skip to main content

Search for: All records

Creators/Authors contains: "Springel, Volker"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. ABSTRACT Line intensity mapping (LIM) is rapidly emerging as a powerful technique to study galaxy formation and cosmology in the high-redshift Universe. We present LIM estimates of select spectral lines originating from the interstellar medium (ISM) of galaxies and 21 cm emission from neutral hydrogen gas in the Universe using the large volume, high resolution thesan reionization simulations. A combination of subresolution photoionization modelling for H ii regions and Monte Carlo radiative transfer calculations is employed to estimate the dust-attenuated spectral energy distributions (SEDs) of high-redshift galaxies (z ≳ 5.5). We show that the derived photometric properties such as the ultraviolet (UV) luminosity function and the UV continuum slopes match observationally inferred values, demonstrating the accuracy of the SED modelling. We provide fits to the luminosity–star formation rate relation (L–SFR) for the brightest emission lines and find that important differences exist between the derived scaling relations and the widely used low-z ones because the ISM of reionization era galaxies is generally less metal enriched than in their low-redshift counterparts. We use these relations to construct line intensity maps of nebular emission lines and cross-correlate with the 21 cm emission. Interestingly, the wavenumber at which the correlation switches sign (ktransition) depends heavily on themore »reionization model and to a lesser extent on the targeted emission line, which is consistent with the picture that ktransition probes the typical sizes of ionized regions. The derived scaling relations and intensity maps represent a timely state-of-the-art framework for forecasting and interpreting results from current and upcoming LIM experiments.« less
    Free, publicly-accessible full text available June 28, 2023
  2. Abstract Early-type galaxies (ETGs) possess total density profiles close to isothermal, which can lead to non-Gaussian line-of-sight velocity dispersion (LOSVD) under anisotropic stellar orbits. However, recent observations of local ETGs in the MASSIVE Survey reveal outer kinematic structures at 1.5Reff (effective radius) that are inconsistent with fixed isothermal density profiles; the authors proposed varying density profiles as an explanation. We aim to verify this conjecture and understand the influence of stellar assembly on these kinematic features through mock ETGs in IllustrisTNG. We create mock Integral-Field-Unit observations to extract projected stellar kinematic features for 207 ETGs with stellar mass M* ≥ 1011 M⊙ in TNG100-1. The mock observations reproduce the key outer (1.5Reff) kinematic structures in the MASSIVE ETGs, including the puzzling positive correlation between velocity dispersion profile outer slope γouter and the kurtosis h4’s gradient. We find that h4 is uncorrelated with stellar orbital anisotropy beyond Reff; instead we find that the variations in γouter and outer h4 (a good proxy for h4 gradient) are both driven by variations of the density profile at the outskirts across different ETGs. These findings corroborate the proposed conjecture and rule out velocity anisotropy as the origin of non-Gaussian outer kinematic structure in ETGs. Wemore »also find that the outer kurtosis and anisotropy correlate with different stellar assembly components, with the former related to minor mergers or flyby interactions while the latter is mainly driven by major mergers, suggesting distinct stellar assembly origins that decorrelates the two quantities.« less
    Free, publicly-accessible full text available May 19, 2023
  3. ABSTRACT We use the magnetic-hydrodynamical simulation TNG50 to study the evolution of barred massive disc galaxies. Massive spiral galaxies are already present as early as z = 4, and bar formation takes place already at those early times. The bars grow longer and stronger as the host galaxies evolve, with the bar sizes increasing at a pace similar to that of the disc scalelengths. The bar fraction mildly evolves with redshift for galaxies with $M_{*}\ge 10^{10}\rm M_{\odot }$, being greater than $\sim 40{{\ \rm per\ cent}}$ at 0.5 < z < 3 and $\sim 30{{\ \rm per\ cent}}$ at z = 0. When bars larger than a given physical size ($\ge 2\, \rm kpc$) or the angular resolution limit of twice the I-band angular PSF FWHM of the HST are considered, the bar fraction dramatically decreases with increasing redshift, reconciling the theoretical predictions with observational data. We find that barred galaxies have an older stellar population, lower gas fractions, and star formation rates than unbarred galaxies. In most cases, the discs of barred galaxies assembled earlier and faster than the discs of unbarred galaxies. We also find that barred galaxies are typical in haloes with larger concentrations and smaller spin parameters thanmore »unbarred galaxies. Furthermore, the inner regions of barred galaxies are more baryon-dominated than those of unbarred galaxies but have comparable global stellar mass fractions. Our findings suggest that the bar population could be used as a potential tracer of the buildup of disc galaxies and their host haloes. With this paper, we release a catalogue of barred galaxies in TNG50 at six redshifts between z = 4 and 0.« less
    Free, publicly-accessible full text available April 14, 2023
  4. ABSTRACT

    Low-metallicity stars give rise to unique spectacular transients and are of immense interest for understanding stellar evolution. Their importance has only grown further with the recent detections of mergers of stellar mass black holes that likely originate mainly from low-metallicity progenitor systems. Moreover, the formation of low-metallicity stars is intricately linked to galaxy evolution, in particular to early enrichment and to later accretion and mixing of lower metallicity gas. Because low-metallicity stars are difficult to observe directly, cosmological simulations are crucial for understanding their formation. Here, we quantify the rates and locations of low-metallicity star formation using the high-resolution TNG50 magnetohydrodynamical cosmological simulation, and we examine where low-metallicity stars end up at z = 0. We find that $20{{\ \rm per\ cent}}$ of stars with $Z_*\lt 0.1\, \mathrm{Z_\odot }$ form after z = 2, and that such stars are still forming in galaxies of all masses at z = 0 today. Moreover, most low-metallicity stars at z = 0 reside in massive galaxies. We analyse the radial distribution of low-metallicity star formation and discuss the curious case of seven galaxies in TNG50 that form stars from primordial gas even at z = 0.

  5. ABSTRACT We compare the star-forming main sequence (SFMS) of galaxies – both integrated and resolved on 1 kpc scales – between the high-resolution TNG50 simulation of IllustrisTNG and observations from the 3D-HST slitless spectroscopic survey at z ∼ 1. Contrasting integrated star formation rates (SFRs), we find that the slope and normalization of the star-forming main sequence in TNG50 are quantitatively consistent with values derived by fitting observations from 3D-HST with the Prospector Bayesian inference framework. The previous offsets of 0.2–1 dex between observed and simulated main-sequence normalizations are resolved when using the updated masses and SFRs from Prospector. The scatter is generically smaller in TNG50 than in 3D-HST for more massive galaxies with M*> 1010 M⊙, by ∼10–40 per cent, after accounting for observational uncertainties. When comparing resolved star formation, we also find good agreement between TNG50 and 3D-HST: average specific star formation rate (sSFR) radial profiles of galaxies at all masses and radii below, on, and above the SFMS are similar in both normalization and shape. Most noteworthy, massive galaxies with M*> 1010.5 M⊙, which have fallen below the SFMS due to ongoing quenching, exhibit a clear central SFR suppression, in both TNG50 and 3D-HST. In contrast, the original Illustris simulation and a variantmore »TNG run without black hole kinetic wind feedback, do not reproduce the central SFR profile suppression seen in data. In TNG, inside-out quenching is due to the supermassive black hole (SMBH) feedback model operating at low accretion rates.« less
  6. ABSTRACT Supermassive black holes (SMBHs) that reside at the centres of galaxies can inject vast amounts of energy into the surrounding gas and are thought to be a viable mechanism to quench star formation in massive galaxies. Here, we study the $10^{9-12.5}\, \mathrm{M_\odot }$ stellar mass central galaxy population of the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at z = 0, and show how the three components – SMBH, galaxy, and circumgalactic medium (CGM) – are interconnected in their evolution. We find that gas entropy is a sensitive diagnostic of feedback injection. In particular, we demonstrate how the onset of the low-accretion black hole (BH) feedback mode, realized in the IllustrisTNG model as a kinetic, BH-driven wind, leads not only to star formation quenching at stellar masses $\gtrsim 10^{10.5}\, \mathrm{M_\odot }$ but also to a change in thermodynamic properties of the (non-star-forming) gas, both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs increases the average gas entropy, within the galaxy and in the CGM, lengthening typical gas cooling times from $10\!-\!100\, \mathrm{Myr}$ to $1\!-\!10\, \mathrm{Gyr}$, effectively ceasing ongoing star formation and inhibiting radiative cooling and future gas accretion. In practice, the same active galactic nucleusmore »(AGN) feedback channel is simultaneously ‘ejective’ and ‘preventative’ and leaves an imprint on the temperature, density, entropy, and cooling times also in the outer reaches of the gas halo, up to distances of several hundred kiloparsecs. In the IllustrisTNG model, a long-lasting quenching state can occur for a heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies contains regions of low-entropy gas with short cooling times.« less
  7. ABSTRACT We compare predictions for galaxy–galaxy lensing profiles and clustering from the Henriques et al. public version of the Munich semi-analytical model (SAM) of galaxy formation and the IllustrisTNG suite, primarily TNG300, with observations from KiDS + GAMA and SDSS-DR7 using four different selection functions for the lenses (stellar mass, stellar mass and group membership, stellar mass and isolation criteria, and stellar mass and colour). We find that this version of the SAM does not agree well with the current data for stellar mass-only lenses with $M_\ast \gt 10^{11}\, \mathrm{ M}_\odot$. By decreasing the merger time for satellite galaxies as well as reducing the radio-mode active galactic nucleus accretion efficiency in the SAM, we obtain better agreement, both for the lensing and the clustering, at the high-mass end. We show that the new model is consistent with the signals for central galaxies presented in Velliscig et al. Turning to the hydrodynamical simulation, TNG300 produces good lensing predictions, both for stellar mass-only (χ2 = 1.81 compared to χ2 = 7.79 for the SAM) and locally brightest galaxy samples (χ2 = 3.80 compared to χ2 = 5.01). With added dust corrections to the colours it matches the SDSS clustering signal well for red low-mass galaxies. We find that both themore »SAMs and TNG300 predict $\sim 50\, {{\ \rm per\ cent}}$ excessive lensing signals for intermediate-mass red galaxies with 10.2 < log10M*[M⊙] < 11.2 at $r \approx 0.6\, h^{-1}\, \text{Mpc}$, which require further theoretical development.« less
  8. ABSTRACT We present predictions for high redshift (z = 2−10) galaxy populations based on the IllustrisTNG simulation suite and a full Monte Carlo dust radiative transfer post-processing. Specifically, we discuss the H α and H β + $[\rm O \,{\small III}]$ luminosity functions up to z = 8. The predicted H β + $[\rm O \,{\small III}]$ luminosity functions are consistent with present observations at z ≲ 3 with ${\lesssim} 0.1\, {\rm dex}$ differences in luminosities. However, the predicted H α luminosity function is ${\sim }0.3\, {\rm dex}$ dimmer than the observed one at z ≃ 2. Furthermore, we explore continuum spectral indices, the Balmer break at 4000 Å; (D4000) and the UV continuum slope β. The median D4000 versus specific star formation rate relation predicted at z = 2 is in agreement with the local calibration despite a different distribution pattern of galaxies in this plane. In addition, we reproduce the observed AUV versus β relation and explore its dependence on galaxy stellar mass, providing an explanation for the observed complexity of this relation. We also find a deficiency in heavily attenuated, UV red galaxies in the simulations. Finally, we provide predictions for the dust attenuation curves of galaxies at z = 2−6 and investigate their dependence on galaxy colours andmore »stellar masses. The attenuation curves are steeper in galaxies at higher redshifts, with bluer colours, or with lower stellar masses. We attribute these predicted trends to dust geometry. Overall, our results are consistent with present observations of high-redshift galaxies. Future James Webb Space Telecope observations will further test these predictions.« less
  9. ABSTRACT We introduce the Stars and MUltiphase Gas in GaLaxiEs – SMUGGLE model, an explicit and comprehensive stellar feedback model for the moving-mesh code arepo. This novel sub-resolution model resolves the multiphase gas structure of the interstellar medium and self-consistently generates gaseous outflows. The model implements crucial aspects of stellar feedback including photoionization, radiation pressure, energy, and momentum injection from stellar winds and from supernovae. We explore this model in high-resolution isolated simulations of Milky Way like disc galaxies. Stellar feedback regulates star formation to the observed level and naturally captures the establishment of a Kennicutt–Schmidt relation. This result is achieved independent of the numerical mass and spatial resolution of the simulations. Gaseous outflows are generated with average mass loading factors of the order of unity. Strong outflow activity is correlated with peaks in the star formation history of the galaxy with evidence that most of the ejected gas eventually rains down on to the disc in a galactic fountain flow that sustains late-time star formation. Finally, the interstellar gas in the galaxy shows a distinct multiphase distribution with a coexistence of cold, warm, and hot phases.
  10. ABSTRACT The James Webb Space Telescope (JWST) promises to revolutionize our understanding of the early Universe, and contrasting its upcoming observations with predictions of the Λ cold dark matter model requires detailed theoretical forecasts. Here, we exploit the large dynamic range of the IllustrisTNG simulation suite, TNG50, TNG100, and TNG300, to derive multiband galaxy luminosity functions from z = 2 to z = 10. We put particular emphasis on the exploration of different dust attenuation models to determine galaxy luminosity functions for the rest-frame ultraviolet (UV), and apparent wide NIRCam bands. Our most detailed dust model is based on continuum Monte Carlo radiative transfer calculations employing observationally calibrated dust properties. This calibration results in constraints on the redshift evolution of the dust attenuation normalization and dust-to-metal ratios yielding a stronger redshift evolution of the attenuation normalization compared to most previous theoretical studies. Overall we find good agreement between the rest-frame UV luminosity functions and observational data for all redshifts, also beyond the regimes used for the dust model calibrations. Furthermore, we also recover the observed high-redshift (z = 4–6) UV luminosity versus stellar mass relation, the H α versus star formation rate relation, and the H α luminosity function at z = 2. The bright endmore »(MUV > −19.5) cumulative galaxy number densities are consistent with observational data. For the F200W NIRCam band, we predict that JWST will detect ∼80 (∼200) galaxies with a signal-to-noise ratio of 10 (5) within the NIRCam field of view, $2.2\times 2.2 \, {\rm arcmin}^{2}$, for a total exposure time of $10^5\, {\rm s}$ in the redshift range z = 8 ± 0.5. These numbers drop to ∼10 (∼40) for an exposure time of $10^4\, {\rm s}$.« less