in
Monthly Notices of the Royal Astronomical Society, Volume 485, Issue 4, p.4817-4840, June 2019

links to paper
[ADS][arXiv]

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]

Habouzit et al. (2019)

Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG

by
Habouzit, Mélanie; Genel, Shy; Somerville, Rachel S.; Kocevski, Dale; Hirschmann, Michaela; Dekel, Avishai; Choi, Ena; Nelson, Dylan; Pillepich, Annalisa; Torrey, Paul; Hernquist, Lars; Vogelsberger, Mark; Weinberger, Rainer; Springel, Volker

abstract
We study the connection between active galactic nuclei (AGN) and their host galaxies through cosmic time in the large-scale cosmological IllustrisTNG simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity function, AGN galaxy occupation fraction, and distribution of Eddington ratios, to available observational constraints. The simulations produce a population of BHs in good agreement with observations, but we note an excess of faint AGN in hard X-ray (L_x̃ 10^{43-44} erg/s), and a lower number of bright AGN (L_x\gt 10^{44} erg/s), a conclusion that varies quantitatively but not qualitatively with BH luminosity estimation method. The lower Eddington ratios of the 109 M_{\odot } BHs compared to observations suggest that AGN feedback may be too efficient in this regime. We study galaxy star formation activity and structural properties, and design sample-dependent criteria to identify different galaxy types (star-forming/quiescent, extended/compact) that we apply both to the simulations and observations from the CANDELS fields. We analyse how the simulated and observed galaxies populate the specific star formation rate – stellar mass surface density diagram. A large fraction of the z = 0 M_{\star }≥slant 10^{11} M_{\odot } quiescent galaxies first experienced a compaction phase (i.e. reduction of galaxy size) while still forming stars, and then a quenching event. We measure the dependence of AGN fraction on galaxies’ locations in this diagram. After correcting the simulations with a redshift and AGN luminosity-dependent model for AGN obscuration, we find good qualitative and quantitative agreement with observations. The AGN fraction is the highest among compact star-forming galaxies (16-20{{ per cent}} at z ̃ 1.5-2), and the lowest among compact quiescent galaxies (6-10{{ per cent}} at z ̃ 1.5-2).

published in
Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 4, p.4413-4443, April 2019

links to paper
[ADS][arXiv]

Stevens et al. (2019)

Atomic hydrogen in IllustrisTNG galaxies: the impact of environment parallelled with local 21-cm surveys

by
Stevens, Adam R. H.; Diemer, Benedikt; Lagos, Claudia del P.; Nelson, Dylan; Pillepich, Annalisa; Brown, Toby; Catinella, Barbara; Hernquist, Lars; Weinberger, Rainer; Vogelsberger, Mark; Marinacci, Federico

abstract
We investigate the influence of environment on the cold-gas properties of galaxies at z = 0 within the TNG100 cosmological, magnetohydrodynamic simulation, part of the IllustrisTNG suite. We extend previous post-processing methods for breaking gas cells into their atomic and molecular phases, and build detailed mocks to comprehensively compare to the latest surveys of atomic hydrogen (H I) in nearby galaxies, namely ALFALFA and xGASS. We use TNG100 to explore the H I content, star formation activity, and angular momentum of satellite galaxies, each as a function of environment, and find that satellites are typically a factor of ≳3 poorer in H I than centrals of the same stellar mass, with the exact offset depending sensitively on parent halo mass. Due to the large physical scales on which H I measurements are made (̃45-245 kpc), contributions from gas not bound to the galaxy of interest but in the same line of sight crucially lead to larger H I mass measurements in the mocks in many cases, ultimately aligning with observations. This effect is mass-dependent and naturally greater for satellites than centrals, as satellites are never isolated by definition. We also show that H I stripping in TNG100 satellites is closely accompanied by quenching, in tension with observational data that instead favour that H I is preferentially stripped before star formation is reduced.

published in
Monthly Notices of the Royal Astronomical Society, Volume 483, Issue 4, p.5334-5354, March 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]

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