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Sökning: WFRF:(Jasche Jens)

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1.
  • Jasche, Jens, et al. (författare)
  • Constraints on equivalence principle violation from gamma ray bursts
  • 2021
  • Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 104:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Theories of gravity that obey the weak equivalence principle have the same parametrized post-Newtonian parameter gamma for all particles at all energies. The large Shapiro time delays of extragalactic sources allow us to put tight constraints on differences in gamma between photons of different frequencies from spectral lag data, since a nonzero Delta gamma would result in a frequency-dependent arrival time. The majority of previous constraints have assumed that the Shapiro time delay is dominated by a few local massive objects, although this is a poor approximation for distant sources. In this work we consider the cosmological context of these sources by developing a source-by-source, Monte Carlo-based forward model for the Shapiro time delays by combining constrained realizations of the local density field using the Bayesian origin reconstruction from galaxies algorithm with unconstrained large-scale modes. Propagating uncertainties in the density field reconstruction and marginalizing over an empirical model describing other contributions to the time delay, we use spectral lag data of gamma ray bursts from the BATSE satellite to constrain Delta gamma < 2.1 x 10(-15) at 1 sigma confidence between photon energies of 25 keV and 325 keV.
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2.
  • Ballardini, M., et al. (författare)
  • Euclid : The search for primordial features
  • 2024
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
  • Tidskriftsartikel (refereegranskat)abstract
    • Primordial features, in particular oscillatory signals, imprinted in the primordial power spectrum of density perturbations represent a clear window of opportunity for detecting new physics at high-energy scales. Future spectroscopic and photometric measurements from the Euclid space mission will provide unique constraints on the primordial power spectrum, thanks to the redshift coverage and high-accuracy measurement of nonlinear scales, thus allowing us to investigate deviations from the standard power-law primordial power spectrum. We consider two models with primordial undamped oscillations superimposed on the matter power spectrum described by 1 + ?X sin (ωXΞX + 2 πϕX), one linearly spaced in k space with Ξlin ≡ k/k* where k* = 0.05 Mpc−1 and the other logarithmically spaced in k space with Ξlog ≡ ln(k/k*). We note that ?X is the amplitude of the primordial feature, ωX is the dimensionless frequency, and ϕX is the normalised phase, where X = {lin, log}. We provide forecasts from spectroscopic and photometric primary Euclid probes on the standard cosmological parameters Ωm, 0, Ωb, 0, h, ns, and σ8, and the primordial feature parameters ?X, ωX, and ϕX. We focus on the uncertainties of the primordial feature amplitude ?X and on the capability of Euclid to detect primordial features at a given frequency. We also study a nonlinear density reconstruction method in order to retrieve the oscillatory signals in the primordial power spectrum, which are damped on small scales in the late-time Universe due to cosmic structure formation. Finally, we also include the expected measurements from Euclid’s galaxy-clustering bispectrum and from observations of the cosmic microwave background (CMB). We forecast uncertainties in estimated values of the cosmological parameters with a Fisher matrix method applied to spectroscopic galaxy clustering (GCsp), weak lensing (WL), photometric galaxy clustering (GCph), the cross correlation (XC) between GCph and WL, the spectroscopic galaxy clustering bispectrum, the CMB temperature and E-mode polarisation, the temperature-polarisation cross correlation, and CMB weak lensing. We consider two sets of specifications for the Euclid probes (pessimistic and optimistic) and three different CMB experiment configurations, that is, Planck, Simons Observatory (SO), and CMB Stage-4 (CMB-S4). We find the following percentage relative errors in the feature amplitude with Euclid primary probes: for the linear (logarithmic) feature model, with a fiducial value of ?X = 0.01, ωX = 10, and ϕX = 0: 21% (22%) in the pessimistic settings and 18% (18%) in the optimistic settings at a 68.3% confidence level (CL) using GCsp+WL+GCph+XC. While the uncertainties on the feature amplitude are strongly dependent on the frequency value when single Euclid probes are considered, we find robust constraints on ?X from the combination of spectroscopic and photometric measurements over the frequency range of (1,  102.1). Due to the inclusion of numerical reconstruction, the GCsp bispectrum, SO-like CMB reduces the uncertainty on the primordial feature amplitude by 32%–48%, 50%–65%, and 15%–50%, respectively. Combining all the sources of information explored expected from Euclid in combination with the future SO-like CMB experiment, we forecast ?lin ≃ 0.010 ± 0.001 at a 68.3% CL and ?log ≃ 0.010 ± 0.001 for GCsp(PS rec + BS)+WL+GCph+XC+SO-like for both the optimistic and pessimistic settings over the frequency range (1,  102.1).
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3.
  • Bartlett, D. J., et al. (författare)
  • Constraints on dark matter annihilation and decay from the large-scale structure of the nearby Universe
  • 2022
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 106:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Decaying or annihilating dark matter particles could be detected through gamma-ray emission from the species they decay or annihilate into. This is usually done by modeling the flux from specific dark matter–rich objects such as the Milky Way halo, Local Group dwarfs, and nearby groups. However, these objects are expected to have significant emission from baryonic processes as well, and the analyses discard gamma-ray data over most of the sky. Here we construct full-sky templates for gamma-ray flux from the large-scale structure within ∼200  Mpc by means of a suite of constrained N-body simulations (csiborg) produced using the Bayesian Origin Reconstruction from Galaxies algorithm. Marginalizing over uncertainties in this reconstruction, small-scale structure, and parameters describing astrophysical contributions to the observed gamma-ray sky, we compare to observations from the Fermi Large Area Telescope to constrain dark matter annihilation cross sections and decay rates through a Markov chain Monte Carlo analysis. We rule out the thermal relic cross section for s-wave annihilation for all mχ≲7  GeV/c2 at 95% confidence if the annihilation produces gluons or quarks less massive than the bottom quark. We infer a contribution to the gamma-ray sky with the same spatial distribution as dark matter decay at 3.3σ. Although this could be due to dark matter decay via these channels with a decay rate Γ≈6×10−28  s−1, we find that a power-law spectrum of index p=−2.75+0.71−0.46, likely of baryonic origin, is preferred by the data.
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4.
  • Bartlett, D. J., et al. (författare)
  • Constraints on quantum gravity and the photon mass from gamma ray bursts
  • 2021
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 104:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Lorentz invariance violation in quantum gravity (QG) models or a nonzero photon mass, mγ, would lead to an energy-dependent propagation speed for photons, such that photons of different energies from a distant source would arrive at different times, even if they were emitted simultaneously. By developing source-by-source, Monte Carlo-based forward models for such time delays from gamma ray bursts, and marginalizing over empirical noise models describing other contributions to the time delay, we derive constraints on mγ and the QG length scale, ℓQG, using spectral lag data from the BATSE satellite. We find mγ<4.0×10−5 h  eV/c2 and ℓQG<5.3×10−18 h  GeV−1 at 95% confidence, and demonstrate that these constraints are robust to the choice of noise model. The QG constraint is among the tightest from studies which consider multiple gamma ray bursts and the constraint on mγ, although weaker than from using radio data, provides an independent constraint which is less sensitive to the effects of dispersion by electrons.
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5.
  • Boulanger, Francois, et al. (författare)
  • IMAGINE : a comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic rays
  • 2018
  • Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :8
  • Tidskriftsartikel (refereegranskat)abstract
    • In this white paper we introduce the IMAGINE Consortium and its scientific background, goals and structure. The purpose of the consortium is to coordinate and facilitate the efforts of a diverse group of researchers in the broad areas of the interstellar medium, Galactic magnetic fields and cosmic rays, and our overarching goal is to develop more comprehensive insights into the structures and roles of interstellar magnetic fields and their interactions with cosmic rays within the context of Galactic astrophysics. The ongoing rapid development of observational and numerical facilities and techniques has resulted in a widely felt need to advance this subject to a qualitatively higher level of self-consistency, depth and rigour. This can only be achieved by the coordinated efforts of experts in diverse areas of astrophysics involved in observational, theoretical and numerical work. We present our view of the present status of this research area, identify its key unsolved problems and suggest a strategy that will underpin our work. The backbone of the consortium is the Interstellar MAGnetic field INference Engine, a publicly available Bayesian platform that employs robust statistical methods to explore the multi-dimensional likelihood space using any number of modular inputs. This tool will be used by the IMAGINE Consortium to develop an interpretation and modelling framework that provides the method, power and flexibility to interfuse information from a variety of observational, theoretical and numerical lines of evidence into a self-consistent and comprehensive picture of the thermal and non-thermal interstellar media. An important innovation is that a consistent understanding of the phenomena that are directly or indirectly influenced by the Galactic magnetic field, such as the deflection of ultra-high energy cosmic rays or extragalactic backgrounds, is made an integral part of the modelling. The IMAGINE Consortium, which is informal by nature and open to new participants, hereby presents a methodological framework for the modelling and understanding of Galactic magnetic fields that is available to all communities whose research relies on a state of the art solution to this problem.
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6.
  • 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.
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7.
  • Dálya, G., et al. (författare)
  • GLADE + : an extended galaxy catalogue for multimessenger searches with advanced gravitational-wave detectors
  • 2022
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 514:1, s. 1403-1411
  • Tidskriftsartikel (refereegranskat)abstract
    • We present GLADE+, an extended version of the GLADE galaxy catalogue introduced in our previous paper for multimessenger searches with advanced gravitational-wave detectors. GLADE+ combines data from six separate but not independent astronomical catalogues: the GWGC, 2MPZ, 2MASS XSC, HyperLEDA, and WISExSCOSPZ galaxy catalogues, and the SDSS-DR16Q quasar catalogue. To allow corrections of CMB-frame redshifts for peculiar motions, we calculated peculiar velocities along with their standard deviations of all galaxies having B-band magnitude data within redshift z = 0.05 using the ‘Bayesian Origin Reconstruction from Galaxies’ formalism. GLADE+ is complete up to luminosity distance dL=47+4−2 Mpc in terms of the total expected B-band luminosity of galaxies, and contains all of the brightest galaxies giving 90 per cent of the total B-band and K-band luminosity up to dL ≃ 130 Mpc. We include estimations of stellar masses and individual binary neutron star merger rates for galaxies with W1 magnitudes. These parameters can help in ranking galaxies in a given gravitational wave localization volume in terms of their likelihood of being hosts, thereby possibly reducing the number of pointings and total integration time needed to find the electromagnetic counterpart. 
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8.
  • 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.
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9.
  • 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].
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10.
  • 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.
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11.
  • 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.
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12.
  • 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.
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13.
  • Georgiev, Ivelin, 1995- (författare)
  • Studies of the intergalactic medium during the Epoch of Reionization : Understanding observational probes with simulations
  • 2024
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The first billion years of the Universe is a unique era, marked by the formation of the first stars, galaxies, and accreting black holes, which release ionising radiation into the intergalactic medium (IGM). As a result, these luminous sources initiate a period during which the cold and dense IGM, primarily consisting of neutral hydrogen (HI), is heated and ionised. We refer to this era as the Epoch of Reionization (EoR). The EoR is a global phase transition that is not trivial to observe or model computationally. It is a multi-scale event that evolves with time and depends on the nature of the astrophysical processes that govern the formation of stars and galaxies, as well as the fundamental cosmology that defines the properties of the large-scale IGM. While various measurements of cosmic reionization exist, presently they are too few to constrain the entirety of the process. However, observations from the James Webb Space Telescope and the Square Kilometre Array (SKA), among others, will provide new insight into the process. Particularly, the SKA will observe the power spectrum (PS) of the 21 cm signal from the EoR, which originates from the hyperfine transition of neutral hydrogen atoms HI in the IGM that can emit 21 cm photons. In Paper I, we investigate the evolution of the 21 cm PS across the EoR by perturbing the signal and studying its composing terms. We highlight the importance higher-order terms play in shaping the PS on large scales and quantify its evolution. Crucially, we find a characteristic length scale within the 21 cm PS, determined by the mean free path ionising photons travel in the IGM (MFP). Hence, the 21 cm PS has two regimes. We show that the large-scale signal is a biased version of the cosmological density field, and the small-scale PS is determined by the astrophysics of reionization. In Paper II, we use the decomposition of the 21 cm PS and relate it to the PS of the free electron density field. Thus, we analytically connect the 21 cm observable to a probe of the free electron density field. Such a probe is the patchy kinetic Sunyaev-Zel'dovich effect (pkSZ), observed as a foreground to the primary cosmic microwave background temperature anisotropies on small scales. The pkSZ is an integrated probe sensitive to the duration of the EoR and the characteristic size of ionised bubbles. We construct a forecast study of both probes. We show that inferences from 21 cm PS from the SKA can be verified when combined with the pkSZ observation, as each data set is influenced by different systematics. In Paper III, we focus on the modelling of the MFP within large-scale simulations, focusing on the end of reionization (EndEoR). The MFP of ionising photons is inferred from quasar data and depends on several factors. In the post-EoR era, it depends on the distribution and evolution of Lyman Limit systems (LLS), small-scale absorbers that are typically not resolved in large-scale simulations. We investigate the assumptions needed to accurately model the LLS in simulations, and we study their impact on the observables at the EndEoR. We find that LLS modelling has a profound impact on the duration of the final stages of the EoR, the shape of the 21 cm PS as well as other observables of the ionised IGM inferred from quasar spectra, such as the Ultraviolet Background of ionising photons, the effective optical depth of Lyman alpha photons, and the MFP of ionising photons.
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14.
  • Georgiev, Ivelin, 1995- (författare)
  • Understanding the large-scale structure of the the21-cm signal originating from the Epoch of Reionisation
  • 2022
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The first billion years from the beginning of the Universe is the focus of multiple astronomical facilities in the upcoming decade. This unique era is marked by the formation of the first stars and galaxies, which release ionising radiation into the intergalactic medium(IGM). As a result, these sources initiate a period during which the cold and dense IGM, primarily consisting of neutral hydrogen (HI ), is heated and ionised. We refer to this era as the Epoch of Reionisation (EoR). How the EoR transpired hence depends on the properties of these ionising sources, and this forms a vital piece to the puzzle of understanding the early Universe. This licentiate thesis aims to educate the reader on the power spectrum (PS) statistic of the 21-cm signal from HI during the EoR. The PS is a prospective observable by radio interferometers, such as the Low-Frequency Array (LOFAR) and the future Square Kilometre Array (SKA). It is an essential stepping stone in comprehending the dominant physical processes affecting the IGM at a given length scale during the EoR.In Paper I, we analyse the decomposition of the 21-cm PS from Lidz et al. (2007) (eq. 2)and study the evolution of its terms. We conduct our investigation for a set of C 2 -Ray and 21cmFAST simulations with volumes of (714 cMpc)3, concentrating on large-scales (k < 0.3 Mpc−1 ) as the signal-to-noise ratio of observing these scales will be high. We find that the 21-cm PS tracks the PS of neutral hydrogen fluctuations, which itself past a certain scale tracks the matter PS after a global ionisation fraction of x̄HII∼ 0.1. Hence, the 21-cm PS possesses a two-regime form for which the large-scale PS is a biased version of the cosmological density field and the small-scale PS depends on the astrophysics of the EoR. We construct a bias parameter to explore whether the 21-cm PS can be used as a probe of cosmology on large k-scales. We discover a transition feature for both simulations, following the ktrans ≈ 2/λMFP empirical formula. The transition scale between the scale-independent and scale-dependent bias regimes is directly related to the value of the mean free path of ionising photons (λMFP ).
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15.
  • Haverkorn, Marijke, et al. (författare)
  • IMAGINE : Modeling the Galactic Magnetic Field
  • 2019
  • Ingår i: Galaxies. - : MDPI AG. - 2075-4434. ; 7:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The IMAGINE Consortium aims to bring modeling of the magnetic field of the Milky Way to the next level by using Bayesian inference. IMAGINE includes an open-source modular software pipeline that optimizes parameters in a user-defined galactic magnetic field model against various selected observational datasets. Bayesian priors can be added as external probabilistic constraints of the model parameters. These conference proceedings describe the science goals of the IMAGINE consortium, the software pipeline and its inputs, namely observational data sets, galactic magnetic field models, and Bayesian priors.
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16.
  • Holtkamp, Yannick, et al. (författare)
  • Machine-learned correction to ensemble-averaged wave packet dynamics
  • 2023
  • Ingår i: Journal of Chemical Physics. - 0021-9606 .- 1089-7690. ; 159:9
  • Tidskriftsartikel (refereegranskat)abstract
    • For a detailed understanding of many processes in nature involving, for example, energy or electron transfer, the theory of open quantumsystems is of key importance. For larger systems, an accurate description of the underlying quantum dynamics is still a formidable task, and,hence, approaches employing machine learning techniques have been developed to reduce the computational effort of accurate dissipativequantum dynamics. A downside of many previous machine learning methods is that they require expensive numerical training datasets forsystems of the same size as the ones they will be employed on, making them unfeasible to use for larger systems where those calculationsare still too expensive. In this work, we will introduce a new method that is implemented as a machine-learned correction term to the socalled Numerical Integration of Schrödinger Equation (NISE) approach. It is shown that this term can be trained on data from small systemswhere accurate quantum methods are still numerically feasible. Subsequently, the NISE scheme, together with the new machine-learnedcorrection, can be used to determine the dissipative quantum dynamics for larger systems. Furthermore, we show that the newly proposedmachine-learned correction outperforms a previously handcrafted one, which, however, improves the results already considerably. 
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17.
  • 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.
  •  
18.
  • Jasche, Jens, et al. (författare)
  • Physical Bayesian modelling of the non-linear matter distribution : New insights into the nearby universe
  • 2019
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 625
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate analyses of present and next-generation cosmological galaxy surveys require new ways to handle effects of non-linear gravitational structure formation processes in data. To address these needs we present an extension of our previously developed algorithm for Bayesian Origin Reconstruction from Galaxies (BORG) to analyse matter clustering at non-linear scales in observations. This is achieved by incorporating a numerical particle mesh model of gravitational structure formation into our Bayesian inference framework. The algorithm simultaneously infers the three-dimensional primordial matter fluctuations from which present non-linear observations formed and provides reconstructions of velocity fields and structure formation histories. The physical forward modelling approach automatically accounts for the non-Gaussian features in gravitationally evolved matter density fields and addresses the redshift space distortion problem associated with peculiar motions of observed galaxies. Our algorithm employs a hierarchical Bayes approach to jointly account for various observational effects, such as unknown galaxy biases, selection effects, and observational noise. Corresponding parameters of the data model are marginalized out via a sophisticated Markov chain Monte Carlo approach relying on a combination of a multiple block sampling framework and an efficient implementation of a Hamiltonian Monte Carlo sampler. We demonstrate the performance of the method by applying it to the 2M++ galaxy compilation, tracing the matter distribution of the nearby universe. We show accurate and detailed inferences of the three-dimensional non-linear dark matter distribution of the nearby universe. As exemplified in the case of the Coma cluster, our method provides complementary mass estimates that are compatible with those obtained from weak lensing and X-ray observations. For the first time, we also present a reconstruction of the vorticity of the non-linear velocity field from observations. In summary, our method provides plausible and very detailed inferences of the dark matter and velocity fields of our cosmic neighbourhood.
  •  
19.
  • 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.
  •  
20.
  • Johansson Andrews, Adam, 1992- (författare)
  • Reconstructing the Primordial Seeds of Cosmic Structures in Galaxy Surveys
  • 2020
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • One of the most outstanding questions in modern cosmology concerns the physical processes governing the primordial universe and the origin of cosmic structure. These primordial signals appear in a variety of cosmic large-scale structure probes, e.g., in the higher-order statistics of the density field and as a scale-dependent factor in the two-point correlations of the galaxy field. The detection and measurement of such a non-Gaussian primordial signal would generate insights into the shape of the potential of the inflaton field, the hypothetical particle driving cosmic inflation. In the coming years, the next generation of galaxy surveys will commence operation, with the scientific goal of constraining the nonlinearity parameter fnl to the uncertainty required to identify viable inflationary models. However, achieving this goal requires novel statistical data analysis techniques to correctly account for stochastic and systematic uncertainties when measuring these subtle signals from observations.In this licentiate thesis, I present a new approach to measuring primordial non-Gaussianity in galaxy redshift surveys, and demonstrate the proof of concept. State-of-the-art approaches use only a limited set of summary statistics of the density field and cannot account for the full information content of the three-dimensional cosmic structure. To address this problem, I propose a method based on the forward modelling of the initial density field in a Bayesian hierarchical framework. The presented method performs a full-scale Bayesian uncertainty quantification of the posterior distribution of fnl using a Hamiltonian Markov Chain Monte Carlo approach. The method accounts for the gravitational formation of the three-dimensional cosmic structure and thus utilizes the full information content of the three-dimensional dark matter density and velocity field available in the data to constrain primordial non-Gaussianity. In this fashion, the method naturally and fully self-consistently accounts for all stochastic uncertainties and systematic effects associated with selection effects, galaxy biasing, and survey geometries. Notably, multiple probes of primordial non-Gaussianity are jointly incorporated: the 3-point correlation, mass distributions of galaxies, and the scale-dependent bias effect, where this final effect is included into a novel bias model I presented in this work. I apply my method to mock data based on the SDSS-III/BOSS survey, outline tests, and present preliminary results. In addition, I present a variety of scientifically valuable data products, e.g., density field reconstructions and novel maps of primordial curvature fluctuations. Finally, future work is discussed, involving different ways of how to extend the model and additional test data sets on which to apply the method.
  •  
21.
  • 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.
  •  
22.
  • Leclercq, Florent, et al. (författare)
  • Primordial power spectrum and cosmology from black-box galaxy surveys
  • 2019
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 490:3, s. 4237-4253
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a new, likelihood-free approach to inferring the primordial matter power spectrum and cosmological parameters from arbitrarily complex forward models of galaxy surveys where all relevant statistics can be determined from numerical simulations, i.e. black boxes. Our approach, which we call simulator expansion for likelihood-free inference (SELFI), builds upon approximate Bayesian computation using a novel effective likelihood, and upon the linearization of black-box models around an expansion point. Consequently, we obtain simple 'filter equations' for an effective posterior of the primordial power spectrum, and a straightforward scheme for cosmological parameter inference. We demonstrate that the workload is computationally tractable, fixed a priori, and perfectly parallel. As a proof of concept, we apply our framework to a realistic synthetic galaxy survey, with a data model accounting for physical structure formation and incomplete and noisy galaxy observations. In doing so, we show that the use of non-linear numerical models allows the galaxy power spectrum to be safely fitted up to at least k(max) = 0.5 h Mpc(-1), outperforming state-of-the-art backward-modelling techniques by a factor of similar to 5 in the number of modes used. The result is an unbiased inference of the primordial matter power spectrum across the entire range of scales considered, including a high-fidelity reconstruction of baryon acoustic oscillations. It translates into an unbiased and robust inference of cosmological parameters. Our results pave the path towards easy applications of likelihood-free simulation-based inference in cosmology.
  •  
23.
  • Litsa, Aliki, 1994- (författare)
  • Effects of the Higgs field on Inflation and Reheating.
  • 2022
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The model of inflation - a period of accelerated expansion in the very early Universe - was introduced to give solutions to a number of problems encountered in the Standard Big Bang paradigm. Additionally, due to its quantum nature, inflation is able to generate the necessary primordial inhomogeneity “seeds”, which eventually evolve into large-scale structures. The particular primordial inhomogeneities are imprinted on the Cosmic Microwave Background radiation (CMB) as very small deviations (temperature fluctuations) from a perfect blackbody spectrum. If the Standard Model (SM) Higgs is a light spectator field during inflation, it can, also, acquire quantum fluctuations and seed additional, potentially observable, fluctuations. This takes place via an effective breaking of electroweak symmetry at very high energy scales, which results in the reheating process being different in different regions of the Universe. We develop methods for calculating the amplitude, as well as the non-Gaussianity, of such Higgs-induced temperature fluctuations in the CMB. In the case of reheating via resonant inflaton decays to Abelian gauge bosons, we show that the amplitude of the Higgs-induced temperature fluctuations always exceeds the observed value and that, therefore, such decays cannot be the main reheating channel. In the case of reheating via perturbative inflaton decays to SM fermions, we place strong constraints on the relevant SM parameters, using the amplitude of the Higgs temperature fluctuations. By additionally using the associated non-Gaussianity, we are able to strengthen the particular constraints even further. Having made a connection between cosmological observations and SM parameters, such as the Higgs self-coupling, we suggest a way to probe the SM Higgs potential at very high energy scales and constrain New Physics.
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24.
  • 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.
  •  
25.
  • 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.
  •  
26.
  • 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.
  •  
27.
  • 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.
  •  
28.
  • 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.
  •  
29.
  • 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.
  •  
30.
  • 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.
  •  
31.
  • 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.
  •  
32.
  • 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.
  •  
33.
  • 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.
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34.
  • 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.
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35.
  • 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.
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36.
  • 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.
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37.
  • 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.
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38.
  • Setzer, Christian N., 1990- (författare)
  • Modelling and Detecting Kilonovae in the Rubin Observatory Era
  • 2024
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Survey astronomy is a powerful tool for discoveries in astrophysics and cosmology. In the coming years, this field will be revolutionised with the start of the ten-year Legacy Survey of Space and Time (LSST), to be conducted at the Vera C. Rubin Observatory. This survey, with its unique capabilities in temporal sampling, single-image depth and covered sky-area, will explore a new discovery space for astrophysical transients in the Universe. The 2017 discovery of an electromagnetic and gravitational-wave transient presents a unique opportunity to influence the design of the LSST observing strategy for the detection of binary neutron star (BNS) mergers. This will be scientifically beneficial, not only for studies of the astrophysics of these sources, but also for developing new cosmological probes. Given the sensitivity of the Rubin Observatory, it is expected that this instrument will detect these binary neutron star mergers to greater distances than detectable by current and near-term gravitational wave detectors. This presents further opportunities to study the characteristics of the BNS population that will be selected into these surveys. If we understand the underlying BNS merger population and associated electromagnetic emission, it may also be possible to recover the previously undetected counterpart gravitational wave signals.In this thesis I discuss kilonovae (kNe) from BNS mergers with a focus on detection of kNe in the LSST survey. I will discuss the physics and modelling of kNe, including my work incorporating a viewing-angle dependence in the optical light curve modelling of BNS kNe. After setting the context for the Rubin Observatory and the LSST, I will describe work on optimising the observing strategy of the LSST to detect kNe from BNS mergers and the observing strategy features that impact detection. This work also indicates that a portion of the BNS mergers associated with kN detections in the LSST will be below the threshold for detection of their gravitational wave emission. Furthermore, I will discuss modelling a population of kNe from BNS mergers that is consistent with each merger’s associated gravitational-wave signal. This modelling includes a dependence of the kN on nuclear physics calibrated with detailed emulation of radiation-transport simulations. I conclude by summarising the scientific impact of this research and discussing future directions, such as: studying the BNS multi-messenger observational selection function for the LSST and concurrent gravitational wave detectors, detection of subthreshold signals, and the problem of classifying kN light curves.
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39.
  • Setzer, Christian, 1990- (författare)
  • Survey Astronomy with the LSST and Multimessenger Synergies
  • 2020
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Survey astronomy has become a powerful tool for discoveries in astrophysics and cosmology. In the coming years this approach will be taken even further with the start of the ten year survey of the Large Synoptic Survey Telescope. This instrument, with its unique capabilities in temporal sampling, single-image depth, and covered sky-area, will explore wholly new parts of parameter space of known systems and the Universe. The time at which this instrument is coming online also presents a unique opportunity, given the recent discovery of multimessenger transients emitting both gravitational and electromagnetic signals, to study the population of binary neutron star mergers in the Universe. This will be scientifically beneficial, not only for studies of the astrophysics of these sources, but also for determination of fundamental cosmological parameters. Given the reach of the LSST, it is expected that this instrument will detect these binary neutron star mergers to greater distances than detectable by current and near-term gravitational wave detectors. This presents further scientific opportunity to study the selection effects for detection of these sources in gravitational waves, and also potentially to recover the undetected gravitational wave signals counterpart to the detection their associated electromagnetic emission. In this thesis I give a brief summary of survey astronomy, the LSST instrument and observing strategy, multimessenger astronomy and the use of binary neutron star mergers as cosmological standard sirens. I then outline the work I have undertaken to optimise the observing strategy of the LSST to detect binary neutron star mergers, and the determination that indeed a significant portion of these detected objects will be subthreshold to detection of their gravitational wave emission. Then I outline the current work to produce self-consistent simulations of a population of these events which will be useful for studying the combined selection function of the LSST and concurrent gravitational wave detectors. This is all preparatory work to complete the full analysis of a program to recover the gravitational waves of BNS mergers detected by the LSST but below the detection threshold of a gravitational wave detector network. I outline some of what will go into this calculation and what work we plan to do. Additionally, I discuss the importance of addressing the classification problem for completing this scientific program.
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40.
  • 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.
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41.
  • Stopyra, Stephen, et al. (författare)
  • Quantifying the rarity of the local super-volume
  • 2021
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 507:4, s. 5425-5431
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the extent to which the number of clusters of mass exceeding 1015 M h−1 within the local super-volume(< 135 Mpc h−1) is compatible with the standard CDM cosmological model. Depending on the mass estimator used, we findthat the observed number N of such massive structures can vary between 0 and 5. Adopting N = 5 yields CDM likelihoods aslow as 2.4 × 10−3 (with σ 8 = 0.81) or 3.8 × 10−5 (with σ 8 = 0.74). However, at the other extreme (N = 0), the likelihood is oforder unity. Thus, while potentially very powerful, this method is currently limited by systematic uncertainties in cluster massestimates. This motivates efforts to reduce these systematics with additional observations and improved modelling.
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42.
  • 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.
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43.
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44.
  • 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.
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45.
  • 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.
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46.
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47.
  • Tsaprazi, Eleni, 1996- (författare)
  • Physics-informed inferences of galaxy clustering with Bayesian forward modelling
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, we showcase four novel approaches to constraining the relationship between cosmological observables and the large-scale structure. The majority of the energy content of the Universe in the concordance cosmological model remains largely unknown. Galaxy clustering can constrain the physical mechanism that links galaxy observations to structure formation. Traditional approaches to constraining this relation either rely on summary statistics of galaxy clustering, which lead to information loss or on ad-hoc assumptions, which can bias cosmological conclusions if accounted for improperly. The frameworks presented here ensure the self-consistent propagation of modelled observational uncertainties and extraction of high-order statistics from galaxy clustering. In Paper I, we investigate the potential of supernovae as large-scale structure probes, complementary to galaxy clustering for multi-tracer cosmology. If supernovae are biased relative to galaxies, their combination can improve the mapping of the large-scale structure. We find that supernovae cluster similarly to galaxies at 3.9 Mpc through cross-correlation of supernova locations with the gravitational tidal shear. In the second study, we generate supernova simulations informed about galaxy clustering, galaxy formation and evolution. We model supernova rates from the simulated star-formation histories and estimate the supernova bias with respect to the galaxy density field. We find that supernovae are less clustered than galaxies. The relative biasing signal was obscured in Paper I due to shot noise. In Paper II, we constrain galaxy intrinsic alignment -- a systematic effect in weak gravitational lensing and a probe of galaxy formation and evolution -- accounting for all high-order statistics and nonlinear structure growth down to 15.6 Mpc/h. We report a 4σ detection of galaxy intrinsic alignment, constant with luminosity, color and redshift at 20 Mpc/h. In Paper III, we present a framework to jointly constrain the large-scale structure and photometric galaxy clustering. Our approach is the first to infer the entire structure formation history and the filamentary pattern of the dark matter distribution, despite the large redshift uncertainties. Our approach guarantees the improvement of arbitrarily large photometric redshift uncertainties through galaxy clustering. 
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48.
  • Tsaprazi, Eleni, et al. (författare)
  • The large-scale environment of thermonuclear and core-collapse supernovae
  • 2022
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 510:1, s. 366-372
  • Tidskriftsartikel (refereegranskat)abstract
    • The new generation of wide-field time-domain surveys has made it feasible to study the clustering of supernova (SN) host galaxies in the large-scale structure (LSS) for the first time. We investigate the LSS environment of SN populations, using 106 dark matter density realisations with a resolution of ∼3.8 Mpc, constrained by the 2M+ + galaxy survey. We limit our analysis to redshift z < 0.036, using samples of 498 thermonuclear and 782 core-collapse SNe from the Zwicky Transient Facility’s Bright Transient Survey and Census of the Local Universe catalogues. We detect clustering of SNe with high significance; the observed clustering of the two SNe populations is consistent with each other. Further, the clustering of SN hosts is consistent with that of the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey DR12 spectroscopic galaxy sample in the same redshift range. Using a tidal shear classifier, we classify the LSS into voids, sheets, filaments, and knots. We find that both SNe and SDSS galaxies are predominantly found in sheets and filaments. SNe are significantly under-represented in voids and over-represented in knots compared to the volume fraction in these structures. This work opens the potential for using forthcoming wide-field deep SN surveys as a complementary LSS probe.
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49.
  • Widmark, Axel, 1989- (författare)
  • Dark Matter in the Solar System, Galaxy, and Beyond
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • There is evidence that dark matter constitutes a majority of the Universe's matter content. Yet, we are ignorant about its nature. Understanding dark matter requires new physics, possibly in the form of a new species of fundamental particles. So far, the evidence supporting the existence of dark matter is purely gravitational, ranging from mass measurements on galactic scales, to cosmological probes such as the cosmic microwave background radiation. For many proposed models of particle dark matter, the strongest constraints to its properties do not come from particle collider or direct detection experiments on Earth, but from the vast laboratory of space. This thesis focuses on such extra-terrestrial probes, and discusses three different indirect signatures of dark matter.(1) A first part of this thesis is about the process of dark matter capture by the Sun, whereby dark matter annihilating in the Sun's core could give rise to an observable flux of high-energy neutrinos. In this work, I was the first to thoroughly test the common assumption that captured dark matter particles thermalise to the Sun's core temperature in negligible time. I found that the thermalisation process is short with respect to current age of the Sun, for most cases of interest. (2) A second part concerns a radio signal associated with the epoch when the first stars were born. A measurement of this signal indicated an unexpectedly low hydrogen gas temperature, which was speculated to be explained by cooling via dark matter interactions. In my work, I proposed an alternative and qualitatively different cooling mechanism via spin-dependent dark matter interactions. While bounds coming from stellar cooling excluded significant cooling for the simple model I considered, perhaps the same cooling mechanism is allowed in an alternative dark matter model. (3) Thirdly, a significant part of this thesis is about the mass distribution of the Galactic disk, which can be measured by analysing the dynamics of stars under the assumption of equilibrium. Although most of the matter in the Galactic disk is made up of stars and hydrogen gas, exact measurements can still constrain the amount of dark matter. Potentially, dark matter could form a dark disk that is co-planar with the stellar disk, arising either from the Galactic accretion of in-falling satellites or by a strongly self-interacting dark matter subcomponent. Together with my collaborators, I made significant progress in terms of the statistical modelling of stellar dynamics. I measured the matter density of the solar neighbourhood using Galactic disk stars and data from the Gaia mission. I found a surplus matter density close to the Galactic mid-plane, with respect to the observed baryonic and extrapolated dark matter halo densities. This result could be due to a dark disk structure, a misunderstood density of baryons, or due to systematics related to the data or equilibrium assumption. I also developed an alternative method for weighing the Galactic disk using stellar streams. This method does not rely on the same equilibrium assumption for stars in the Galactic disk, and will be used to provide a complementary mass measurement in future work.The different indirect probes of dark matter discussed in this thesis span a great range of spatial scales − from stellar interactions relevant to our own solar system, to the matter distribution of the Milky Way, and even cosmological signals from the dawn of the first stars. Through the macroscopic phenomenology of dark matter, the microscopic particle nature of dark matter can be constrained. Doing so is a window into new physics and a deeper understanding of the Universe we live in.
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