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.

Supernovae are cosmic explosions of cataclysmic proportion that signify the death of a star. While being interesting phenomena in their own right, their brightness also make them excellent probes of the early universe. Depending on the type of the progenitor star and the origin of the explosion different subjects can be investigated. In this dissertation the work I have done on the detection, characterisation and rate measurements of supernovae in the Stockholm VIMOS Supernova Search is presented. We have discovered 16 supernovae that exploded billions of years ago (or, equivalently, at high redshift, z). The observed brightness and colour evolution have been used to classify the supernovae into either thermonuclear (type Ia) or core collapse (type II) supernovae. The accuracy of the classification code is high, only about 5% of the supernovae are mistyped, similar to other codes of the same kind. By comparing the observed frequency of supernovae to simulations the underlying supernova rate at these high redshifts have been measured. The main result reported in this thesis is that the core collapse supernova rate at high redshift matches the rates estimated from looking at the star formation history of the universe, and agree well with previous studies. The rate of Ia supernovae at high redshift have been investigated by several projects, our results show a somewhat higher rate of Ia supernovae than expected. Proper estimates of the systematic errors of rate measurements are found to be very important. Furthermore, by using novel techniques for reducing and stacking images, we have obtained a galaxy sample containing approximately 50,000 galaxies. Photometric redshifts have been obtained for most of the galaxies, the resulting accuracy below z=1 is on the order of 10%. The galaxy sample has also been used to find high redshift sources, so called Lyman Break Galaxies, at z=3-5. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 4: Manuscript.

Type Ia supernovae can, for a short period of time, reach the same brightness as an entire galaxy. They are responsible for the creation of a large fraction of all heavy elements and can be used, as standard candles, to prove that the expansion of the universe is accelerating. Yet, we do not fully understand them. A basic picture where Type Ia supernovae are caused by thermonuclear explosions of white dwarfs is generally accepted, but the details are still debated. These unknowns propagate into systematic uncertainties in the estimates of cosmological parameters. A Monte Carlo framework, SMOCK, designed to model this error propagation, is presented. Evolution with time/distance and the nature of reddening are studied as the dominant astrophysical uncertainties. Optical spectra of Type Ia supernovae contain a wealth of information regarding the nature of these events, and can be used both to understand supernovae and to limit the systematic uncertainties in cosmological parameter estimates. We have reduced spectra observed with the Nordic Optical Telescope and the New Technology Telescope in conjunction with the SDSS-II supernova survey, and compared spectral properties (pseudo-Equivalent Widths and line velocities) of this sample with local supernovae.We have further studied possible systematic difficulties in such comparisons between nearby and distant supernovae, caused by noise and host galaxy contamination.Taking such uncertainties into account, we find a tentative evolution in supernova properties with redshift, compatible with expected demographic changes. Correlations with light curve shape found by other studies are confirmed. A tentative correlation with light curve colour is also presented. The latter could indicate an intrinsic component of the observed reddening, i.e. independent of interstellar dust in the host galaxy. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted.

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.

Vi har under vår verksamhetsförlagda utbildning, utifrån egna erfarenheter och genom att läsa forskning fått en förståelse för att barns föreställningar om naturvetenskapliga fenomen inte stämmer överens med verkligheten. Det har också gett oss en uppfattning om att det saknas läromedel inom astronomi för barn i de yngre åldrarna. Grundat utifrån detta valde vi att utveckla ett läromedel inom astronomi. Läromedlet är tänkt att vara lättillgängligt och lättanvänt för lärare, samt att läromedlet ska uppfylla ett av de centrala kraven i Lgr 11 för årskurs 1 till 3 inom naturvetenskap: ”Jordens, solens och månens rörelser i förhållande till varandra. Månens olika faser”. För att kunna ta reda på vad ett bra läromedel är och på så sätt få tips till vårt eget så genomfördes en enkät på våra partnerskolor. Vi har även genomfört en sammanställning av faktaböcker, skönlitteratur, läromedel och internetsidor. Materialet analyserades sedan med hjälp av en kvalitativ metod som har legat till grund i utvecklingen av läromedlet. Av enkäten har vi fått resultatet att pedagogerna eftersöker läromedel som bland annat inne­håller praktiska övningar kopplat till Lgr 11 och kopieringsunderlag. Av inventeringen av lit­teratur har vi kommit fram till resultatet att det saknas ett läromedel inom Astronomi för grundskolans yngre åldrar samt att ett sådant läromedel som pedagogerna i enkäten eftersö­ker inte finns på marknaden.   Läromedlet består av en lärarhandledning och en arbetsbok till eleverna. Lärarhandled­ningen är uppdelad efter rubrikerna saga, diskussionsfrågor, fakta och instruktioner till akti­viteter med tillhörande kopieringsunderlag. Arbetsboken är uppdelad i rubrikerna fakta, in­struktioner till aktiviteter och ordlista med svåra ord. Läromedlet bygger på metoderna: story­line, saga och högläsning. För att eleverna ska kunna ta till sig kunskaper om rymden så an­vänds verktyg som experiment och diskussionsfrågor. Läromedlet riktar sig främst till lärare och elever i grundskolans tidigare år, årskurs 1 till 3, men är även tänkt att kunna anpassas till barn i förskoleklass. / During our practical teacher training we became aware of children’s alternative conceptions in astronomy.  We turned our faces towards science education literature and found evidence that children’s conceptions is not corresponding to scientific explanations. We also realized that there is a lack of Swedish teaching aids in astronomy for younger children (school year 1-3), therefore we have chosen to develop a teaching tool in astronomy. The teaching material is meant to be accessible and easy to use for teachers, as well as the teaching material shall meet one of the key requirements of Lgr 11 for grades 1-3 in science: "The earth, sun and moon movements relative to each other. Phases of the moon". (own translation) To find out what a good teaching aid is and get tips to our own, we made a survey at our part­ner schools. We also performed a compilation of nonfiction, fiction, educational materials and Internet sites. The material was then analyzed with the help of a qualitative method which then formed the basis of the development of the teaching aid. Our main results from the survey are that the educators are seeking teaching aids which includes practical exercises linked to Lgr 11and photocopiable documents. From the inventory of literature, we have come to the conclusion that there is no Swedish teaching aid in Astronomy for the younger children in primary school and that such teaching materials that the teachers in the questionnaire are asking fore can’t be found in today’s market.   The teaching material consists of a teacher's guide and a workbook for students. The teach­er's guide is divided by the headlines: story, discussion topics, facts and instructions for ac­tivities with photocopiable documents. Students’ workbook is divided into headings: facts, instructions for activities and a glossary. These teaching materials are based on the methods: storyline, story and reading aloud. For students to be able to make meaning of Space the teaching aid contains tool as experiments and discussion questions. The teaching material is primarily aimed at teachers and students in primary school, grades 1 to 3, but the teaching material is also intended to accommodate children in preschool.

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.

The first stars in the Universe are thought to have formed in high dark matter density minihalos about 200 million years after the Big Bang. If these stars were able to contract dark matter into their stellar core while forming, some of them might have turned into dark stars (DSs) powered by the heat from dark matter annihilation. The possibilities for detection of DSs with the upcoming James Webb Space Telescope (JWST), scheduled for launch in 2021, is investigated in this work. With DS models generated in Spolyar et al. (2009) and atmosphere spectra from Gustafsson et al. (2008), spectral analysis has been carried out in MATLAB to find the unique colors of DSs compared to galaxies generated in Zackrisson et al. (2017) at z ≈ 7 − 11. It was found that lower temperature DSs (Teff ≤ 7800K) are distinguishable from galaxies and that they would be bright enough to be detected with the JWST provided a magnification factor of µ ≈ 160−1000 with the use of gravitational lensing. More recent DS models reveal that the DS of temperature Teff = 7800K is detectable even without the use of gravitational lensing. However, the probability of finding one today is really small due to DSs’ presumably short lifetime. The results of this work are hoped to give a better understanding of the properties of DSs and to increase the probability of finding one in the large imaging survey carried out by the JWST. / De första stjärnorna i universum antas ha bildats i minihalos med hög densitet av mörk materia omkring 200 miljoner år efter Big Bang. Om dessa stjärnor kunde dra till sig mörk materia under sitt bildande kan vissa av dem ha utvecklats till mörka stjärnor (s.k. dark stars) med mörk materia som energikälla. I detta arbete undersöks möjligheterna att upptäcka dem med det kommande James Webb Space Teleskopet (JWST) som planeras för uppskjutning år 2021. Med dark starmodeller genererade i Spolyar et al. (2009) och atmosfärspektra från Gustafsson et al. (2008) har spektralanalys utförts i MATLAB för att hitta vilka dark stars som går att urskilja från galaxer genererade i Zackrisson et al. (2017) vid z ≈ 7−11. Det visade sig att dark stars med låg temperatur (Teff ≤ 7800K) är urskiljbara och att de flesta av dessa dark stars, vid en förstoringsfaktor av µ ≈ 160−1000 vid användning av gravitationell linsning, är tillräckligt ljusstarka för att kunna detekteras. Jämfört med senare dark star-modeller skulle även Teff = 7800K DSs kunna detekteras utan användning av gravitaionell linsning. Sannolikheten att hitta en dark star är fortfarande väldigt liten på grund av dess förmodade korta livstid. Resultaten av detta arbete hoppas kunna ge en bättre förståelse för egenskaperna hos mörka stjärnor samt öka sannolikheten för detektion med JWST.

This is a study in how astronomy has been taught and is being taught in Swedish schools from 1905 to this date with an emphasis on the latest 30 years.   It concerns the regulations and methodical recommendations/curricula for Swedish junior high school/Swedish Comprehensive school for the years 1905, 1933, 1955, 1958, 1962, 1969, 1980 and 1994. The matter of integrating astronomy with other subjects and different methodical approaches is also considered. The problem with textbooks written only for one subject when the teacher tries to integrate subjects is emphasised. Physics textbook analysis shows that astronomy teaching has over the years developed, from being based on observations, to become more and more theoretical. It also shows that the amount of practical exercises has been fairly constant in physics textbooks during the seventies end eighties but now in the nineties varies a lot from textbook to textbook. The amount of liberty the textbook gives the pupil in finding knowledge and answers himself in the practical parts of astronomy was at its lowest during the seventies. It is now starting to give more and more freedom to the student, but it is not by any means near the level of freedom the pupil had during the twenties. Finally it shows how some Swedish schools are teaching astronomy in a more practical way and how a teacher can take advantage of modern information technology. Also the benefit from visiting an observatory is exemplified.

Comets are the most active around their perigees. The increased outgassing can lead to a coma thick enough to effectively absorb the solar EUV radiation, which engenders a self-shielding comet nucleus and inner layers of the ionosphere. This effect of self-shielding can be calculated by the attenuation of the sunlight according to the Beer-Lambert law. Here we focus on the perihelion of comet 67P/Churyumov-Gerasimenko, the target comet of the ESA Rosetta mission. We calculate attenuated photoionization frequencies and implement these into an ionospheric model constructed in a recent project work (by the same author). The ionization frequencies and ion number densities are calculated as a function of cometocentric distance and compared with the latest published peer-reviewed article by Heritier et al. (2017). Overall, the agreement is fairly good. The most significant difference is the discrepancy of number densities of O2 ions, which is higher in our model by nearly an order of magnitude. This discrepancy is attributed to the fact that Heritier et al (2017) only considered charge transfer processes for the formation of O2+, while we identify photoionization of O2 as the main production mechanism.