This thesis aims at using novel machine learning techniques to test the dynamics of the Universe via the cosmological redshift-distance test. Currently, one of the most outstanding questions in cosmology is the physical cause of the accelerating cosmic expansion observed with supernovae. Simultaneously, tensions in measurements of the Hubble expansion parameter $H_0$ are emerging. Measuring the Universe expansion with next generation galaxy imaging surveys, such as provided by the Vera Rubin Observatory, offers the opportunity to discover new physics governing the Universe dynamics. In this thesis, with the long-term goal to unravel these peculiarities, we create a deep generative model in the form of a convolutional variational auto-encoder (VAE), trained with a "Variational Mixture of Posteriors" prior (VampPrior) and high-resolution galaxy images from the simulation project \texttt{TNG-50}. Our model is able to learn a prior on the visual features of galaxies and can generate synthetic galaxy images which preserve the coarse features (shape, size, inclination, and surface brightness profile), but not finer morphological features, such as spiral arms. The generative model for galaxy images is applicable to uses outside the scope of this thesis and is thus a contribution in itself. We next implement a cosmological pinhole camera model, taking angular diameter changes with redshift into account, to forward simulate the actual observation on a telescope detector. Building upon the hypothesis that certain features of galaxies should be of proper physical sizes, we use probabilistic triangulation to find the comoving distance $r(z,\Omega)$ to these in a flat ($K=0$) Universe. Using a sample of high-resolution galaxy images from redshifts $z\in[0.05,0.5]$ from \texttt{TNG-50}, we demonstrate that the implemented Bayesian inference approach successfully estimates $r(z)$ within $1\sigma$-error ($\Delta r_{\text{est}} = 140$ $(580)$ Mpc for $z=0.05$ $(0.5)$). Including the surface brightness attenuation and utilizing the avalanche of upcoming galaxy images could significantly lower the uncertainties. This thesis thus shows a promising path forward utilizing novel machine learning techniques and massive next-generation imaging data to improve and generalize the traditional cosmological angular-diameter test, which in turn has the potential to increase our understanding of the Universe. / Denna avhandling syftar till att använda nya maskininlärningstekniker för att testa universums dynamik via det kosmologiska rödförskjutningsavståndstestet. För närvarande är en av de mest framstående frågorna inom kosmologi den fysiska orsaken till den accelererande kosmiska expansionen som observerats med supernovor. Samtidigt uppstår spänningar i mätningar av Hubble-expansionsparametern $H_0$. Att mäta universums expansion med nästa generations galaxundersökningar, såsom de som ska genomföras av Vera Rubin Observatory, ger möjlighet att upptäcka ny fysik som styr universums dynamik. I den andan skapar vi i den här avhandlingen en djup generativ modell i form av en "convolutional variational auto-encoder" (VAE), tränad med en "Variational Mixture of Posteriors" prior (VampPrior) och högupplösta galaxbilder från simuleringsprojektet \texttt{TNG-50}. Vår modell kan lära sig en "prior" om galaxernas visuella egenskaper och kan generera syntetiska galaxbilder som bevarar de grova dragen (form, storlek, lutning och ytans ljusprofil), men inte finare morfologiska egenskaper, såsom spiralarmar. Den generativa modellen för galaxbilder är tillämplig på användningar som inte omfattas av denna avhandling och är därmed ett bidrag i sig. Därefter implementerar vi en kosmologisk hålkameramodell, med vilken hänsyn till förändringar i vinkelstorleken med rödförskjutning tas, för att framåt-simulera den faktiska observationen på en teleskopdetektor. Med utgångspunkt från hypotesen att galaxer i grunden borde ha gemensamma egenskaper med liknande fysiska storlekar, använder vi probabilistisk triangulering för att hitta avståndet (s.k. "comoving distance") $ r (z, \Omega) $ till dessa i ett platt ($ K = 0 $) universum. Med hjälp av ett urval av högupplösta galaxbilder från rödförskjutningar $ z \in [0.05,0.5] $ från \texttt {TNG-50} visar vi att den implementerade "Bayesian inference"-metoden framgångsrikt uppskattar $ r (z) $ inom $ 1 \sigma $ felmarginaler ($ \Delta r _ {\text{est}} = 140 $ $ (580) $ Mpc för $ z = 0,05 $ $ (0,5) $). Att inkludera dämpning i ytljusstyrka med rödförskjutning och att använda den massiva mängd av kommande galaxbilder skulle kunna minska den erhållna osäkerheten betydligt. Denna avhandling visar således en lovande väg framåt med nya maskininlärningstekniker och kommande enorma mängder av galaxbilder för att förbättra och generalisera det traditionella kosmologiska vinkeldiametertestet, vilket i sin tur har potentialen att öka vår förståelse om universum.

This project aims to obtain and interpret the measurements of the mean longitudinal magnetic field of the chemically peculiar star V1148 Ori. To achieve this aim 12 spectropolarimetric observations obtained by the CFHT using the spectropolarimeter ESPaDOnS were used. The method used to extract the magnetic field signatures from the spectra is called least-squares deconvolution. This method yields line-averaged profiles with a high signal-to-noise ratio. These mean line profiles are necessary to compute the mean longitudinal field. Results of the mean longitudinal field measurements were plotted as a function of the rotational phase, and to this, a sinusoidal function describing a dipolar field was fitted. The dipolar field parameters were computed for two different stellar radii. Inconsistent values for the stellar radii were obtained from the literature, and therefore we calculated two values for each of the parameters. For the surface polar field strength, we found BR1 = 17.38±0.30 kG and BR2 = 12.81±0.22 kG. The calculations involving one of the stellar radii gave results more consistent with previous findings. However, the discrepancy in parameter values could not be accounted for by the small uncertainties. So no definite conclusions can be drawn about the dipolar field parameters. Our fit aligns well with our longitudinal field measurements, no clear indication of any significant deviation from our model assumption, which suggests that the mean longitudinal field is consistent with a large-scale dipolar-like structure.

Magnetic fields play a crucial roll in the stellar activity and evolutionof stars. Despite much research there is much that we do notunderstand. Among Ap stars, empirical evidence has suggested a minimumthreshold for the dipolar magnetic field strength of Bp ≈ 300G.This thesis studies the magnetic field of the Ap star EP UMa usingthe oblique rotator model, which is modeling the star’s magnetic fieldas a dipole. The magnetic field was calculated through the StokesV- and I-spectrum emitted by the star. In total 16 observations ofthe Stokes V and I spectrum were used, collected from the spectropolarimeterNARVAL. These spectra were then analysed using the leastsquares deconvolution method, creating average Stokes V and I profiles,through which the magnetic field were calculated. The result ofthis study indicates a magnetic field of EP UMa with polar strengthof 74G ≤ Bp ≤ 196G, which is well below the suggested minimumthreshold.

ROCKE-3D is a contemporary Global Circulation Model allowing research into the complex processes behind the climate of planets. Using ROCKE-3D one can construct a model coupling atmosphere, land, and ocean revealing how the climate of a planet evolves over time. When constructing a model using ROCKE-3D, 2 different types of oceans can be used, one shallow without horizontal heat transfer and one fully coupled dynamic ocean. Simulations created using the different ocean types give rise to different results. In this project, the fractional habitability of the model 'planets' will be calculated using various methods in order to evaluate the differences between ocean types in ROCKE-3D simulations. There is also a hope to better understand how parameters such as rotation period and insolation, are affected when using different ocean types. The results show a large difference in predicted habitability fraction using two approximations for the ocean heat transport indicating that the Qflux approximation produces unrealistic models and should be avoided. / ROCKE-3D är en modern Global Circulation Model som tillåter forskning in i de komplexa processer som bygger planeters klimat. Vid användning av ROCKE-3D kan modeller som kopplar atmosfärer, land och hav konstrueras, detta kan avslöja hur en planets klimat utvecklas över tid. När en model konstrueras med ROCKE-3D kan 2 olika typer av hav användas, ett utan horisontell värmeöverföring som kallas för ett "Qflux" hav och ett fullt kopplat dynamiskt hav. Simulationer skapade med de olika havstyperna ger skillnad i resultat. I det här projektet, beräknas modell-planeternas fractional habitability för att evaluera skillnaden mellan havstyp i ROCKE-3D simulationer. Det finns även ett hopp för en bättre förståelse av hur parametrar, rotationsperiod och solinstrålning, påverkar när det är att föredra användningen av en viss havstyp. Resultaten visar att skillnaden i ""fractional habitability" mellan simulationer skapta med de 2 havstyperna minskar när solinstrålningen ökar, vilket visar att användandet av ett "Qflux" hav i skapandet av simulationer vid låg solinstrålning borde avrådas.

The Radio Neutrino Observatory in Greenland is situated at Summit Station. Due to its isolatedlocation the main power to support the autonomous radio stations is solar energy. However,during the winter months when there is no sun another strategy needs to be found. This projecthas been done within a group at Uppsala University, which aims to use wind turbines to powerthese stations during the long winter. We firstly analysed the performance and power output of SAVANT G turbine, a variation ofa Savonius turbine, for different periods of time and turbine system configurations. From thisanalysis we obtained the relation between the power and wind speed. Subsequently, this powercurve has been used in a model to predict the live time fraction of the radio stations during thewinter months. The model uses a database of one minute meteorological measurements fromNOAA at Summit from 2008 until 2022 and the power curve to calculate one minute powergeneration estimations. Knowing the electronic characteristics of the station, the model predictsthe charge status of the batteries and ultimately the number of hours that the batteries are chargedenough to power the radio station. The predicted live time fraction obtained with a parallel turbineconfiguration is 58%±7%, while for the parallel configuration with dual MPPT is 54%±4%. Theuncertainty was calculated taking the standard deviation of the fitted curve as upper and lowerpower curve limits using a 1% relative error and a 0.5W absolute error for each data point. Thenthese power curve limits were used to compute the live time fraction limits.1

The detection of high-energy neutrinos in the EeV range requires new detection techniques to cope with the small expected flux. The radio detection method, utilizing Askaryan emission, can be used to detect these neutrinos in polar ice. The propagation of the radio pulses has to be modeled carefully to reconstruct the energy, direction, and flavor of the neutrino from the detected radio signals. This thesis outlines the effect of birefringence in ice, which splits up the radio pulse into two orthogonal polarization components with slightly different propagation speeds. The signatures resulting from birefringence can help to reconstruct the energy and direction of the neutrino. In this thesis, the effect of birefringence is derived from first principles where the only free parameter of the model is the dielectric tensor as a function of depth and direction. The introduced model can propagate full RF waveforms which for the first time allows for the accounting of interference due to changing polarization eigenvectors during propagation. The model is available open-source through the NuRadioMC framework. The predictions of the model are compared to in-situ calibration data from the ARA and ARIANNA experiments and the implications for neutrino detection are discussed. / Detektionen av högenergetiska neutriner inom EeV-intervallet kräver nya detektionsmetoder för att handskas med flödet av neutriner, som förväntas vara mycket lågt. Radiodetektormetoden, som nyttjar Askaryanemission, kan användas för att detektera dessa neutriner i polarisarna. Radiopulsernas propagering måste modelleras noggrant för att rekonstruera energin, riktningen och smaken av neutrinon från detektorns radiosignaler. Denna avhandling beskriver effekten av dubbelbrytning i is, vilket delar upp radiopulsen i två ortogonala polarisationskomponenter med något annorlunda propageringshastigheter. De signaturer som uppstår av dubbelbrytning kan hjälpa till att rekonstruera energin och riktningen hos neutrinon. I denna avhandling härleds effekterna av dubbelbrytning från grunden, där den enda fria parametern i modellen är den dielektriska tensorn som funktion av djup och riktning. Modellen som introduceras kan propagera fullständiga RF-vågformer, vilket för första gången möjliggör hänsynstagandet av interferensen som orsakas av förändrade polarisationsegenvektorer som uppstår under propageringen. Modellen är tillgänglig som öppen källkod via NuRadioMC-ramverket. Modellens förutsägelser jämförs med in-situ kalibreringsdata från experimenten ARA och ARIANNA, och vilka implikationer som modellen har för neutrinodetektion diskuteras.

Three-dimensional (3D) planetary general circulation models (GCMs) have been derived from global climate models used to project 21st century changes in Earth's climate. GCMs are used to address questions regarding the climate-and habitability aspects of terrestrial planets within the solar system and assess the habitability of planets outside of the solar system, so called exoplanets. The development of GCMs has given rise to various results for concepts essential for determining potential habitable exoplanets such as the Habitable zone, hence intercomparison studies are of interest. In this project, the climate of an exoplanet with a static thermodynamic ocean will be modelled using ROCKE-3D, an open-source (3D) GCM developed at the NASA Goddard Institute for Space Studies. This is done in order to simulate the climate and examine how the simulations compare to other GCMs. The climate simulation will also be applied to an Earth-like planet in order to determine how an Earth-like climate will impact the results. We find that the climate on a rapidly rotating Aquaplanet receiving a G-star spectral energy distribution is surprisingly Earth-like. By contributing to a higher albedo, the ocean ice fraction of a rapidly rotating Aquaplanet was shown to impact the temperature and humidity structure considerably, despite the absence of Ocean Heat Transport. However, small differences between the simulations with and without sea ice were found for a tidally locked Aquaplanet receiving a M-star spectral energy distribution, which indicates that ROCKE-3D is not shutting off sea ice properly. Generally, ROCKE-3D shows similar results as CAM4 for the G-star runs and for the M-star, ROCKE-3D shows similar results to LMDG. / Tredimensionella (3D) planetariska allmänna cirkulationsmodeller (GCM) har härletts från de globala klimatmodeller som används för att projicera 2000-talets förändringar i jordens klimat. GCM används för att bemöta frågor om klimat- och beboelighetsaspekter av jordlika planeter inom solsystemet och bedöma beboeligheten för planeter utanför solsystemet, så kallade exoplaneter. Utvecklingen av GCM har gett upphov till olika resultat för begrepp som är väsentliga för att bestämma potentiella beboeliga exoplaneter såsom den beboerliga zonen, därför är jämförande studier av intresse. I detta projekt kommer klimatet för en exoplanet med ett statiskt termodynamiskt hav att modelleras av ROCKE-3D, en öppen källkod (3D) GCM utvecklad vid NASA Goddard Institute for Space Studies. Detta görs för att simulera klimatet och undersöka hur simuleringarna står sig i jämförelse med andra GCMs. Klimatsimuleringen kommer också att tillämpas på en jordliknande planet för att avgöra hur ett jordliknande klimat kommer att påverka resultaten. Vi finner att klimatet på en snabbt roterande vattenplanet som mottar en G-stjärnig spektral energifördelning är överraskande jordliknande. Genom att bidra till ett högre albedo visade havsisfraktionen av en snabbt roterande Aquaplanet att påverka temperatur- och fuktstrukturen avsevärt, trots frånvaron av havsvärmetransport. Små skillnader mellan simuleringarna med-och utan havsis påvisades för en tidvattenlåst vattenplanet som mottar en M-stjärnig spektral energifördelning, vilket tyder på att ROCKE-3D inte bortser havsis ordentligt. Generellt visar ROCKE-3D liknande resultat som CAM4 för en G-stjärna. För en M-stjärna visar ROCKE-3D liknande resultat som LMDG.

At higher redshift galaxies exhibit increasingly irregular and clumpy morphologies, withstar-forming clumps dominating the FUV output of their host galaxies thus being inti-mately related to star formation and the formation and evolution of galaxies. This workexamines star-forming clumps in a remarkable, young spiral galaxy at Cosmic Noon witha redshift ofz= 2.584, lensed by the galaxy cluster Abell 2744. To this aim, NIRCamobservations in 7 filter bands are utilized to determine photometry of clumps and performbroadband SED fitting to determine characteristic sizes, ages and masses and infer theirdynamical ages and mass surface densities. The clump within this galaxy spans a widerange of properties with sizes between 20 to 200 pc and masses between 105M⊙and109M⊙. While clumps are not resolved down to scales of individual star clusters, small,dense clumps may host star clusters. A number of clumps exhibits agestage>100 Myr,thus being able to survive feedback up to these timescales. This population of clumpsalso appears to be dynamically evolved and gravitationally bound as well as the denseststructures within the investigated sample, with roughly∼20% of clumps exhibiting masssurface densities comparable to bound stellar clusters in the local Universe.

No description available.

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 ).