Philosophiae Doctor - PhD / The next generation of radio telescopes will revolutionize cosmology by providing large three-dimensional surveys of the universe. This work presents forecasts using the technique 21cm intensity mapping (IM) combined with results from the cosmic microwave background, or mock data of galaxy surveys. First, we discuss prospects of constraining curvature independently of the dark energy (DE) model, finding that the radio instrument HIRAX will reach percent-level accuracy even when an arbitrary DE equation of state is assumed. This is followed by a study of the potential of the multi-tracer technique to surpass the cosmic variance limit, a crucial method to probe primordial non-Gaussianity and large scale general relativistic e↵ects. Using full sky simulations for the Square Kilometre Array phase 1 (SKA 1 MID) and the Large Synoptic Survey Telescope (LSST), including foregrounds, we demonstrate that the cosmic variance contaminated scenario can be beaten even in the noise free case. Finally, we derive the signal to noise ratio for the cosmic magnification signal from foreground HI intensity maps combined with background galaxy count maps. Instruments like SKA1 MID and HIRAX are highly complementary and well suited for this measurement. Thanks to the powerful design of the planned radio instruments, all results confirm their potential and promise an exciting future for cosmology.

>Magister Scientiae - MSc / Future radio surveys as the Square Kilometer Array (SKA) and its precursor, the "Meer" Karoo Array Telescope (MeerKAT), will map the Neutral Hydrogen (HI) in large areas of the sky using the intensity mapping (IM). HI IM is currently one of the most promising ways of accessing the Large-Scale Structure of the Universe. The distribution of matter in the Universe not only encodes its composition but also how it evolves and its initial conditions. An effect on the matter distribution that will be detected by the SKA on the post re-ionization Universe are the Baryonic Acoustic Oscillations (BAO). While it has been shown that in single dish mode the SKA can measure the BAO peak in the radial 21cm power spectrum at low redshifts, this possibility has not yet been studied in detail for the MeerKAT. In this thesis we construct a set of full sky simulations to test how well MeerKAT will be able to extract the BAO wiggles along the line of sight. These simulations are done for the frequencies corresponding to MeerKAT L-band. The maps combine the cosmological HI signal, systematic noise, cosmological foregrounds and the instrumental telescope beam. A model-independent estimator is used to extract the BAO wiggles by subtracting a smooth polynomial component from the 21cm radial power spectrum. We test with simulations if this estimator is biased and the signal to noise of the extraction. We conclude that we are able to remove contaminants and recover the cosmological HI signal while not risking the recovery of the BAO signal. We investigate the effects of varying the sky area and the observational hours on the signal to noise ratio for the BAO wiggles. We found that for a HI IM experiment using MeerKAT, the optimal sky area to detect the BAO along the line of sight is 50% of the sky. With a signal-to-noise ratio of 3.37. This can be achieved with 2000 hours of exposure time

Weak gravitational lensing has developed to be one of the most powerful tools for studying the (dark) matter distribution in the Universe. Most weak lensing studies thus far were con- ducted in the optical and near infrared. Measuring weak lensing in the radio though, provided it is feasible, can be very advantageous. One can exploit the well known and deterministic beam pattern of a radio telescope and the polarisation information in radio data to reduce shape biases and intrinsic alignment effects respectively. Combining the information from an optical and a radio survey can also help remove systematics from both datasets. This has motivated this study that uses archival radio and optical data to treat telescope systematics and measure an unbiased weak lensing signal using shape information derived from radio observations. Using simulations I have shown that an unbiased convergence cross power spectrum can be measured in the presence of the large scale (θ > 1◦) systematics detected in FIRST and SDSS. The method however amplifies the uncertainties by a factor ∼2.5 compared to the errors due to cosmic variance and noise due to galaxy intrinsic shape alone. Using the shape information from the two surveys I measure a Ckappakappa spectrum signal that is inconsistent with zero at the 2.7sigma. The placed constraints are consistent with the expected signal in the concordance cosmological model assuming recent estimates of the cosmological parameters from the Planck satellite and literature values for the median redshifts of SDSS and FIRST.Through simulations I also show that I can successfully remove position based small scale systematics (θ5). Using the deconvolved information for the resolved sources I calculate a FWHM median size and flux density of 0.5'' and 300μJy respectively. Comparing the source number density and RMS noise of the study with those of FIRST, I extrapolate to predict that the number density of sources at > 5sigma will be ∼5arcmin-2, assuming the target noise threshold for the survey is reached.

Apresentamos fotometria profunda (V ~ 25,5) nas bandas V e I obtidas com a Wide Field and Planetary Camera 2 a bordo do telesc opio espacial Hubble para 7 campos distantes ~5º do centro da Grande Nuvem de Magalhães. Ajustamos isócronas aos diagramas cor-magnitude a fim de identficar diferentes populaões estelares nestes campos. Uma população velha (τ > 10¹º anos) foi encontrada em todos os campos. Alguns eventos de elevada formação estelar, com idades entre 2 x 109 e 4 x 109 anos, foram também encontrados em alguns campos localizados na região N/NO. Funções de luminosidade de estrelas de baixa massa (m ≤ 1; 1msol) foram obtidas para todos os campos. Aparentemente não há diferenças na mistura de populações entre os campos como sugerido através do teste Kolmogorov-Smirnov aplicados as funções de luminosidade. Finalmente, derivamos perfis de densidade para estrelas velhas e de idade intermediária. O primeiro apresenta uma inclinação levemente maior quando comparado com o último.

With the Hubble Space Telescope and its near-infrared capabilities, it is now possible to probe deep into the epoch of reionization, improving our understanding of galaxy evolution through cosmic history. Whether it is via colour-selection or fitting the spectral energy distribution, it has now become routine to amass large samples of galaxies as distant as redshift z = 8, with the current frontier of observations at z = 9 - 10. The new Hubble Frontier Fields (HFF) programme provides the potential to study the most distant, intrinsically faint background galaxies through the gravitational lensing provided by a foreground galaxy cluster. This thesis presents a study of the galaxy population at z = 9 - 10 that exploits this phenomenon. In an initial search of the first two HFF cluster+parallel pointings, Abell 2744 and MACS J0416.1-240, we unveil twelve candidate high-redshift galaxies at 8:4 < z < 9:5, and are thus able to place constraints on the galaxy UV luminosity function at z = 9. For this study, we employ the "blank-field" method, whereby we confine attention to only the homogeneously deep, relatively low-magnification regions of the imaging. We are able to demonstrate evidence for a smooth decline in UV luminosity density between z ≃ 8 and z ≃ 9, in contrast to reports in the recent literature of a steep drop-off at these redshifts. We extend this study to include the new MACS J0717.5+3745 and MACS J1149+2223 cluster+parallel pointings, and supplement the search for z ≃ 9-10 galaxies with twenty CLASH cluster pointings. From a search over an area ≃ 130 sq. arcmin, we are able to present 33 galaxy candidates with photometric redshift solutions in the range 8:4 < zphot < 11:2. Our new results reinforce the argument for a smoothly-evolving LF between z ≃ 8 and z ≃ 9, which can be equally well modelled by a factor ≃ 2 drop in Φ* or a dimming of ≃ 0:5 mag in M*. We also find evidence that this smooth decline in the UV luminosity function, and hence UV luminosity density, continues to z ≃ 10. As well as considering the galaxy population at z = 9 - 10, this thesis presents a study of the stellar populations of galaxies at z ≥ 5. We are able to extend the luminosity baseline and measure the colour-magnitude relation at z = 5 - 8, through a combination of probing intrinsically faint galaxies behind cluster fields, in conjunction with both ultra-deep, pencil beam imaging such as the Hubble Ultra Deep Field (HUDF) and wider, shallower imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). This allows us to make inferences about the underlying stellar populations of galaxies at these epochs, and provides a unique insight into the colours of intrinsically faint, lensed galaxies as faint as M1500 ~ -14. We find that the data is consistent with an essentially unchanged average UV slope (β) for a given luminosity across the redshift range z = 5-8. We also find that the data favours a mild flattening of the colour-magnitude relation with redshift between z = 5 and z = 8.

Two-axis gimbals are frequently used to point cameras and telescopes at various points of interest for surveillance, science, and art. The rotation of a two-axis gimbal system is governed by nonlinear angular momentum equations of motion. This paper presents a method for slewing a telescope in space with a gimbaled sensor attached to a nominally non-rotating spacecraft using two seventh order polynomial input functions to characterize torques. To accomplish this task, picking the optimal coefficients of the seventh order polynomial was necessary. It was also desired to use constraint equations to limit the excursion, angular velocity, angular acceleration, and jerk of the gimbal. A Matlab code was developed for this purpose. Matlab’s fmincon was used to do the optimization, and a comparison to a previously validated one-degree-of-freedom (DOF) model was presented for validation of the nonlinear, two-degree-of-freedom model. Results for a fully constrained 2 DOF slew maneuver were also shown. This thesis demonstrates that seventh order polynomial torques can be used to accurately slew a telescope in space using nonlinear equations of motion.

This thesis presents the results of a combination of new observations with the Parkes telescope of neutral hydrogen (HI) in the Small Magellanic Cloud (SMC) with an Australia Telescope Compact Array aperture synthesis mosaic. The data are used to study the HI distribution and mass, the velocity field and rotation curve of the SMC, as well as to probe the 3-D structure of the SMC. A kinematic study of the HI data reveals the existence of three supergiant shells which were previously undetectable in the ATCA data alone. The HI spatial power spectrum has been investigated over a range of contiguous scale sizes wider than those previously achieved in any other galaxy. This thesis also demonstrates that the infrared data obtained with the Infrared Astronomical Satellite for the SMC can be successfully reconstructed with much higher resolution using the Pyramid Maximum Entropy algorithm. The new infrared (IR) data are used to study the integrated IR spectrum, the dust temperature and dust column density in the SMC. The high resolution HI and IR data enable an investigation of the spatial correlation of dust and gas and the assumption of the dust and gas being well-mixed in the ISM. The spatial power spectrum of the dust column density shows that, as with the HI power spectrum, there is no preferred scale size for dust clouds. The remarkable similarity of the spatial power spectra for the HI and dust column density distributions suggests a unique hierarchical structure organisation for the ISM in the SMC. Such an organisation is likely to be governed by the Kolmogorov type turbulence and could be described by fractal nature with the volume fractal dimension of 2.4. / Doctor of Philosophy (PhD)

To date, more than 300 planets orbiting stars other than our sun have been discovered using a range of observing techniques, with new discoveries occuring monthly. The work in this thesis focused on the detection of exoplanets using the transit method. Planets orbiting close to their host stars have a roughly 10 per cent chance of eclipsing (transiting) the star, with Jupiter?sized planets causing a one per cent dip in the flux of the star over a few hours. A wealth of orbital and physical information on the system can be extracted from these systems, including the planet density which is essential in constraining models of planetary formation. To detect these types of planets requires monitoring tens of thousands of stars over a period of months. To accomplish this, we conduct a wide-field survey using the 0.5-meter Automated Patrol Telescope (APT) at Siding Spring Observatory (SSO) in NSW, Australia. Once candidates were selected from the data?set, selection criteria were applied to separate the likely planet candidates from the false?positives. For this thesis, the methods and instrumentation used in attaining data and selecting planet candidates are discussed, as well as the results and analysis of the planet candidates selected from star fields observed from 2004?2007. Of the 65 planet candidates initially selected from the 25 target fields observed, only two were consistent with a planet transit. These candidates were later determined to be eclipsing binary stars based on follow up observations using the 40-inch telescope, 2.3-m telescope, and the 3.9-m Anglo-Australian Telescope, all located at SSO. Additionally, two planet candidates from the SuperWASP-North consortium were observed on the 40-inch telescope. Both proved to be eclipsing binary stars. While no planets were found, our search methods and results are consistent with successful transit surveys targeting similar fields with stars in a similar magnitude range and using similar methods.

Le satellite Fermi a été lancé le 11 juin 2008, avec à son bord le Large Area Telescope (LAT). Le LAT est un télescope sensible au rayonnement gamma de 20 MeV à plus de 300 GeV. Au début de l'activité de Fermi, neuf pulsars jeunes et énergétiques étaient connus dans le domaine gamma. Le nombre de détections de pulsars par le LAT prédit avant lancement était de plusieurs dizaines au moins. Le LAT permettait également l'étude des pulsars milliseconde (MSPs), jamais détectés avec certitude à très haute énergie jusqu'alors. Cette thèse aborde dans un premier temps la campagne de chronométrie des pulsars émetteurs radio et/ou X, candidats à la détection par le LAT, en collaboration avec les grands radiotélescopes et télescopes X. Cette campagne a permis la recherche de signaux gamma pulsés avec une grande sensibilité. En outre, la plupart des MSPs galactiques ont été suivis dans le cadre de cette campagne, sans biais de sélection a priori sur cette population d'étoiles. Pour la première fois, des pulsations ont été détectées pour huit MSPs galactiques au-dessus de 100 MeV. Quelques bons candidats à une détection prochaine apparaissent. Une recherche similaire a été conduite pour des MSPs d'amas globulaires, sans succès à présent. L'analyse des courbes de lumière et des propriétés spectrales des huit MSPs détectés révèle que leur rayonnement gamma est relativement similaire à celui des pulsars ordinaires, et est vraisemblablement produit dans la magnétosphère externe. Cette découverte suggère que certaines sources non identifiées sont des MSPs, pour l'instant inconnus.

<p>The <em>IceCube telescope</em> is built within the ice at the geographical South Pole in the middle of the Antarctica continent. The purpose of the telescope is to detect muon neutrinos, the muon neutrino being an elementary particle with minuscule mass coming from space.</p><p>The detector consists of some 5000 DOMs registering photon hits (light). A muon neutrino traveling through the detector might give rise to a track of photons making up a straight line, and by analyzing the hit output of the DOMs, looking for tracks, neutrinos and their direction can be detected.</p><p>When processing the output, triggers are used. Triggers are calculation- efficient algorithms used to tell if the hits seem to make up a track - if that is the case, all hits are processed more carefully to find the direction and other properties of the track.</p><p>The Track Engine is an additional trigger, specialized to trigger on low- energy events (few track hits), which are particularly difficult to detect. Low-energy events are of special interest in the search for Dark Matter.</p><p>An algorithm for triggering on low-energy events has been suggested. Its main idea is to divide time in overlapping time windows, find all possible pairs of hits in each time window, calculate the spherical coordinates θ and ϕ of the position vectors of the hits of the pairs, histogram the angles, and look for peaks in the resulting 2d-histogram. Such peaks would indicate a straight line of hits, and, hence, a track.</p><p>It is not believed that a software implementation of the algorithm would be fast enough. The Master's Thesis project has had the aim of developing an FPGA implementation of the algorithm.</p><p>Such an FPGA implementation has been developed. Extensive tests on the design has yielded positive results showing that it is fully functional. The design can be synthesized to about 180 MHz, making it possible to handle an incoming hit rate of about 6 MHz, giving a margin of more than twice to the expected average hit rate of 2.6 MHz.</p>