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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. [ABSTRACT FROM AUTHOR]

Models for massive black holes are a key ingredient for modern cosmological simulations of galaxy formation. The necessity of efficient AGN feedback in these simulations makes it essential to model the formation, growth and evolution of massive black holes, and parameterize these complex processes in a simplified fashion. While the exact formation mechanism is secondary for most galaxy formation purposes, accretion modeling turns out to be crucial. It can be informed by the properties of the high redshift quasars, accreting close to their Eddington limit, by the quasar luminosity function at peak activity and by low-redshift scaling relations. The need for halo-wide feedback implies a feedback-induced reduction of the accretion rate towards low redshift, amplifying the cosmological trend towards lower accretion rates at low redshift. [ABSTRACT FROM AUTHOR]

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– M 20 and 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– M 20 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. [ABSTRACT FROM AUTHOR]

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 |$10^{9.5} \, \mathrm{M_{\odot }}$| and with host halo masses in the range |$10^{13} \le M_{\rm 200c}/\, \mathrm{M_{\odot }}\le 10^{14.6}$|⁠. 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 / R 200c ≳ 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. [ABSTRACT FROM AUTHOR]

We explore the abundance, spatial distribution, and physical properties of the OVI, OVII, and OVIII ions of oxygen in circumgalactic and intergalactic media (the CGM, IGM, and WHIM). We use the TNG100 and TNG300 large volume cosmological magnetohydrodynamical simulations. Modelling the ionization states of simulated oxygen, we find good agreement with observations of the low-redshiftOVI column density distribution function (CDDF), and present its evolution for all three ions from z = 0 to z = 4. Producing mock quasar absorption line spectral surveys, we show that the IllustrisTNG simulations are fully consistent with constraints on the OVI content of the CGM from COS-haloes and other low-redshift observations, producing columns as high as observed. We measure the total amount of mass and average column densities of each ion using hundreds of thousands of simulated galaxies spanning 1011 < Mhalo/M⊙<1015 corresponding to 109 < M⊙/M⊙<1012 in stellar mass. Stacked radial profiles of OVI are computed in 3D number density and 2D projected column density, decomposing into 1-halo and 2-halo terms. Relating halo OVI to properties of the central galaxy, we find a correlation between the (g - r) colour of a galaxy and the total amount of OVI in its CGM. In comparison to the COS-Haloes finding, this leads to a dichotomy of columns around star-forming versus passive galaxies at fixed stellar (or halo) mass. We demonstrate that this correlation is a direct result of black hole feedback associated with quenching and represents a causal consequence of galactic-scale baryonic feedback impacting the physical state of the circumgalactic medium. [ABSTRACT FROM AUTHOR]

Hydrodynamical simulations of galaxy formation have now reached sufficient volume to make precision predictions for clustering on cosmologically relevant scales. Here, we use our new IllustrisTNG simulations to study the non-linear correlation functions and power spectra of baryons, dark matter, galaxies, and haloes over an exceptionally large range of scales. We find that baryonic effects increase the clustering of dark matter on small scales and damp the total matter power spectrum on scales up to k ~ 10 h Mpc-1 by 20 per cent. The non-linear two-point correlation function of the stellar mass is close to a power-law over a wide range of scales and approximately invariant in time from very high redshift to the present. The two-point correlation function of the simulated galaxies agrees well with Sloan Digital Sky Survey at its mean redshift z 0.1, both as a function of stellar mass and when split according to galaxy colour, apart from a mild excess in the clustering of red galaxies in the stellar mass range of109-1010 h-2M. Given this agreement, the TNG simulations can make valuable theoretical predictions for the clustering bias of different galaxy samples. We find that the clustering length of the galaxy autocorrelation function depends strongly on stellar mass and redshift. Its power-law slope y is nearly invariant with stellar mass, but declines from γ ~ 1.8 at redshift z = 0 to y ~ 1.6 at redshift z ~ 1, beyond which the slope steepens again. We detect significant scale dependences in the bias of different observational tracers of largescale structure, extending well into the range of the baryonic acoustic oscillations and causing nominal (yet fortunately correctable) shifts of the acoustic peaks of around ~5 per cent. [ABSTRACT FROM AUTHOR]

The IllustrisTNG project is a new suite of cosmological magnetohydrodynamical simulations of galaxy formation performed with the AREPO code and updated models for feedback physics. Here, we introduce the first two simulations of the series, TNG100 and TNG300, and quantify the stellar mass content of about 4000 massive galaxy groups and clusters (1013 ≤ M200c/M☉ ≤ 1015) at recent times (z ≤ 1). The richest clusters have half of their total stellar mass bound to satellite galaxies, with the other half being associated with the central galaxy and the diffuse intracluster light. Haloes more massive than about 5 × 1014M☉ have more diffuse stellar mass outside 100 kpc than within 100 kpc, with power-law slopes of the radial mass density distribution as shallow as the dark matter's (-3.5 ≲ α3D ≲ -3). Total halo mass is a very good predictor of stellar mass, and vice versa: at z = 0, the 3D stellar mass measured within 30 kpc scales as (M500c)0.49 with a∼0.12 dex scatter. This is possibly too steep in comparison to the available observational constraints, even though the abundance of The Next Generation less-massive galaxies (≲1011M☉ in stars) is in good agreement with the measured galaxy stellar mass functions at recent epochs. The 3D sizes of massive galaxies fall too on a tight (∼0.16 dex scatter) power-law relation with halo mass, with rstars 0.5 (M200c)0.53. Even more fundamentally, halo mass alone is a good predictor for the whole stellar mass profiles beyond the inner few kiloparsecs, and we show how on average these can be precisely recovered given a single-mass measurement of the galaxy or its halo. [ABSTRACT FROM AUTHOR]

We introduce the first two simulations of the IllustrisTNG project, a next generation of cosmological magnetohydrodynamical simulations, focusing on the optical colours of galaxies. We explore TNG100, a rerun of the original Illustris box, and TNG300, which includes 2 × 25003 resolution elements in a volume 20 times larger. Here, we present first results on the galaxy colour bimodality at low redshift. Accounting for the attenuation of stellar light by dust, we compare the simulated (g - r) colours of 109 12.5 galaxies to the observed distribution from the Sloan Digital Sky Survey.We find a striking improvement with respect to the original Illustris simulation, as well as excellent quantitative agreement with the observations, with a sharp transition in median colour from blue to red at a characteristic M* ∼ 1010.5☉. Investigating the build-up of the colour-mass plane and the formation of the red sequence, we demonstrate that the primary driver of galaxy colour transition is supermassive black hole feedback in its low accretion state. Across the entire population the median colour transition time-scale Δtgreen is ∼1.6Gyr, a value which drops for increasingly massive galaxies. We find signatures of the physical process of quenching: at fixed stellar mass, redder galaxies have lower star formation rates, gas fractions, and gas metallicities; their stellar populations are also older and their large-scale interstellar magnetic fields weaker than in bluer galaxies. Finally, we measure the amount of stellar mass growth on the red sequence. Galaxies with M* >1011☉ which redden at z < 1 accumulate on average ∼25 per cent of their final z = 0 mass post-reddening; at the same time, ∼18 per cent of such massive galaxies acquire half or more of their final stellar mass while on the red sequence. [ABSTRACT FROM AUTHOR]

We analyse scaling relations and evolution histories of galaxy sizes in TNG100, part of the IllustrisTNG simulation suite. Observational qualitative trends of size with stellar mass, star formation rate and redshift are reproduced, and a quantitative comparison of projected r band sizes at 0 < z < 2 shows agreement to much better than 0.25 dex. We follow populations of z = 0 galaxies with a range of masses backwards in time along their main progenitor branches, distinguishing between main-sequence and quenched galaxies. Our main findings are as follows. (i) AtM*,z=0 < 109.5M☉, the evolution of the median main progenitor differs, with quenched galaxies hardly growing in median size before quenching, whereas main-sequence galaxies grow their median size continuously, thus opening a gap from the progenitors of quenched galaxies. This is partly because the main-sequence high-redshift progenitors of quenched z = 0 galaxies are drawn from the lower end of the size distribution of the overall population of main-sequence high-redshift galaxies. (ii) Quenched galaxies with M*,z=0 > 109.5M☉ experience a steep size growth on the size-mass plane after their quenching time, but with the exception of galaxies with M*,z=0 < 1011M☉, the size growth after quenching is small in absolute terms, such that most of the size (and mass) growth of quenched galaxies (and its variation among them) occurs while they are still on the main sequence. After they become quenched, the size growth rate of quenched galaxies as a function of time, as opposed to versus mass, is similar to that of main-sequence galaxies. Hence, the size gap is retained down to z = 0. [ABSTRACT FROM AUTHOR]

The distribution of metals in the intra-cluster medium (ICM) encodes important information about the enrichment history and formation of galaxy clusters. Here, we explore the metal content of clusters in IllustrisTNG -- a new suite of galaxy formation simulations building on the Illustris project. Our cluster sample contains 20 objects in TNG100 -- a ~(100 Mpc)³ volume simulation with 2 x 1820³ resolution elements, and 370 objects in TNG300 -- a ~(300 Mpc)³ volume simulation with 2 x 2500³ resolution elements. The ɀ = 0 metallicity profiles agree with observations, and the enrichment history is consistent with observational data going beyond ɀ~1, showing nearly no metallicity evolution. The abundance profiles vary only minimally within the cluster samples, especially in the outskirts with a relative scatter of ~15 per cent. The average metallicity profile flattens towards the centre, where we find a logarithmic slope of -0.1 compared to -0.5 in the outskirts. Cool core clusters have more centrally peaked metallicity profiles (~0.8 solar) compared to non-cool core systems (~0.5 solar), similar to observational trends. Si/Fe and O/Fe radial profiles follow positive gradients. The outer abundance profiles do not evolve below ɀ ~ 2, whereas the inner profiles flatten towards ɀ = 0. More than ~80 per cent of the metals in the ICM have been accreted from the proto-cluster environment, which has been enriched to ~0.1 solar already at ɀ ~ 2. We conclude that the intra-cluster metal distribution is uniform among our cluster sample, nearly time-invariant in the outskirts for more than 10 Gyr, and forms through a universal enrichment history. [ABSTRACT FROM AUTHOR]

We introduce an updated physical model to simulate the formation and evolution of galaxies in cosmological, large-scale gravity+magnetohydrodynamical simulations with the moving mesh code AREPO. The overall framework builds upon the successes of the Illustris galaxy formation model, and includes prescriptions for star formation, stellar evolution, chemical enrichment, primordial and metal-line cooling of the gas, stellar feedback with galactic outflows, and black hole formation, growth and multimode feedback. In this paper, we give a comprehensive description of the physical and numerical advances that form the core of the IllustrisTNG (The Next Generation) framework. We focus on the revised implementation of the galactic winds, of which we modify the directionality, velocity, thermal content and energy scalings, and explore its effects on the galaxy population. As described in earlier works, the model also includes a new black-hole-driven kinetic feedback at low accretion rates, magnetohydrodynamics and improvements to the numerical scheme. Using a suite of (25Mpc h-1)3 cosmological boxes, we assess the outcome of the new model at our fiducial resolution. The presence of a selfconsistently amplified magnetic field is shown to have an important impact on the stellar content of 1012M⊙ haloes and above. Finally, we demonstrate that the new galactic winds promise to solve key problems identified in Illustris in matching observational constraints and affecting the stellar content and sizes of the low-mass end of the galaxy population. [ABSTRACT FROM AUTHOR]

The inefficiency of star formation in massive elliptical galaxies is widely believed to be caused by the interactions of an active galactic nucleus (AGN) with the surrounding gas. Achieving a sufficiently rapid reddening of moderately massive galaxies without expelling too many baryons has however proven difficult for hydrodynamical simulations of galaxy formation, prompting us to explore a new model for the accretion and feedback effects of supermassive black holes. For high-accretion rates relative to the Eddington limit, we assume that a fraction of the accreted rest mass energy heats the surrounding gas thermally, similar to the 'quasar mode' in previouswork. For low-accretion rates, we invoke a new, pure kinetic feedback model that imparts momentum to the surrounding gas in a stochastic manner. These two modes of feedback are motivated both by theoretical conjectures for the existence of different types of accretion flows as well as recent observational evidence for the importance of kinetic AGN winds in quenching galaxies.We find that a large fraction of the injected kinetic energy in this mode thermalizes via shocks in the surrounding gas, thereby providing a distributed heating channel. In cosmological simulations, the resulting model produces red, non-star-forming massive elliptical galaxies, and achieves realistic gas fractions, black hole growth histories and thermodynamic profiles in large haloes. [ABSTRACT FROM AUTHOR]

JWST has revealed a large population of accreting black holes (BHs) in the early Universe. Recent work has shown that even after accounting for possible systematic biases, the high- z |$M_*{\!-\!}M_{\rm \rm bh}$| relation can be above the local scaling relation by |$\gt 3\sigma$|⁠. To understand the implications of these overmassive high- z BHs, we study the BH growth at |$z\sim 4{\!-\!}7$| using the |$[18~\mathrm{Mpc}]^3$| BRAHMA cosmological simulations with systematic variations of heavy seed models that emulate direct collapse black hole (DCBH) formation. In our least restrictive seed model, we place |$\sim 10^5~{\rm M}_{\odot }$| seeds in haloes with sufficient dense and metal-poor gas. To model conditions for direct collapse, we impose additional criteria based on a minimum Lyman Werner flux (LW flux |$=10~J_{21}$|⁠), maximum gas spin, and an environmental richness criterion. The high- z BH growth in our simulations is merger dominated, with a relatively small contribution from gas accretion. The simulation that includes all the above seeding criteria fails to reproduce an overmassive high- z |$M_*{\!-\!}M_{\rm bh}$| relation consistent with observations (by factor of |$\sim 10$| at |$z\sim 4$|⁠). However, more optimistic models that exclude the spin and environment based criteria are able to reproduce the observed relations if we assume |$\lesssim 750~\mathrm{Myr}$| delay times between host galaxy mergers and subsequent BH mergers. Overall, our results suggest that current JWST observations may be explained with heavy seeding channels if their formation is more efficient than currently assumed DCBH conditions. Alternatively, we may need higher initial seed masses, additional contributions from lighter seeds to BH mergers, and / or more efficient modes for BH accretion. [ABSTRACT FROM AUTHOR]

While the first "seeds" of supermassive black holes (BH) can range from |$\sim 10^2-10^6 \rm ~{\rm M}_{\odot }$|⁠ , the lowest mass seeds (⁠|$\lesssim 10^3~\rm {\rm M}_{\odot }$|⁠) are inaccessible to most cosmological simulations due to resolution limitations. We present our new BRAHMA simulations that use a novel flexible seeding approach to predict the |$z\ge 7$| BH populations for low-mass seeds. We ran two types of boxes that model |$\sim 10^3~\rm {\rm M}_{\odot }$| seeds using two distinct but mutually consistent seeding prescriptions at different simulation resolutions. First, we have the highest resolution |$[9~\mathrm{Mpc}]^3$| (BRAHMA-9-D3) boxes that directly resolve |$\sim 10^3~\rm {\rm M}_{\odot }$| seeds and place them within haloes with dense, metal-poor gas. Second, we have lower resolution, larger volume |$[18~\mathrm{Mpc}]^3$| (BRAHMA-18-E4), and |$\sim [36~\mathrm{Mpc}]^3$| (BRAHMA-36-E5) boxes that seed their smallest resolvable |$\sim 10^4~\&~10^5~\mathrm{{\rm M}_{\odot }}$| BH descendants using new stochastic seeding prescriptions calibrated using BRAHMA-9-D3. The three boxes together probe key BH observables between |$\sim 10^3\,\mathrm{ and}\,10^7~\rm {\rm M}_{\odot }$|⁠. The active galactic nuclei (AGN) luminosity function variations are small (factors of |$\sim 2-3$|⁠) at the anticipated detection limits of potential future X-ray facilities (⁠|$\sim 10^{43}~ \mathrm{ergs~s^{-1}}$| at |$z\sim 7$|⁠). Our simulations predict BHs |$\sim 10-100$| times heavier than the local |$M_*$| versus |$M_{\mathrm{ bh}}$| relations, consistent with several JWST -detected AGN. For different seed models, our simulations merge binaries at |$\sim 1-15~\mathrm{kpc}$|⁠ , with rates of |$\sim 200-2000$| yr−1 for |$\gtrsim 10^3~\rm {\rm M}_{\odot }$| BHs, |$\sim 6-60$| yr−1 for |$\gtrsim 10^4~\rm {\rm M}_{\odot }$| BHs, and up to |$\sim 10$| yr−1 amongst |$\gtrsim 10^5~\rm {\rm M}_{\odot }$| BHs. These results suggest that Laser Interferometer Space Antenna mission has promising prospects for constraining seed models. [ABSTRACT FROM AUTHOR]

The physical origin of the seeds of supermassive black holes (SMBHs), with postulated initial masses ranging from ∼105 M⊙ to as low as ∼102 M⊙, is currently unknown. Most existing cosmological hydrodynamic simulations adopt very simple, ad hoc prescriptions for BH seeding and seed at unphysically high masses ∼105–106 M⊙. In this work, we introduce a novel sub-grid BH seeding model for cosmological simulations that is directly calibrated to high-resolution zoom simulations that explicitly resolve ∼103 M⊙ seeds forming within haloes with pristine, dense gas. We trace the BH growth along galaxy merger trees until their descendants reach masses of ∼104 or 105 M⊙. The results are used to build a new stochastic seeding model that directly seeds these descendants in lower resolution versions of our zoom region. Remarkably, we find that by seeding the descendants simply based on total galaxy mass, redshift and an environmental richness parameter, we can reproduce the results of the detailed gas-based seeding model. The baryonic properties of the host galaxies are well reproduced by the mass-based seeding criterion. The redshift-dependence of the mass-based criterion captures the combined influence of halo growth, dense gas formation, and metal enrichment on the formation of ∼103 M⊙ seeds. The environment-based seeding criterion seeds the descendants in rich environments with higher numbers of neighbouring galaxies. This accounts for the impact of unresolved merger dominated growth of BHs, which produces faster growth of descendants in richer environments with more extensive BH merger history. Our new seed model will be useful for representing a variety of low-mass seeding channels within next-generation larger volume uniform cosmological simulations. [ABSTRACT FROM AUTHOR]

We use deep JWST /NIRSpec R ∼ 1000 slit spectra of 113 galaxies at |$1.7 < z < 3.5$|⁠ , selected from the mass-complete Blue Jay survey, to investigate the prevalence and typical properties of neutral gas outflows at cosmic noon. We detect excess Na  id absorption (beyond the stellar contribution) in 46 per cent of massive galaxies (log  M */M⊙ > 10), with similar incidence rates in star-forming and quenching systems. Half of the absorption profiles are blueshifted by at least 100 km s−1, providing unambiguous evidence for neutral gas outflows. Galaxies with strong Na id absorption are distinguished by enhanced emission line ratios consistent with AGN ionization. We conservatively measure mass outflow rates of 3–100 M⊙ yr−1; comparable to or exceeding ionized gas outflow rates measured for galaxies at similar stellar mass and redshift. The outflows from the quenching systems (log(sSFR)[yr−1] ≲ −10) have mass loading factors of 4–360, and the energy and momentum outflow rates exceed the expected injection rates from supernova explosions, suggesting that these galaxies could possibly be caught in a rapid blowout phase powered by the AGN. Our findings suggest that AGN-driven ejection of cold gas may be a dominant mechanism for fast quenching of star formation at z ∼ 2. [ABSTRACT FROM AUTHOR]

Large-scale outflows driven by supermassive black holes are thought to have a fundamental role in suppressing star formation in massive galaxies. However, direct observational evidence for this hypothesis is still lacking, particularly in the young universe where star-formation quenching is remarkably rapid 1-3 , thus requiring effective removal of gas 4 as opposed to slow gas heating 5,6 . Although outflows of ionized gas are frequently detected in massive distant galaxies 7 , the amount of ejected mass is too small to be able to suppress star formation 8,9 . Gas ejection is expected to be more efficient in the neutral and molecular phases 10 , but at high redshift these have only been observed in starbursts and quasars 11,12 . Here we report JWST spectroscopy of a massive galaxy experiencing rapid quenching at a redshift of 2.445. We detect a weak outflow of ionized gas and a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to quench the star formation. Neither X-ray nor radio activity is detected; however, the presence of a supermassive black hole is suggested by the properties of the ionized gas emission lines. We thus conclude that supermassive black holes are able to rapidly suppress star formation in massive galaxies by efficiently ejecting neutral gas., (© 2024. The Author(s).)