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1.	Charnock, Tom, et al. (författare) Neural physical engines for inferring the halo mass distribution function 2020 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 494:1, s. 50-61 Tidskriftsartikel (refereegranskat)abstract An ambitious goal in cosmology is to forward model the observed distribution of galaxies in the nearby Universe today from the initial conditions of large-scale structures. For practical reasons, the spatial resolution at which this can be done is necessarily limited. Consequently, one needs a mapping between the density of dark matter averaged over similar to Mpc scales and the distribution of dark matter haloes (used as a proxy for galaxies) in the same region. Here, we demonstrate a method for determining the halo mass distribution function by learning the tracer bias between density fields and halo catalogues using a neural bias model. The method is based on the Bayesian analysis of simple, physically motivated, neural network-like architectures, which we denote as neural physical engines, and neural density estimation. As a result, we are able to sample the initial phases of the dark matter density field while inferring the parameters describing the halo mass distribution function, providing a fully Bayesian interpretation of both the initial dark matter density distribution and the neural bias model. We successfully run an upgraded BORG (Bayesian Origin Reconstruction from Galaxies) inference using our new likelihood and neural bias model with halo catalogues derived from full N-body simulations. In preliminary results, we notice there could potentially be orders of magnitude improvement in modelling compared to classical biasing techniques.
2.	Desmond, Harry, et al. (författare) Fifth force constraints from galaxy warps 2018 Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:8 Tidskriftsartikel (refereegranskat)abstract Intragalaxy signals contain a wealth of information on fundamental physics, both the dark sector and the nature of gravity. While so far largely unexplored, such probes are set to rise dramatically in importance as upcoming surveys provide data of unprecedented quantity and quality on galaxy structure and dynamics. In this paper, we use warping of stellar disks to test the chameleon-or symmetron-screened fifth forces which generically arise when new fields couple to matter. We take r-band images of mostly late-type galaxies from the Nasa Sloan Atlas and develop an automated algorithm to quantify the degree of U-shaped warping they exhibit. We then forward model the warp signal as a function of fifth-force strength, Delta G/G(N), and range, lambda(C), and the gravitational environments and internal properties of the galaxies, including full propagation of the non-Gaussian uncertainties. Convolving this fifth-force likelihood function with a Gaussian describing astrophysical and observational noise and then constraining Delta G/G(N) and lambda(C) by Markov chain Monte Carlo, we find the overall likelihood to be significantly increased (Delta log (L) similar or equal to 20) by adding a screened fifth force with lambda(C) similar or equal to 2 Mpc and Delta G/G(N) similar or equal to 0.01. The variation of Delta log (L) with lambda(C) is quantitatively as expected from the correlation of the magnitude of the fifth-force field with the force's range, and a similar model without screening achieves no increase in likelihood over the General Relativistic case Delta G = 0. Although these results are in good agreement with a previous analysis of the same model using offsets between galaxies' stellar and gas mass centroids [H. Desmond et al., Phys. Rev. D 98, 064015 (2018).], we caution that the effects of confounding baryonic and dark matter physics must be thoroughly investigated for the results of the inference to be unambiguous.
3.	Desmond, Harry, et al. (författare) Fifth force constraints from the separation of galaxy mass components 2018 Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:6 Tidskriftsartikel (refereegranskat)abstract One of the most common consequences of extensions to the standard models of particle physics or cosmology is the emergence of a fifth force. While generic fifth forces are tightly constrained at Solar System scales and below, they may escape detection by means of a screening mechanism which effectively removes them in dense environments. We constrain the strength Delta G/G(N) and range lambda(C) of a fifth force with Yukawa coupling arising from a chameleon-or symmetron-screened scalar field-as well as an unscreened fifth force with differential coupling to galactic mass components-by searching for the displacement it predicts between galaxies' stellar and gas mass centroids. Taking data from the Alfalfa survey of neutral atomic hydrogen (HI), identifying galaxies' gravitational environments with the maps of [H. Desmond, P.G. Ferreira, G. Lavaux, and J. Jasche, Mon. Not. R. Astron. Soc. 474, 3152 (2018)] and forward modeling with a Bayesian likelihood framework, we find, with screening included, 6.6 sigma evidence for Delta G > 0 at lambda(C) greater than or similar to 2 Mpc. The maximum-likelihood Delta G/G(N) is 0.025. A similar fifth force model without screening gives no increase in likelihood over the case Delta G = 0 for any lambda(C). Although we validate this result by several methods, we do not claim screened modified gravity to provide the only possible explanation for the data: this conclusion would require knowing that the signal could not be produced by galaxy formation physics. We show also the results of a more conservative-though less well-motivated-noise model which yields only upper limits on Delta G/G(N), ranging from similar to 10(-1) for lambda(C) similar or equal to 0.5 Mpc to similar to few x 10(-4) at lambda(C) similar or equal to 50 Mpc. Corresponding models without screening receive the somewhat stronger bounds similar to few x 10(-3) and similar to few x 10(-4) respectively. We show how these constraints may be improved by future galaxy surveys and identify the key features of an observational program for directly constraining fifth forces on scales beyond the Solar System. This paper provides a complete description of the analysis summarized in [H. Desmond, P.G. Ferreira, G. Lavaux, and J. Jasche, arXiv:1802.07206].
4.	Desmond, Harry, et al. (författare) The fifth force in the local cosmic web 2019 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 483:1, s. l64-L68 Tidskriftsartikel (refereegranskat)abstract Extensions of the standard models of particle physics and cosmology often lead to long-range fifth forces with properties dependent on gravitational environment. Fifth forces on astrophysical scales are best studied in the cosmic web where perturbation theory breaks down. We present constraints on chameleon-and symmetron-screened fifth forces with Yukawa coupling and megaparsec range - as well as unscreened fifth forces with differential coupling to galactic mass components - by searching for the displacements they predict between galaxies' stars and gas. Taking data from the Alfalfa HI survey, identifying galaxies' gravitational environments with the maps of Desmond et al. and forward modelling with a Bayesian likelihood framework, we set upper bounds on fifth-force strength relative to Newtonian gravity from similar to few x 10(-4) (1 sigma) for range lambda(C) = 50 Mpc, to similar to 0.1 for lambda(C) = 500 kpc. In f(R) gravity this requires f(R0) <= few x 10(-8). The analogous bounds without screening are similar to few x 10(-4) and few x 10(-3). These are the tightest and among the only fifth-force constraints on galaxy scales. We show how our results may be strengthened with future survey data and identify the key features of an observational programme for furthering fifth-force tests beyond the Solar system.
5.	Elbers, Willem, et al. (författare) Where shadows lie : reconstruction of anisotropies in the neutrino sky 2023 Ingår i: Journal of Cosmology and Astroparticle Physics. - 1475-7516. ; :10 Tidskriftsartikel (refereegranskat)abstract The Cosmic Neutrino Background (CNB) encodes a wealth of information, but has not yet been observed directly. To determine the prospects of detection and to study its information content, we reconstruct the phase-space distribution of local relic neutrinos from the three-dimensional distribution of matter within 200 h-1 Mpc of the Milky Way. Our analysis relies on constrained realization simulations and forward modelling of the 2M++ galaxy catalogue. We find that the angular distribution of neutrinos is anti-correlated with the projected matter density, due to the capture and deflection of neutrinos by massive structures along the line of sight. Of relevance to tritium capture experiments, we find that the gravitational clustering effect of the large-scale structure on the local number density of neutrinos is more important than that of the Milky Way for neutrino masses less than 0.1 eV. Nevertheless, we predict that the density of relic neutrinos is close to the cosmic average, with a suppression or enhancement over the mean of (-0.3%, +7%, +27%) for masses of (0.01, 0.05, 0.1) eV. This implies no more than a marginal increase in the event rate for tritium capture experiments like PTOLEMY. We also predict that the CNB and CMB rest frames coincide for 0.01 eV neutrinos, but that neutrino velocities are significantly perturbed for masses larger than 0.05 eV. Regardless of mass, we find that the angle between the neutrino dipole and the ecliptic plane is small, implying a near-maximal annual modulation in the bulk velocity. Along with this paper, we publicly release our simulation data, comprising more than 100 simulations for six different neutrino masses.
6.	Elsner, Franz, et al. (författare) Cosmology inference from a biased density field using the EFT-based likelihood 2020 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :1 Tidskriftsartikel (refereegranskat)abstract The effective-field-theory (EFT) approach to the clustering of galaxies and other biased tracers allows for an isolation of the cosmological information that is protected by symmetries, in particular the equivalence principle, and thus is robust to the complicated dynamics of dark matter, gas, and stars on small scales. All existing implementations proceed by making predictions for the lowest-order n-point functions of biased tracers, as well as their covariance, and comparing with measurements. Recently, we presented an EFT-based expression for the conditional probability of the density field of a biased tracer given the matter density field, which in principle uses information from arbitrarily high order n-point functions. Here, we report results based on this likelihood by applying it to halo catalogs in real space, specifically an inference of the power spectrum normalization sigma(8). We include bias terms up to second order as well as the leading higher-derivative term. For a cutoff value of Lambda = 0.1 hMpc(-1), we recover the ground-truth value of sigma(8) to within 95% CL for different halo samples and redshifts. We discuss possible sources for the remaining systematic bias in sigma(8) as well as future developments.
7.	Hutschenreuter, Sebastian, et al. (författare) The primordial magnetic field in our cosmic backyard 2018 Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 35:15 Tidskriftsartikel (refereegranskat)abstract We reconstruct for the first time the three dimensional structure of magnetic fields on cosmological scales, which were seeded by density perturbations during the radiation dominated epoch of the Universe and later on were evolved by structure formation. To achieve this goal, we rely on three dimensional initial density fields inferred from the 2M++ galaxy compilation via the Bayesian BORG algorithm. Using those, we estimate the magnetogenesis by the so called Harrison mechanism. This effect produced magnetic fields exploiting the different photon drag on electrons and ions in vortical motions, which are exited due to second order perturbation effects in the Early Universe. Subsequently we study the evolution of these seed fields through the non- linear cosmic structure formation by virtue of a magneto-hydrodynamics simulation to obtain a 3D estimate for the structure of this primordial magnetic field component today. At recombination we obtain large scale magnetic field strengths around 10(-23) G, with a power spectrum peaking at about 2 Mpc(-1) h in comoving scales. At present we expect this evolved primordial field to have strengths above approximate to 10(-27) G and approximate to 10(-29) G in clusters of galaxies and voids, respectively. We also calculate the corresponding Faraday rotation measure map and show the magnetic field morphology and strength for specific objects of the Local Universe. These results provide a reliable lower limit on the primordial component of the magnetic fields in these structures.
8.	Johansson Andrews, Adam, 1992-, et al. (författare) Bayesian field-level inference of primordial non-Gaussianity using next-generation galaxy surveys 2023 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 520:4, s. 5746-5763 Tidskriftsartikel (refereegranskat)abstract Detecting and measuring a non-Gaussian signature of primordial origin in the density field is a major science goal of next-generation galaxy surveys. The signal will permit us to determine primordial-physics processes and constrain models of cosmic inflation. While traditional approaches use a limited set of statistical summaries of the galaxy distribution to constrain primordial non-Gaussianity, we present a field-level approach by Bayesian forward modelling the entire three-dimensional galaxy survey. Since our method includes the entire cosmic field in the analysis, it can naturally and fully self-consistently exploit all available information in the large-scale structure, to extract information on the local non-Gaussianity parameter, fnl. Examples include higher order statistics through correlation functions, peculiar velocity fields through redshift-space distortions, and scale-dependent galaxy bias. To illustrate the feasibility of field-level primordial non-Gaussianity inference, we present our approach using a first-order Lagrangian perturbation theory model, approximating structure growth at sufficiently large scales. We demonstrate the performance of our approach through various tests with self-consistent mock galaxy data emulating relevant features of the SDSS-III/BOSS-like survey, and additional tests with a Stage IV mock data set. These tests reveal that the method infers unbiased values of fnl by accurately handling survey geometries, noise, and unknown galaxy biases. We demonstrate that our method can achieve constraints of σfnl≈8.78 for SDSS-III/BOSS-like data, indicating potential improvements of a factor ∼2.5 over current published constraints. We perform resolution studies on scales larger than ∼16h−1 Mpc showing the promise of significant constraints with next-generation surveys. Furthermore, the results demonstrate that our method can consistently marginalize all nuisance parameters of the data model. The method further provides an inference of the three-dimensional primordial density field, providing opportunities to explore additional signatures of primordial physics. This first demonstration of a field-level inference pipeline demonstrates a promising complementary path forward for analysing next-generation surveys.
9.	Kostić, Andrija, et al. (författare) Optimal machine-driven acquisition of future cosmological data 2022 Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 657 Tidskriftsartikel (refereegranskat)abstract We present a set of maps classifying regions of the sky according to their information gain potential as quantified by Fisher information. These maps can guide the optimal retrieval of relevant physical information with targeted cosmological searches. Specifically, we calculated the response of observed cosmic structures to perturbative changes in the cosmological model and we charted their respective contributions to Fisher information. Our physical forward-modeling machinery transcends the limitations of contemporary analyses based on statistical summaries to yield detailed characterizations of individual 3D structures. We demonstrate this advantage using galaxy counts data and we showcase the potential of our approach by studying the information gain of the Coma cluster. We find that regions in the vicinity of the filaments and cluster core, where mass accretion ensues from gravitational infall, are the most informative with regard to our physical model of structure formation in the Universe. Hence, collecting data in those regions would be most optimal for testing our model predictions. The results presented in this work are the first of their kind to elucidate the inhomogeneous distribution of cosmological information in the Universe. This study paves a new way forward for the performance of efficient targeted searches for the fundamental physics of the Universe, where search strategies are progressively refined with new cosmological data sets within an active learning framework.
10.	McAlpine, Stuart, et al. (författare) SIBELIUS-DARK : a galaxy catalogue of the local volume from a constrained realization simulation 2022 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 512:4, s. 5823-5847 Tidskriftsartikel (refereegranskat)abstract We present SIBELIUS-DARK, a constrained realization simulation of the local volume to a distance of 200 Mpc from the Milky Way. SIBELIUS-DARK is the first study of the ‘Simulations Beyond The Local Universe’ (SIBELIUS) project, which has the goal of embedding a model Local Group-like system within the correct cosmic environment. The simulation is dark-matter-only, with the galaxy population calculated using the semi-analytic model of galaxy formation, GALFORM. We demonstrate that the large-scale structure that emerges from the SIBELIUS constrained initial conditions matches well the observational data. The inferred galaxy population of SIBELIUS-DARK also match well the observational data, both statistically for the whole volume and on an object-by-object basis for the most massive clusters. For example, the K-band number counts across the whole sky, and when divided between the northern and southern Galactic hemispheres, are well reproduced by SIBELIUS-DARK. We find that the local volume is somewhat unusual in the wider context of ΛCDM: it contains an abnormally high number of supermassive clusters, as well as an overall large-scale underdensity at the level of ≈5 per cent relative to the cosmic mean. However, whilst rare, the extent of these peculiarities does not significantly challenge the ΛCDM model. SIBELIUS-DARK is the most comprehensive constrained realization simulation of the local volume to date, and with this paper we publicly release the halo and galaxy catalogues at z = 0, which we hope will be useful to the wider astronomy community.
11.	Mukherjee, Suvodip, et al. (författare) Velocity correction for Hubble constant measurements from standard sirens 2021 Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 646 Tidskriftsartikel (refereegranskat)abstract Gravitational wave (GW) sources are an excellent probe of the luminosity distance and o ffer a novel measure of the Hubble constant, H-0. This estimation of H-0 from standard sirens requires an accurate estimation of the cosmological redshift of the host galaxy of the GW source after correcting for its peculiar velocity. The absence of an accurate peculiar velocity correction a ffects both the precision and accuracy of the measurement of H-0, particularly for nearby sources. Here, we propose a framework to incorporate such a peculiar velocity correction for GW sources. A first implementation of our method to the event GW170817, combined with observations taken with Very Large Baseline Interferometry (VLBI), leads to a revised value of H-0 = 68.3(-4.5)(+4.6) km s(-1) Mpc(-1). While this revision is minor, it demonstrates that our method makes it possible to obtain unbiased and accurate measurements of H-0 at the precision required for the standard siren cosmology.
12.	Nguyen, Nhat-Minh, et al. (författare) Impacts of the physical data model on the forward inference of initial conditions from biased tracers 2021 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :3 Tidskriftsartikel (refereegranskat)abstract We investigate the impact of each ingredient in the employed physical data model on the Bayesian forward inference of initial conditions from biased tracers at the field level. Specifically, we use dark matter halos in a given cosmological simulation volume as tracers of the underlying matter density field. We study the effect of tracer density, grid resolution, gravity model, bias model and likelihood on the inferred initial conditions. We find that the cross-correlation coefficient between true and inferred phases reacts weakly to all ingredients above, and is well predicted by the theoretical expectation derived from a Gaussian model on a broad range of scales. The bias in the amplitude of the inferred initial conditions, on the other hand, depends strongly on the bias model and the likelihood. We conclude that the bias model and likelihood hold the key to an unbiased cosmological inference. Together they must keep the systematics - which arise from the sub-grid physics that are marginalized over - under control in order to obtain an unbiased inference.
13.	Nhat-Minh, Nguyen, et al. (författare) Taking measurements of the kinematic Sunyaev-Zel'dovich effect forward : including uncertainties from velocity reconstruction with forward modeling 2020 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :12 Tidskriftsartikel (refereegranskat)abstract We measure the kinematic Sunyaev-Zel'dovich (kSZ) effect, imprinted by maxBCG clusters, on the Planck SMICA map of the Cosmic Microwave Background (CMB). Our measurement, for the first time, directly accounts for uncertainties in the velocity reconstruction step through the process of Bayesian forward modeling. We show that this often neglected uncertainty budget typically increases the final uncertainty on the measured kSZ signal amplitude by similar or equal to 15% at cluster scales. We observe evidence for the kSZ effect, at a significance of similar or equal to 2 sigma. Our analysis, when applied to future higher-resolution CMB data, together with minor improvements in map-filtering and signal-modeling methods, should yield both significant and unbiased measurements of the kSZ signal, which can then be used to probe and constrain the baryonic content of galaxy clusters and galaxy groups.
14.	Porqueres, Natalia, et al. (författare) A hierarchical field-level inference approach to reconstruction from sparse Lyman-α forest data 2020 Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 642 Tidskriftsartikel (refereegranskat)abstract We address the problem of inferring the three-dimensional matter distribution from a sparse set of one-dimensional quasar absorption spectra of the Lyman-alpha forest. Using a Bayesian forward modelling approach, we focus on extending the dynamical model to a fully self-consistent hierarchical field-level prediction of redshift-space quasar absorption sightlines. Our field-level approach rests on a recently developed semiclassical analogue to Lagrangian perturbation theory (LPT), which improves over noise problems and interpolation requirements of LPT. It furthermore allows for a manifestly conservative mapping of the optical depth to redshift space. In addition, this new dynamical model naturally introduces a coarse-graining scale, which we exploited to accelerate the Markov chain Monte-Carlo (MCMC) sampler using simulated annealing. By gradually reducing the effective temperature of the forward model, we were able to allow it to first converge on large spatial scales before the sampler became sensitive to the increasingly larger space of smaller scales. We demonstrate the advantages, in terms of speed and noise properties, of this field-level approach over using LPT as a forward model, and, using mock data, we validated its performance to reconstruct three-dimensional primordial perturbations and matter distribution from sparse quasar sightlines.
15.	Porqueres, Natalia, et al. (författare) Bayesian forward modelling of cosmic shear data 2021 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 502:2, s. 3035-3044 Tidskriftsartikel (refereegranskat)abstract We present a Bayesian hierarchical modelling approach to infer the cosmic matter density field, and the lensing and the matter power spectra, from cosmic shear data. This method uses a physical model of cosmic structure formation to infer physically plausible cosmic structures, which accounts for the non-Gaussian features of the gravitationally evolved matter distribution and light-cone effects. We test and validate our framework with realistic simulated shear data, demonstrating that the method recovers the unbiased matter distribution and the correct lensing and matter power spectrum. While the cosmology is fixed in this test, and the method employs a prior power spectrum, we demonstrate that the lensing results are sensitive to the true power spectrum when this differs from the prior. In this case, the density field samples are generated with a power spectrum that deviates from the prior, and the method recovers the true lensing power spectrum. The method also recovers the matter power spectrum across the sky, but as currently implemented, it cannot determine the radial power since isotropy is not imposed. In summary, our method provides physically plausible inference of the dark matter distribution from cosmic shear data, allowing us to extract information beyond the two-point statistics and exploiting the full information content of the cosmological fields.
16.	Porqueres, Natalia, et al. (författare) Explicit Bayesian treatment of unknown foreground contaminations in galaxy surveys 2019 Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 624 Tidskriftsartikel (refereegranskat)abstract The treatment of unknown foreground contaminations will be one of the major challenges for galaxy clustering analyses of coming decadal surveys. These data contaminations introduce erroneous large-scale effects in recovered power spectra and inferred dark matter density fields. In this work, we present an effective solution to this problem in the form of a robust likelihood designed to account for effects due to unknown foreground and target contaminations. Conceptually, this robust likelihood marginalizes over the unknown large-scale contamination amplitudes. We showcase the effectiveness of this novel likelihood via an application to a mock SDSS-III data set subject to dust extinction contamination. In order to illustrate the performance of our proposed likelihood, we infer the underlying dark-matter density field and reconstruct the matter power spectrum, being maximally agnostic about the foregrounds. The results are compared to those of an analysis with a standard Poissonian likelihood, as typically used in modern large-scale structure analyses. While the standard Poissonian analysis yields excessive power for large-scale modes and introduces an overall bias in the power spectrum, our likelihood provides unbiased estimates of the matter power spectrum over the entire range of Fourier modes considered in this work. Further, we demonstrate that our approach accurately accounts for and corrects the effects of unknown foreground contaminations when inferring three-dimensional density fields. Robust likelihood approaches, as presented in this work, will be crucial to control unknown systematic error and maximize the outcome of the decadal surveys.
17.	Porqueres, Natalia, et al. (författare) Inferring high-redshift large-scale structure dynamics from the Lyman-alpha forest 2019 Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 630 Tidskriftsartikel (refereegranskat)abstract One of the major science goals over the coming decade is to test fundamental physics with probes of the cosmic large-scale structure out to high redshift. Here we present a fully Bayesian approach to infer the three-dimensional cosmic matter distribution and its dynamics at z > 2 from observations of the Lyman-alpha forest. We demonstrate that the method recovers the unbiased mass distribution and the correct matter power spectrum at all scales. Our method infers the three-dimensional density field from a set of one-dimensional spectra, interpolating the information between the lines of sight. We show that our algorithm provides unbiased mass profiles of clusters, becoming an alternative for estimating cluster masses complementary to weak lensing or X-ray observations. The algorithm employs a Hamiltonian Monte Carlo method to generate realizations of initial and evolved density fields and the three-dimensional large-scale flow, revealing the cosmic dynamics at high redshift. The method correctly handles multi-modal parameter distributions, which allow constraining the physics of the intergalactic medium with high accuracy. We performed several tests using realistic simulated quasar spectra to test and validate our method. Our results show that detailed and physically plausible inference of three-dimensional large-scale structures at high redshift has become feasible.
18.	Porqueres, Natalia, et al. (författare) Lifting weak lensing degeneracies with a field-based likelihood 2021 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 509:3, s. 3194-3202 Tidskriftsartikel (refereegranskat)abstract We present a field-based approach to the analysis of cosmic shear data to infer jointly cosmological parameters and the dark matter distribution. This forward modelling approach samples the cosmological parameters and the initial matter fluctuations, using a physical gravity model to link the primordial fluctuations to the non-linear matter distribution. Cosmological parameters are sampled and updated consistently through the forward model, varying (1) the initial matter power spectrum, (2) the geometry through the distance-redshift relationship, and (3) the growth of structure and light-cone effects. Our approach extracts more information from the data than methods based on two-point statistics. We find that this field-based approach lifts the strong degeneracy between the cosmological matter density, Ωm, and the fluctuation amplitude, σ8, providing tight constraints on these parameters from weak lensing data alone. In the simulated four-bin tomographic experiment we consider, the field-based likelihood yields marginal uncertainties on σ8 and Ωm that are, respectively, a factor of 3 and 5 smaller than those from a two-point power spectrum analysis applied to the same underlying data.
19.	Prideaux-Ghee, James, et al. (författare) Field-based physical inference from peculiar velocity tracers 2022 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 518:3, s. 4191-4213 Tidskriftsartikel (refereegranskat)abstract We present a proof-of-concept Bayesian hierarchical modelling approach to reconstruct the initial cosmic matter density field constrained by peculiar velocity observations. Using a model for the gravitational evolution of dark matter to connect the initial conditions to late-time observations, it reconstructs the late-time density and velocity fields as natural byproducts. We implement this field-based physical inference approach by adapting the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm, which explores the high-dimensional posterior through the use of Hamiltonian Monte Carlo sampling. We test the self-consistency of the method using random sets of tracers, and assess its accuracy in a more complex scenario where peculiar velocity tracers are mock haloes drawn from GADGET2 N-body simulations. We find that our framework self-consistently infers the initial conditions, density and velocity fields, and shows some robustness to model mis-specification. Compared with the approach of constrained Gaussian random fields/Wiener filtering, the hierarchical model produces more accurate final density and velocity field reconstructions. It also allows us to constrain the initial conditions by peculiar velocity observations, complementing in this aspect other field-based approaches based on alternative cosmological observables such as galaxy clustering or weak lensing.
20.	Sawala, Till, et al. (författare) Distinct distributions of elliptical and disk galaxies across the Local Supercluster as a ΛCDM prediction 2024 Ingår i: Nature Astronomy. - 2397-3366. ; 8:2, s. 247-255 Tidskriftsartikel (refereegranskat)abstract Galaxies of different types are not equally distributed in the Local Universe. In particular, the supergalactic plane is prominent among the brightest ellipticals, but inconspicuous among the brightest disk galaxies. This striking difference provides a unique test for our understanding of galaxy and structure formation. Here we use the SIBELIUS DARK constrained simulation to confront the predictions of the standard Lambda Cold Dark Matter (ΛCDM) model and standard galaxy formation theory with these observations. We find that SIBELIUS DARK reproduces the spatial distributions of disks and ellipticals and, in particular, the observed excess of massive ellipticals near the supergalactic equator. We show that this follows directly from the local large-scale structure and from the standard galaxy formation paradigm, wherein disk galaxies evolve mostly in isolation, while giant ellipticals congregate in the massive clusters that define the supergalactic plane. Rather than being anomalous as earlier works have suggested, the distributions of giant ellipticals and disks in the Local Universe and in relation to the supergalactic plane are key predictions of the ΛCDM model.
21.	Sawala, Till, et al. (författare) Setting the stage : structures from Gaussian random fields 2021 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 501:4, s. 4759-4776 Tidskriftsartikel (refereegranskat)abstract We study structure formation in a set of cosmological simulations to uncover the scales in the initial density field that gave rise to the formation of present-day structures. Our simulations share a common primordial power spectrum (here Lambda cold dark matter, Lambda CDM), but the introduction of hierarchical variations of the phase information allows us to systematically study the scales that determine the formation of structure at later times. We consider the variance in z = 0 statistics such as the matter power spectrum and halo mass function. We also define a criterion for the existence of individual haloes across simulations, and determine what scales in the initial density field contain sufficient information for the non-linear formation of unique haloes. We study how the characteristics of individual haloes such as the mass and concentration, as well as the position and velocity, are affected by variations on different scales, and give scaling relations for haloes of different mass. Finally, we use the example of a cluster-mass halo to show how our hierarchical parametrization of the initial density field can be used to create variants of particular objects. With properties such as mass, concentration, kinematics, and substructure of haloes set on distinct and well-determined scales, and its unique ability to introduce variations localized in real space, our method is a powerful tool to study structure formation in cosmological simulations.
22.	Sawala, Till, et al. (författare) The Milky Way’s plane of satellites is consistent with ΛCDM 2023 Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 7:4, s. 481-491 Tidskriftsartikel (refereegranskat)abstract The Milky Way is surrounded by 11 ‘classical’ satellite galaxies in a remarkable configuration: a thin plane that is possibly rotationally supported. Such a structure is thought to be highly unlikely to arise in the standard (ΛCDM) cosmological model (Λ cold dark matter model, where Λ is the cosmological constant). While other apparent discrepancies between predictions and observations of Milky Way satellite galaxies may be explained either through baryonic effects or by invoking alternative forms of dark matter particles, there is no known mechanism for making rotating satellite planes within the dispersion-supported dark matter haloes predicted to surround galaxies such as the Milky Way. This is the so-called ‘plane of satellites problem’, which challenges not only the ΛCDM model but the entire concept of dark matter. Here we show that the reportedly exceptional anisotropy of the Milky Way satellites is explained, in large part, by their lopsided radial distribution combined with the temporary conjunction of the two most distant satellites, Leo I and Leo II. Using Gaia proper motions, we show that the orbital pole alignment is much more common than previously reported, and reveal the plane of satellites to be transient rather than rotationally supported. Comparing with new simulations, where such short-lived planes are common, we find the Milky Way satellites to be compatible with standard model expectations.
23.	Sawala, Till, et al. (författare) The SIBELIUS Project : E Pluribus Unum 2022 Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 509:1, s. 1432-1446 Tidskriftsartikel (refereegranskat)abstract We introduce 'Simulations Beyond The Local Universe' (SIBELIUS) that connect the Local Group (LG) to its cosmic environment. We show that introducing hierarchical small-scale perturbations to a density field constrained on large scales by observations provides an efficient way to explore the sample space of LG analogues. From more than 60 000 simulations, we identify a hierarchy of LG characteristics emanating from different scales: the total mass, orientation, orbital energy, and the angular momentum are largely determined by modes above lambda = 1.6 comoving Mpc (cMpc) in the primordial density field. Smaller scale variations are mostly manifest as perturbations to the MW-M31 orbit, and we find that the observables commonly used to describe the LG - the MW M31 separation and radial velocity - are transient and depend on specifying scales down to 0.2 cMpc in the primordial density field. We further find that the presence of M33/LMC analogues significantly affects the MW-M31 orbit and its sensitivity to small-scale perturbations. We construct initial conditions that lead to the formation of an LG whose primary observables precisely match the current observations.
24.	Schmidt, Fabian, et al. (författare) A rigorous EFT-based forward model for large-scale structure 2019 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :1 Tidskriftsartikel (refereegranskat)abstract Conventional approaches to cosmology inference from galaxy redshift surveys are based on n-point functions, which are under rigorous perturbative control on sufficiently large scales. Here, we present an alternative approach, which employs a likelihood at the level of the galaxy density field. By integrating out small-scale modes based on effective-field theory arguments, we prove that this likelihood is under perturbative control if certain specific conditions are met. We further show that the information captured by this likelihood is equivalent to the combination of the next-to-leading order galaxy power spectrum, leading-order bispectrum, and BAO reconstruction. Combined with MCMC sampling and MAP optimization techniques, our results allow for fully Bayesian cosmology inference from large-scale structure that is under perturbative control. We illustrate this via a first demonstration of unbiased cosmology inference from nonlinear large-scale structure using this likelihood. In particular, we show unbiased estimates of the power spectrum normalization sigma(8) from a catalog of simulated dark matter halos, where nonlinear information is crucial in breaking the b(1) - sigma(8) degeneracy.
25.	Schmidt, Fabian, et al. (författare) Unbiased cosmology inference from biased tracers using the EFT likelihood 2020 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :11 Tidskriftsartikel (refereegranskat)abstract We present updates on the cosmology inference using the effective field theory (EFT) likelihood presented previously in Schmidt et al., 2018, Elsner et al., 2019 [1, 2]. Specifically, we add a cutoff to the initial conditions that serve as starting point for the matter forward model. We show that this cutoff, which was not employed in any previous related work, is important to regularize loop integrals that otherwise involve small-scale, non-perturbative modes. We then present results on the inferred value of the linear power spectrum normalization sigma(8) from rest-frame halo catalogs using both second- and third-order bias expansions, imposing uniform priors on all bias parameters. Due to the perfect bias-sigma(8) degeneracy at linear order, constraints on sigma(8) rely entirely on nonlinear information. The results show the expected convergence behavior when lowering the cutoff in wavenumber, A. When including modes up to k <= Lambda = 0.1 hMpc(-1) in the second-order case, sigma(8) is recovered to within less than or similar to 6% for a range of halo masses and redshifts. The systematic bias shrinks to 4% or less for the third-order bias expansion on the same range of scales. Together with additional evidence we provide, this shows that the residual mismatch in sigma(8) can be attributed to higher-order bias contributions. We conclude that the EFT likelihood is able to infer unbiased cosmological constraints, within expected theoretical systematic errors, from physical biased tracers on quasilinear scales.
26.	Stopyra, Stephen, et al. (författare) An antihalo void catalogue of the Local Super-Volume 2024 Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 531:2, s. 2213-2222 Tidskriftsartikel (refereegranskat)abstract We construct an antihalo void catalogue of 150 voids with radii ?>10ℎ−1Mpc in the Local Super-Volume (⁠<135ℎ−1Mpc from the Milky Way), using posterior resimulation of initial conditions inferred by field-level inference with Bayesian Origin Reconstruction from Galaxies (BORG). We describe and make use of a new algorithm for creating a single, unified void catalogue by combining different samples from the posterior. The catalogue is complete out to 135ℎ−1Mpc⁠, with void abundances matching theoretical predictions. Finally, we compute stacked density profiles of those voids which are reliably identified across posterior samples, and show that these are compatible with Λ cold dark matter expectations once environmental selection (e.g. the estimated ∼4 per cent underdensity of the Local Super-Volume) is accounted for.
27.	Stopyra, Stephen, et al. (författare) Towards accurate field-level inference of massive cosmic structures 2023 Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 527:1, s. 1244-1256 Tidskriftsartikel (refereegranskat)abstract We investigate the accuracy requirements for field-level inference of cluster and void masses using data from galaxy surveys. We introduce a two-step framework that takes advantage of the fact that cluster masses are determined by flows on larger scales than the clusters themselves. First, we determine the integration accuracy required to perform field-level inference of cosmic initial conditions on these large scales by fitting to late-time galaxy counts using the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. A 20-step COLA integrator is able to accurately describe the density field surrounding the most massive clusters in the local super-volume (⁠<135ℎ−1Mpc⁠), but does not by itself lead to converged virial mass estimates. Therefore, we carry out ‘posterior resimulations’, using full N-body dynamics while sampling from the inferred initial conditions, and thereby obtain estimates of masses for nearby massive clusters. We show that these are in broad agreement with existing estimates, and find that mass functions in the local super-volume are compatible with ΛCDM.
28.	Tsaprazi, Eleni, et al. (författare) Field-level inference of galaxy intrinsic alignment from the SDSS-III BOSS survey Annan publikation (övrigt vetenskapligt/konstnärligt)
29.	Tsaprazi, Eleni, et al. (författare) Field-level inference of galaxy intrinsic alignment from the SDSS-III BOSS survey 2022 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2022:08 Tidskriftsartikel (refereegranskat)abstract As a large-scale overdensity collapses, it affects the orientation and shape of galaxies that form, by exerting tidal shear along their axes. Therefore, the shapes of elliptical galaxies align with the tidal field of cosmic structures. This intrinsic alignment provides insights into galaxy formation and the primordial universe, complements late-time cosmological probes and constitutes a significant systematic effect for weak gravitational lensing observations. In the present study, we provide constraints on the linear alignment model using a fully Bayesian field-level approach, using galaxy shape measurements from the SDSS-III BOSS LOWZ sample and three-dimensional tidal fields constrained with the LOWZ and CMASS galaxy samples of the SDSS-III BOSS survey. We find 4σ evidence of intrinsic alignment, with an amplitude of AI = 2.9 ± 0.7 at 20 Mpch.
30.	Tsaprazi, Eleni, et al. (författare) Higher-order statistics of the large-scale structure from photometric redshifts Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract The large-scale structure is a major source of cosmological information. However, next-generation photometric galaxy surveys will only provide a distorted view of cosmic structures due to large redshift uncertainties. To address the need for accurate reconstructions of the large-scale structure in presence of photometric uncertainties, we present a framework that constrains the three-dimensional dark matter density jointly with galaxy photometric redshift probability density functions (PDFs), exploiting information from galaxy clustering. Our forward model provides Markov Chain Monte Carlo realizations of the primordial and present-day dark matter density, inferred jointly from data. Our method goes beyond 2-point statistics via field-level inference. It accounts for all observational uncertainties and the survey geometry. We showcase our method using mock catalogs that emulate next-generation surveys with a worst-case redshift uncertainty, equivalent to ∼300 Mpc. On scales 150 Mpc, we improve the cross-correlation of the photometric galaxy positions with the ground truth from 28% to 86%. The improvement is significant down to 13 Mpc. On scales 150 Mpc, we achieve a cross-correlation of 80−90% with the ground truth for the dark matter density, radial peculiar velocities, tidal shear and gravitational potential.
31.	Tsaprazi, Eleni, et al. (författare) Higher-order statistics of the large-scale structure from photometric redshifts Annan publikation (övrigt vetenskapligt/konstnärligt)

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