Artículos (Física Atómica, Molecular y Nuclear)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10864

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Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime
(IOP Publishing, 2025-06-17) Sun, Haomin; Ball, Justin; Brunner, Stephan; Field, Anthony; Cruz Zabala, Diego José; Viezzer, Eleonora; García Muñoz, Manuel; Física Atómica, Molecular y Nuclear; European Union; EPSRC Energy Programme. United Kingdom
Based on the analysis of a large number of high-fidelity nonlinear gyrokinetic simulations, we propose a novel strategy to improve confinement in spherical tokamak plasmas by combining up-down asymmetric flux surface shaping with the Low Momentum Diffusivity (LMD) regime. We show that the intrinsic momentum flux driven by up-down asymmetry creates strong flow shear in the LMD regime that can significantly reduce energy transport, increasing the critical gradient by up to 25%. In contrast to traditional methods for generating flow shear, such as neutral beam injection, this approach requires no external momentum source and is expected to scale well to large fusion devices. The experimental applicability of this strategy in spherical tokamaks is addressed via simulations by considering actual equilibria from Mega Ampere Spherical Tokamak and a preliminary equilibrium from SMART.
Quantum Machine Learning
(Wiley, 2025-11-11) Lamata Manuel, Lucas; Martín Guerrero, José D.; Física Atómica, Molecular y Nuclear
Introducing SPHINX-MHD: the impact of primordial magnetic fields on the first galaxies, reionization, and the global 21-cm signal
(Oxford University Press, 2021-10) Harley, Katz; Martin-Alvarez, Sergio; Rosdahl, Joakim; Kimm, Taysun; Blaizot, Jérémy; Oñorbe Bernis, José; Teyssier, Romain; Física Atómica, Molecular y Nuclear; Science and Technology Facilities Council (UKRI). United Kingdom; European Commission (EC); National Research Foundation. Korea
We present the first results from SPHINX-MHD, a suite of cosmological radiation-magnetohydrodynamics simulations designed to study the impact of primordial magnetic fields (PMFs) on galaxy formation and the evolution of the intergalactic medium (IGM) during the epoch of reionization. The simulations are among the first to employ multifrequency, on-the-fly radiation transfer and constrained transport ideal MHD in a cosmological context to simultaneously model the inhomogeneous process of reionization as well as the growth of primordial magnetic fields. We run a series of (5 cMpc) 3 cosmological volumes, varying both the strength of the seed magnetic field and its spectral index. We find that PMFs with a spectral index (nB) and a comoving amplitude (B0) that have nB>−0.562 log10 B0 1nG −3.35 produce electron optical depths (τ e) that are inconsistent with CMB constraints due to the unrealistically early collapse of low-mass dwarf galaxies. For nB ≥ −2.9, our constraints are considerably tighter than the ∼nG constraints from Planck. PMFs that do not satisfy our constraints have little impact on the reionization history or the shape of the UV luminosity function. Likewise, detecting changes in the Ly α forest due to PMFs will be challenging because photoionization and photoheating efficiently smooth the density field. However, we find that the first absorption feature in the global 21-cm signal is a particularly sensitive indicator of the properties of the PMFs, even for those that satisfy our τ e constraint. Furthermore, strong PMFs can marginally increase the escape of LyC photons by up to 25 per cent and shrink the effective radii of galaxies by ∼ 44 per cent which could increase the completeness fraction of galaxy surveys. Finally, our simulations show that surveys with a magnitude limit of MUV,1500Å = −13 can probe the sources that provide the majority of photons for reionization out to z = 12
Predicting halo occupation and galaxy assembly bias with machine learning
(Oxford University Press, 2021-11) Xu, Xianju; Kumar, Saurabh; Zehavi, Idit; Contreras Hantke, Sergio Antonio; Física Atómica, Molecular y Nuclear; National Science Foundation (NSF). United States
Understanding the impact of halo properties beyond halo mass on the clustering of galaxies (namely galaxy assembly bias) remains a challenge for contemporary models of galaxy clustering. We explore the use of machine learning to predict the halo occupations and recover galaxy clustering and assembly bias in a semi-analytic galaxy formation model. For stellar mass selected samples, we train a random forest algorithm on the number of central and satellite galaxies in each dark matter halo. With the predicted occupations, we create mock galaxy catalogues and measure the clustering and assembly bias. Using a range of halo and environment properties, we find that the machine learning predictions of the occupancy variations with secondary properties, galaxy clustering, and assembly bias are all in excellent agreement with those of our target galaxy formation model. Internal halo properties are most important for the central galaxies prediction, while environment plays a critical role for the satellites. Our machine learning models are all provided in a usable format. We demonstrate that machine learning is a powerful tool for modelling the galaxy–halo connection, and can be used to create realistic mock galaxy catalogues which accurately recover the expected occupancy variations, galaxy clustering, and galaxy assembly bias, imperative for cosmological analyses of upcoming surveys.
Probing reionization and early cosmic enrichment with the Mg II forest
(Oxford University Press, 2021-09) Hennawi, Joseph F.; Davies, Frederick B.; Wang, Feige; Oñorbe Bernis, José; Física Atómica, Molecular y Nuclear; National Science Foundation (NSF). United States
Because the same massive stars that reionized the intergalactic medium (IGM) inevitably exploded as supernovae that polluted the Universe with metals, the history of cosmic reionization and enrichment is intimately intertwined. While the overly sensitive Ly α transition completely saturates in a neutral IGM, strong low-ionization metal lines like the Mg II λ2796, λ2804 doublet will give rise to a detectable ‘metal-line forest’ if the metals produced during reionization (Z ∼ 10−3 Z) permeate the neutral IGM. We simulate the Mg II forest for the first time by combining a large hydrodynamical simulation with a seminumerical reionization topology, assuming a simple enrichment model where the IGM is uniformly suffused with metals. In contrast to the traditional approach of identifying discrete absorbers, we treat the absorption as a continuous random field and measure its two-point correlation function, leveraging techniques from precision cosmology. We show that a realistic mock data set of 10 James Webb Space Telescope spectra can simultaneously determine the Mg abundance, [Mg/H], with a 1σ precision of 0.02 dex and measure the global neutral fraction xH I to 5 per cent for a Universe with xH I = 0.74 and [Mg/H] = −3.7. Alternatively, if the IGM is pristine, a null detection of the Mg II forest would set a stringent upper limit on the IGM metallicity of [Mg/H] < −4.4 at 95 per cent credibility, assuming xH I > 0.5 from another probe. Concentrations of metals in the circumgalactic environs of galaxies can significantly contaminate the IGM signal, but we demonstrate how these discrete absorbers can be easily identified and masked such that their impact on the correlation function is negligible. The Mg II forest thus has tremendous potential to precisely constrain the reionization and enrichment history of the Universe.
Simultaneous modelling of matter power spectrum and bispectrum in the presence of baryons
(Oxford University Press, 2021-05) Aricó, Giovanni; Angulo, Raúl Esteban; Hernández-Monteagudo, C.; Contreras Hantke, Sergio Antonio; Zennaro, Matteo; Física Atómica, Molecular y Nuclear; European Commission (EC)
We demonstrate that baryonification algorithms, which displace particles in gravity-only simulations according to physically motivated prescriptions, can simultaneously capture the impact of baryonic physics on the two and three-point statistics of matter. Specifically, we show that our implementation of a baryonification algorithm jointly fits the changes induced by baryons on the power spectrum and equilateral bispectrum on scales up to k = 5h Mpc−1 and redshifts 0 ≤ z ≤ 2, as measured in six different cosmological hydrodynamical simulations. The accuracy of our fits is typically ∼ 1 per cent for the power spectrum, and for the equilateral and squeezed bispectra, which somewhat degrades to ∼ 3 per cent for simulations with extreme feedback prescriptions. Our results support the physical assumptions underlying baryonification approaches and encourage their use in interpreting weak gravitational lensing and other cosmological observables.
The assembly bias of emission-line galaxies
(Oxford University Press, 2021-09) Jiménez, Esteban; Padilla, Nelson; Contreras Hantke, Sergio Antonio; Zehavi, Idit; Baugh, Carlton M.; Orsi, Álvaro; Física Atómica, Molecular y Nuclear; National Science Foundation (NSF). United States; European Union (UE)
The next generation of spectroscopic surveys will target emission-line galaxies (ELGs) to produce constraints on cosmological parameters. We study the large-scale structure traced by ELGs using a combination of a semi-analytical model of galaxy formation, a code that computes the nebular emission from H II regions using the properties of the interstellar medium, and a large-volume, high-resolution N-body simulation. We consider fixed number density samples where galaxies are selected by their H α, [O III] λ5007, or [O II] λλ3727–3729 emission-line luminosities. We investigate the assembly bias signatures of these samples, and compare them to those of stellar mass- and star formation rate-selected samples. Interestingly, we find that the [O III]- and [O II]-selected samples display scale-dependent bias on large scales and that their assembly bias signatures are also scale dependent. Both these effects are more pronounced for lower number density samples. The [O III] and [O II] emitters that contribute most to the scale dependence tend to have a low gas-phase metallicity and are preferentially found in low-density regions. We also measure the baryon acoustic oscillation (BAO) feature and the β parameter related to the growth rate of overdensities. We find that the scale of the BAO peak is roughly the same for all selections and that β is scale dependent at large scales. Our results suggest that ELG samples include environmental effects that should be modelled in order to remove potential systematic errors that could affect the estimation of cosmological parameters.
The BACCO simulation project: a baryonification emulator with neural networks
(Oxford University Press, 2021-09) Aricó, Giovanni; Angulo, Raúl Esteban; Contreras Hantke, Sergio Antonio; Ondaro-Mallea, Lurdes; Pellejero-Ibáñez, Marcos; Zennaro, Matteo; Física Atómica, Molecular y Nuclear; European Commission (EC)
We present a neural network emulator for baryonic effects in the non-linear matter power spectrum. We calibrate this emulator using more than 50 000 measurements in a 15D parameter space, varying cosmology and baryonic physics. Baryonic physics is described through a baryonification algorithm, which has been shown to accurately capture the relevant effects on the power spectrum and bispectrum in state-of-the-art hydrodynamical simulations. Cosmological parameters are sampled using a cosmology-rescaling approach including massive neutrinos and dynamical dark energy. The specific quantity we emulate is the ratio between matter power spectrum with baryons and gravity only, and we estimate the overall precision of the emulator to be 2–3 per cent, at scales k < 5 h Mpc−1 and redshifts 0
The cosmological dependence of halo and galaxy assembly bias
(Oxford University Press, 2021-11) Contreras Hantke, Sergio Antonio; Chaves-Montero, Jonás; Zennaro, Matteo; Angulo, Raúl Esteban; Física Atómica, Molecular y Nuclear; European Commission (EC)
One of the main predictions of excursion set theory is that the clustering of dark matter haloes only depends on halo mass. However, it has been long established that the clustering of haloes also depends on other properties, including formation time, concentration, and spin; this effect is commonly known as halo assembly bias (HAB). We use a suite of gravity-only simulations to study the dependence of HAB on cosmology; these simulations cover cosmological parameters spanning 10σ around stateof-the-art best-fitting values, including standard extensions of the CDM paradigm such as neutrino mass and dynamical dark energy. We find that, when studying the peak height-bias relation, the strength of HAB presents variations smaller than 0.05 dex across all cosmologies studied for concentration- and spin-selected haloes, letting us conclude that the dependence of HAB upon cosmology is negligible. We then study the dependence of galaxy assembly bias (i.e. the manifestation of HAB in galaxy clustering) on cosmology using subhalo abundance matching. We find that galaxy assembly bias also presents very small dependence upon cosmology (∼ 2 per cent–4 per cent of the total clustering); on the other hand, we find that the dependence of this signal on the galaxy formation parameters of our galaxy model is much stronger. Taken together, these results let us conclude that the dependence of halo and galaxy assembly bias on cosmology is practically negligible.
Erratum: The host dark matter haloes of [O II] emitters at 0.5 < z < 1.5
(Oxford University Press, 2021-05) González-Pérez, Violeta; Comparat, J.; Norberg, P.; Baugh, Carlton; Contreras Hantke, Sergio Antonio; Lacey, Cedric; Humphries, J.; Física Atómica, Molecular y Nuclear
Improving IGM temperature constraints using wavelet analysis on high-redshift quasars
(Oxford University Press, 2021-12) Wolfson, Molly; Hennawi, Joseph F.; Davies, Frederick B.; Oñorbe Bernis, José; Hiss, Hector; Lukic, Zarija; Física Atómica, Molecular y Nuclear; National Science Foundation. United States
The thermal state of the intergalactic medium contains vital information about the epoch of reionization, one of the most transformative yet poorly understood periods in the young Universe. This thermal state is encoded in the small-scale structure of Lyman-α (Ly α) absorption in quasar spectra. The 1D flux power spectrum measures the average small-scale structure along quasar sightlines. At high redshifts, where the opacity is large, averaging mixes high signal-to-noise ratio transmission spikes with noisy absorption troughs. Wavelet amplitudes are an alternate statistic that maintains spatial information while quantifying fluctuations at the same spatial frequencies as the power spectrum, giving them the potential to more sensitively measure the small-scale structure. Previous Ly α forest studies using wavelet amplitude probability density functions (PDFs) used limited spatial frequencies and neglected strong correlations between PDF bins and across wavelets scales, resulting in suboptimal and unreliable parameter inference. Here we present a novel method for performing statistical inference using wavelet amplitude PDFs that spans the full range of spatial frequencies probed by the power spectrum and that fully accounts for these correlations. We applied this procedure to realistic mock data drawn from a simple thermal model parametrized by the temperature at mean density, T0, and find that wavelets deliver 1σ constraints on T0 that are on average 7 per cent more sensitive at z = 5 (12 per cent at z = 6) than those from the power spectrum. We consider the possibility of combing wavelet PDFs with the power, but find that this does not lead to improved sensitivity.
Evaluating hydrodynamical simulations with green valley galaxies
(Oxford University Press, 2021-04) Angthopo, J.; Negri, Andrea; Ferreras Páez, Ignacio Alfonso; Rosa, I. G. de la; Dalla Vecchia, Claudio; Pillepich, Annalisa; Física Atómica, Molecular y Nuclear; Ministerio de Ciencia, Innovación y Universidades (MICIU). España
We test cosmological hydrodynamical simulations of galaxy formation regarding the properties of the blue cloud (BC), green valley (GV), and red sequence (RS), as measured on the 4000Å break strength versus stellar mass plane at z = 0.1. We analyse the RefL0100N1504 run of EAGLE and the TNG100 run of IllustrisTNG project, by comparing them with the Sloan Digital Sky Survey (SDSS), while taking into account selection bias. Our analysis focuses on the GV, within stellar mass log M/M 10–11, selected from the bimodal distribution of galaxies on the Dn(4000) versus stellar mass plane, following Angthopo et al. methodology. Both simulations match the fraction of AGN in the GV. However, they overproduce quiescent GV galaxies with respect to observations, with IllustrisTNG yielding a higher fraction of quiescent GV galaxies than EAGLE. In both, GV galaxies have older luminosity weighted ages with respect to the SDSS, while a better match is found for mass-weighted ages. We find EAGLE GV galaxies quench their star formation early, but undergo later episodes of star formation, matching observations. In contrast, IllustrisTNG GV galaxies have a more extended star formation history, and quench more effectively at later cosmic times, producing the excess of quenched galaxies in GV compared with SDSS, based on the 4000Å break strength. These results suggest the AGN feedback subgrid physics, more specifically, the threshold halo mass for black hole input and the black hole seed mass, could be the primary cause of the overproduction of quiescent galaxies found with respect to the observational constraints.
Dissecting and modelling galaxy assembly bias
(Oxford University Press, 2021-04) Xu, Xiaju; Zehavi, Idit; Contreras Hantke, Sergio Antonio; Física Atómica, Molecular y Nuclear; National Science Foundation (NSF). United States
haloes’ assembly history and environment impact galaxy clustering (a.k.a. galaxy assembly bias; GAB), remains a complex and challenging problem. Using a semi-analytic galaxy formation model, we study the individual contributions of different secondary halo properties to the GAB signal. These are obtained by comparing the clustering of stellar-mass selected samples to that of shuffled samples where the galaxies are randomly reassigned to haloes of fixed mass and a specified secondary halo property. We explore a large range of internal halo properties and environmental measures. We find that commonly used properties like halo age or concentration amount to only 20–30 per cent of the signal, while the smoothed matter density or the tidal anisotropy can account for the full level of GAB (though care should be given to the specific definition). For the ‘successful’ measures, we examine the occupancy variations and the associated changes in the halo occupation function parameters. These are used to create mock catalogues that reproduce the full level of GAB. Finally, we propose a practical modification of the standard halo occupation distribution model, which can be tuned to any level of assembly bias. Fitting the parameters to our semi-analytic model, we demonstrate that the corresponding mock catalogue recovers the target level of GAB as well as the occupancy variations. Our results enable producing realistic mock catalogues and directly inform theoretical modelling of assembly bias and attempts to detect it in the Universe.
A flexible subhalo abundance matching model for galaxy clustering in redshift space
(Oxford University Press, 0201-11) Contreras Hantke, Sergio Antonio; Angulo, Raúl Esteban; Zennaro, Matteo; Física Atómica, Molecular y Nuclear; European Commission (EC)
We develop an extension of subhalo abundance matching (SHAM) capable of accurately reproducing the real and redshift-space clustering of galaxies in a state-of-the-art hydrodynamical simulation. Our method uses a low-resolution gravity-only simulation and it includes orphan and tidal disruption prescriptions for satellite galaxies, and a flexible amount of galaxy assembly bias. Furthermore, it includes recipes for star formation rate (SFR) based on the dark matter accretion rate. We test the accuracy of our model against catalogues of stellar-mass- and SFR-selected galaxies in the TNG300 hydrodynamic simulation. By fitting a small number of free parameters, our extended SHAM reproduces the projected correlation function and redshift-space multipoles for number densities 10−3 − 10−2 h3Mpc−3 , at z = 1 and z = 0, and for scales r ∈ [0.3 − 20]h−1Mpc. Simultaneously, the SHAM results also retrieve the correct halo occupation distribution, the level of galaxy assembly bias, and higher order statistics present in the TNG300 galaxy catalogues. As an application, we show that our model simultaneously fits the projected correlation function of the SDSS in three disjoint stellar mass bins, with an accuracy similar to that of TNG300 galaxies. This SHAM extension can be used to get accurate clustering prediction even when using low and moderate-resolution simulations.
A flexible modelling of galaxy assembly bias
(Oxford University Press, 2021-07) Contreras Hantke, Sergio Antonio; Angulo, Raúl Esteban; Zennaro, Matteo; Física Atómica, Molecular y Nuclear; European Commission (EC)
We use the ILLUSTRIS TNG300 magneto-hydrodynamic simulation, the SAGE semi-analytical model, and the subhalo abundance matching technique (SHAM) to examine the diversity in predictions for galaxy assembly bias (i.e. the difference in the large-scale clustering of galaxies at a fixed halo mass due to correlations with the assembly history and other properties of host haloes). We consider samples of galaxies selected according to their stellar mass or star formation rate at various redshifts. We find that all models predict an assembly bias signal of different magnitude, redshift evolution, and dependence with selection criteria and number density. To model these non-trivial dependences, we propose an extension to the standard SHAM technique so it can include arbitrary amounts of assembly bias. We do this by preferentially selecting subhaloes with the same internal property but different individual large-scale bias. We find that with this model, we can successfully reproduce the galaxy assembly bias signal in either SAGE or the TNG, for all redshifts and galaxy number densities. We anticipate that this model can be used to constrain the level of assembly bias in observations and aid in the creation of more realistic mock galaxy catalogues.
The luminosity of cluster galaxies in the Cluster-EAGLE simulations
(Oxford University Press, 2022-09) Negri, Andrea; Dalla Vecchia, Claudio; López Aguerri, José Alfonso; Bahé, Yannick; Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Union (UE); Dutch Research Council (NWO). Netherlands
We computed the luminosity of simulated galaxies of the C-EAGLE project, a suite of 30 high-resolution zoom-in simulations of galaxy clusters based on the EAGLE simulation. The AB magnitudes are derived for different spectral bands, from ultraviolet to infrared, using the simple stellar population modelling based on the E-MILES stellar spectra library. We take into account obscuration due to dust in star forming regions and diffuse interstellar medium. The g − r colour–stellar mass diagram, at z = 0.1, presents a defined red sequence, reaching g − r 0.8, 0.05 dex redder than EAGLE at high masses, and a well populated blue cloud, when field galaxies are included. The clusters’ inner regions are dominated by red-sequence galaxies at all masses, although a non-negligible amount of blue galaxies are still present. We adopt Bayesian inference to compute the clusters LFs, testing for statistical significance of both single and double Schechter functions. The multicolour LFs at z = 0 show a knee luminosity that peaks in the infrared and increases with the cluster’s mass. The faint-end is weakly dependent on colour and mass and shows an upturn in the optical, bounded between −1.25 and −1.39, just moderately steeper than the field. The simulations reproduce, within the observational errors, the spectroscopic LFs of the Hercules and Abell 85 clusters, including their faint end upturn. C-EAGLE LFs are in broad agreement with observed LFs taken from SDSS and XXL surveys, up to z = 0.67, showing a rather flat faint end when the observational constrains are taken into account.
The impact of ionization morphology and X-ray heating on the cosmological 21-cm skew spectrum
(Oxford University Press, 2024-04) Cook, J. H.; Sreedhar, Balu; Greig, B.; Trott, C. M.; Line, J. L. B.; Qin, Y.; Wyithe, J. S. B.; Física Atómica, Molecular y Nuclear; Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D); ARC Future Fellowship; Australian Research Council LIEF.
The cosmological 21-cm signal offers a potential probe of the early Universe and the first ionizing sources. Current experiments probe the spatially dependent variance (Gaussianity) of the signal through the power spectrum (PS). The signal, ho we ver, is expected to be highly non-Gaussian due to the complex topology of reionization and X-ray heating. We investigate the non- Gaussianities of X-ray heating and reionization, by calculating the skew spectrum (SS) of the 21-cm signal using MERAXES , which couples a semi-analytic galaxy population with seminumerical reionization simulations. The SS is the cross-spectrum of the quadratic temperature brightness field with itself. We generate a set of seven simulations from z = 30 to 5, varying the halo mass threshold for hosting star formation, the X-ray luminosity per star formation rate, and the minimum X-ray energy escaping host galaxies. We find the SS is predominantly ne gativ e as a function of redshift, transitioning to positive towards the start of reionization, and peaking during the mid-point of reionization. We do not see a ne gativ e dip in the SS during reionization, likely due to the specifics of modelling ionization sources. We normalize the SS by the PS during reionization isolating the non-Gaussianities. We find a trough ( k ∼0 . 1 Mpc −1 ) and peak ( k ∼0 . 4 −1 Mpc −1 ) in the normalized SS during the mid-to-late periods of reionization. These correlate to the ionization topology, and neutral islands in the IGM. We calculate the cosmic variance of the normalized SS, and find these features are detectable in the absence of foregrounds with the SKA LOW.
Consistent clustering and lensing of SDSS-III BOSS galaxies with an extended abundance matching formalism
(Oxford University Press, 2023-10) Contreras Hantke, Sergio Antonio; Chaves-Montero, Jonás; Angulo, Raúl Esteban; Física Atómica, Molecular y Nuclear; European Union (UE); Barcelona Supercomputing Center
Several analyses have shown that cold dark matter-based models cannot jointly describe the clustering (GC) and galaxy–galaxy lensing (GGL) of galaxies in the Sloan Digital Sky Survey-III (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS), which is commonly known as the ‘lensing-is-low problem’. In this work, we show that an extension of Subhalo Abundance Matching, dubbed SHAMe, successfully solves this problem. First, we show that this model accurately reproduces the GC and GGL of a mock galaxy sample in the TNG300 hydrodynamic simulation with properties analogous to those of BOSS galaxies. Then, we switch our attention to observed BOSS galaxies at z = 0.31−0.43, and we attempt to reproduce their GC and GGL by evaluating SHAMe on two different simulations: one adopting best-fitting cosmological parameters from Planck and the other from weak gravitational lensing surveys (Low S8), where the amplitude of matter fluctuations is lower for the latter. We find excellent agreement between SHAMe predictions and observations for both cosmologies, indicating that the lensing-is-low problem originates from approximations in previous theoretical descriptions of the data. The main difference between SHAMe results in these cosmologies is the level of galaxy assembly bias, which is approximately 20 per cent and 10 per cent for Planck and Low S8, respectively. These results highlight the dangers of employing oversimplified models to analyse current large-scale structure data sets, and the need for realistic yet flexible descriptions of the galaxy–halo connection.
The cosmology dependence of the concentration–mass–redshift relation
(Oxford University Press, 2022-12) López-Cano, Daniel; Angulo, Raúl Esteban; Ludlow, Aaron D.; Zennaro, Matteo; Contreras Hantke, Sergio Antonio; Chaves-Montero, Jonás; Aricó, Giovanni; Física Atómica, Molecular y Nuclear; European Research Council (ERC); Ministerio de Ciencia, Innovación y Universidades (MICIU). España
The concentrations of dark matter haloes provide crucial information about their internal structure and how it depends on mass and redshift – the so-called concentration–mass–redshift relation, denoted c(M, z). We present here an extensive study of the cosmology-dependence of c(M, z) that is based on a suite of 72 gravity-only, full N-body simulations in which the following cosmological parameters were varied: σ8, M, b, ns, h, Mν , w0, and wa. We characterize the impact of these parameters on concentrations for different halo masses and redshifts. In agreement with previous works, and for all cosmologies studied, we find that there exists a tight correlation between the characteristic densities of dark matter haloes within their scale radii, r−2, and the critical density of the universe at a suitably defined formation time. This finding, when combined with excursion set modelling of halo formation histories, allows us to accurately predict the concentrations of dark matter haloes as a function of mass, redshift, and cosmology. We use our simulations to test the reliability of a number of published models for predicting halo concentration and highlight when they succeed or fail to reproduce the cosmological c(M, z) relation.
Implications of z 12 JWST galaxies for galaxy formation at high redshift
(Oxford University Press, 2023-11) Yuxiang, Qin; Sreedhar, Balu; Barton Wyithe, James Stuart; Física Atómica, Molecular y Nuclear; Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)
Using a semi-analytic galaxy formation model, we study analogues of eight z 12 galaxies recently discovered by James Webb Space Telescope (JWST). We select analogues from a cosmological simulation with a (311 cMpc)3 volume and an effective particle number of 1012 enabling the resolution of every atomic-cooling galaxy at z ≤ 20. We vary model parameters to reproduce the observed ultraviolet (UV) luminosity function at 5 < z < 13, aiming for a statistically representative high-redshift galaxy mock catalogue. Using the forward-modelled JWST photometry, we identify analogues from this catalogue and study their properties as well as possible evolutionary paths and local environment. We find faint JWST galaxies (MUV − 19.5) to remain consistent with the standard galaxy formation model and that our fiducial catalogue includes large samples of their analogues. The properties of these analogues broadly agree with conventional spectral energy distribution-fitting results, except for having systematically lower redshifts due to the evolving ultraviolet luminosity function, and for having higher specific star formation rates as a result of burstier histories in our model. On the other hand, only a handful of bright galaxy analogues can be identified for the observed z ∼ 12 galaxies. Moreover, in order to reproduce the z 16 JWST galaxy candidates, boosting star-forming efficiencies through reduced feedback regulation and increased gas depletion rate is necessary relative to models of lower redshift populations. This suggests star formation in the first galaxies could differ significantly from their lower redshift counterparts. We also find that these candidates are subject to low-redshift contamination, which is present in our fiducial results as both the dusty or quiescent galaxies at z ∼ 5.

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