Molecular spectroscopy at radio wavelengths is a tool well suited for studying the composition and outgassing kinematics of cometary comae. This is particularly true for distant comets, i.e. comets at heliocentric distances greater than a few AU, where the excitation of molecules is inefficient other than for rotational energy levels. At these distances, water sublimation is inefficient, and cometary activity is dominated by outgassing of carbon monoxide. An observing campaign is presented, where the millimeter-wave emission from CO in comet 29P/Schwassmann-Wachmann 1 has been studied in detail using the Swedish-ESO Submillimetre Telescope (SEST). Coma models have been used to analyse the spectra. The production of CO is found to have two separate sources, one releasing CO gas on the nuclear dayside, and one extended source, where CO is produced from coma material, proposed to be icy dust grains. Radio observations of many molecules in comet C/1995 O1 (Hale-Bopp) have been carried out in a long-term international effort using several radio telescopes. An overview of the results is presented, describing the evolution of the gas production as the comet passed through the inner Solar system. Spectra recorded using the SEST, primarily of CO, for heliocentric distances from 3 to 11 AU are analysed in detail, also using coma models. The concept of icy grains constituting the extended source discovered in comet 29P/Schwassmann-Wachmann 1 is examined by theoretical modelling of micrometre-sized ice/dust particles at 6 AU from the Sun. It is shown that that such grains can release their content of volatiles on timescales similar to that found for the extended source.

The dynamical evolution of the spin axis direction due to gravitational and thermal factors is examined. It is found that the spin axis variations generally are regular and relatively small for the bodies in the asteroid main belt. There are also reasons to believe that this is the case for minor objects beyond the main belt. However, it is found that these regular variations are larger when the orbital inclination of the objects is increased. This effect may explain certain features in the spin vector distribution of the main belt asteroids, not possible to explain by collisional factors. The spin vector evolution of the asteroids in the inner solar system, including the Earth- and Mars-crossing objects, is often subjected to strong forces related to frequencies in the orbital evolution. The variations in the spin vector direction are then very large and often subjected to chaos. The larger frequency related obliquity zones of the Mars-crossers are usually regular while the zones of the Earth-Mars-crossers often are of a chaotic nature. The spin vector evolution of asteroids with comet-like orbits is often chaotic regardless of initial obliquity. For the inner solar system asteroids, it is often possible for an initial prograde spin to turn into a retrograde one, or vice versa, due to the frequency related phenomena. Though some spin vector directions seem to be more probable than other ones over time, there are no indications for an evolution towards a more prograde or a more retrograde spin vector distribution. The effects on the spin vector evolution from the thermal Yarkovsky force are examined for objects with radii larger than 50 m. This force will affect the orbital evolution and thus indirectly affect the spin vector evolution. However, it is found that the studied effects are minor as compared to the gravitationally related ones. This is true both for the diurnal and the seasonal variants of the Yarkovsky force.

The barred spiral galaxy M83 (NGC5236) has been observed in the 12CO J=1–0 and J=2–1 millimetre lines with the Swedish-ESO Submillimetre Telescope (SEST). The sizes of the CO maps are 100×100, and they cover the entire optical disk. The CO emission is strongly peaked toward the nucleus. The molecular spiral arms are clearly resolved and can be traced for about 360º. The total molecular gas mass is comparable to the total Hi mass, but H2 dominates in the optical disk. Iso-velocity maps show the signature of an inclined, rotating disk, but also the effects of streaming motions along the spiral arms. The dynamical mass is determined and compared to the gas mass. The pattern speed is determined from the residual velocity pattern, and the locations of various resonances are discussed. The molecular gas velocity dispersion is determined, and a trend of decreasing dispersion with increasing galactocentric radius is found. A total gas (H2+Hi+He) mass surface density map is presented, and compared to the critical density for star formation of an isothermal gaseous disk. The star formation rate (SFR) in the disk is estimated using data from various star formation tracers. The different SFR estimates agree well when corrections for extinctions, based on the total gas mass map, are made. The radial SFR distribution shows features that can be associated with kinematic resonances. We also find an increased star formation efficiency in the spiral arms. Different Schmidt laws are fitted to the data. The star formation properties of the nuclear region, based on high angular resolution HST data, are also discussed.

The X-ray Multi-mirror Mission, XMM-Newton was launched by the European Space Agency, ESA, in 1999. XMM-Newton carries six cameras, including a silicon pn-junction Charge Coupled Device, or pn-CCD camera. This camera has six operating modes, spatially as well as time resolved. The main objective of this project is to refine the Burst mode energy correction in order to align the measured energy spectra observed in the Burst mode with the spectra taken in the Full Frame mode. An observation of the line-rich supernova remnant called Cassiopeia A is used to evaluate the line positions in each mode such that the energy correction function used for the alignment can be modified accordingly. The analysis further treats the application of the correction on a source with a continuous spectrum, the Crab nebula. Discussion shows how to reduce eventual residuals in the Crab spectrum by modifying the correction function while keeping the alignment of the Cas-A spectra. The final product is an update of the corresponding published calibration file.

The predicted primordial lithium abundance differs from observations of unevolved halo stars on the Spite plateau by a factor two to three. Surface depletion due to atomic diffusion has been suggested as a cause of this so-called cosmological lithium problem. Evolutionary abundance trends indicative of atomic diffusion have previously been identified in the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), with stellar parameters deduced spectroscopically in a self-consistent manner. Abundances of five elements (Li, Mg, Ca, Ti, and Fe) were found to be in agreement with stellar structure models including the effects of atomic diffusion and a free-parameter description of turbulent mixing at the lowest efficiency compatible with the flatness of the Spite plateau. It is our aim to evaluate the interplay of modelling assumptions and theoretical predictions under various priors, e.g. the independent age determination using the white dwarf cooling sequence, and the high efficiency of turbulent mixing recently found compatible with halo field stars. We perform self-consistent spectroscopic abundance analyses at an expanded effective temperature scale inspired by results of new photometric calibrations from the infrared flux method. The resulting abundances are compared to predictions in a grid of theoretical isochrones, chosen in light of the priors for age and efficiency of turbulent mixing. We find that the observed abundance trends are not artefacts of the effective temperature scale, as it cannot be arbitrarily modified to flatten all trends. The inferred abundance trends seem to be in agreement with predictions for an age compatible with the white dwarf cooling sequence, and a limited range of weak turbulent mixing. The inferred initial lithium abundance of these stars is merely 30 % lower than the primordial abundance, discrepant at 1.5 standard deviations. Hence, a stellar solution to the cosmological lithium problem is still within reach.

<p>This thesis investigates the X-ray properties of the entire Stanghellini et al. (1998) complete sample of GHz Peaked Spectrum galaxies with redshift lower than 1. In total 19 sources are included mainly from observations made by the European space telescope, XMM-Newton. Out of these the analysis of seven "new" observations made between 2006 and 2008 are throughout described. Data from the new observations shows consistency with already analysed data. As a new result a tentative discovery of a bi-modal structure in the X-ray to radio luminosity ratio within the sample is presented.</p>

This thesis investigates the X-ray properties of the entire Stanghellini et al. (1998) complete sample of GHz Peaked Spectrum galaxies with redshift lower than 1. In total 19 sources are included mainly from observations made by the European space telescope, XMM-Newton. Out of these the analysis of seven "new" observations made between 2006 and 2008 are throughout described. Data from the new observations shows consistency with already analysed data. As a new result a tentative discovery of a bi-modal structure in the X-ray to radio luminosity ratio within the sample is presented.

Luminous Blue compact galaxies (BCGs) are metal-poor actively star-forming systems, characterised by bright ultraviolet and blue luminosities. Hubble Space Telescope high-resolution data have revealed that the luminous star-forming knots in these galaxies are composed of hundreds of young massive star clusters. In this work we present a systematic study of the star cluster populations in BCGs with important implications for the formation history of their host systems. The studied galaxies show recently increased star formation rates and a high fraction of massive clusters, probably as a result of minor/major merger events. The age distributions have a peak of cluster formation at only 3 - 4 Myr, unveiling a unique sample of clusters still partially embedded. A considerable fraction of clusters (30 - 50 %), mainly younger than 10 Myr, shows an observed flux excess between 0.8 and 2.2 μm. This so-called near-infrared (NIR) excess is impossible to reproduce even with the most recent spectral synthesis models (that include a self-consistent treatment of the photoionized gas). The origin of the NIR excess, which still remains unexplained, challenges our understanding of the cluster formation process under extreme conditions. The results achieved in this work have produced important insights into the cluster formation process in BCGs. We suggest that the BCG environment has most likely favoured the compression and collapse of giant molecular clouds into compact massive star clusters. The cluster formation efficiency (i.e., the fraction of star formation happening in star clusters) in BCGs is higher than the reported 8 - 10 %, for quiescent spirals and local star-forming galaxies. Luminous BCGs have a cluster formation efficiency comparable to luminous infrared galaxies and spiral starburst nuclei (the averaged value is  about 30 %), suggesting an important role of the merger event in the cluster formation. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted. Paper 5: Manuscript. Paper 6: Manuscript.

This thesis describes a timing calibration method for the detector array of the ALTO experiment. ALTO is a project currently at the prototype phase that aims to build a gamma-ray astronomical observatory at high-altitude in the Southern hemisphere. ALTO can be assumed as a hybrid system as each detector consists of a Water Cherenkov Detector (WCD) on top of a Scintillator Detector (SD), providing an increased signal to background discrimination compared to other WCD arrays. ALTO is planned to complement the Very-High-Energy (VHE) observations by the High Altitude Water Cherenkov (HAWC) gamma ray observatory that collects data from the Northern sky. By the time the full array of 1242 detectors is installed to the proposed site, ALTO together with HAWC and the future Cherenkov Telescope Array (CTA) will serve as a state-of-the-art detection system for VHE gamma-rays combining the WCD and the Imaging Atmospheric Cherenkov Telescope (IACT) techniques. When a VHE gamma-ray or cosmic-ray enters the Earth’s atmosphere, it initiates an Extensive Air Shower (EAS). These particles are sampled by the detector array and by checking the arrival times of nearby tanks, the method reveals whether a detector suffers from a time-offset. The data analyzed in this thesis derive from CORSIKA (COsmic Ray SImulation for KAscade) and GEANT4 (GEometry ANd Tracking) simulations of cosmic-ray events within the energy range of 1–1:6TeV, which mainly consist of protons. The high flux of this particular type of cosmic-rays, gives us a tool to statistically evaluate the results generated by the proposed timing calibration method. In the framework of this thesis, I have written code in Python programming language in order to develop the timing calibration method. The method identifies detectors that suffer from time-offsets and improves the reconstruction accuracy of the ALTO detector array. Different Python packages were used to execute different tasks: astropy to read filter-present-write large datasets, numpy (Numerical Python) to make datasets comprehensiveto functions, scipy (Scientific Python) to develop our models, sympy (Symbolic Python) to find geometrical correlations and matplotlib (Mathematical Plotting Library) to draw figures and diagrams. The current version of the method achieves sub-nanosecond accuracy. The next stepis to make the timing calibration more intelligent in order to correct itself. This self correction includes an agile adaptation to the data acquired for long periods of time, in order to make different compromises at different time intervals.

The detection of exoplanets has rapidly evolved to one of the most important frontiers of astronomical and astrophysical research. The recent decades have seen the development of various techniques for detecting exoplanets. Of these approaches the transit method has received particular interest and has lead to the largest number of discoveries to date. The Kepler K2 mission is an ongoing observational survey, which has generated light curves for thousands of stars, a large fraction of which have yet to be fully explored. To discover and characterize the transiting planets hosted by the respective stars, extensive transit screens are required. However, implementing a pipeline for transit analyses is not straight forward, considering the light curve properties of different survey, the rapid changes brought by technological advancements, and the apparent lack of a golden standard with respect to the applied methodology. The project has reviewed several aspects of exoplanet detection via the transit method. Particular focus was placed on the identification of a suitable workflow covering the relevant steps to move from raw light curve files to a final prediction and characterization of transiting planetary candidates. Adhering to the identified strategy, the major part of the project then dealt with the implementation of a pipeline that integrates and executes all the different steps in a streamlined fashion. Of note, primary focus was placed on the actual selection and implementation of methods into an operational pipeline, but due to the given time constraints extensive optimizations of each individual processing step was outside the scope of this project. Nevertheless, the pipeline was employed to predict transit candidates for K2 campaigns C7, C8, C10, C11, and C12. A comparsion of the most conservative predictions from campaigns C7 and C10 with previously reported exoplanet candidates demonstrated that the pipeline was highly capable of discovering reliable transit candidates. Since campaigns C11 and C12 have not yet been fully explored, the respective candidates predicted for those campaigns in the current project might thus harbour novel planetary transit candidates that would be suitable for follow-up confirmation runs. In summary, the current project has produced a pipeline for performing transiting exoplanet searches in K2 data, which integrates the steps from raw light curve processing to transit candidate selection and characterization. The pipeline has been demonstrated to predict credible transit candidates, but future work will have to focus on additional optimizations of individual method parameters and on the analysis of transit detection efficiencies.