Observations of gamma-rays have been made from celestial sources such as active galaxies, gamma-ray bursts and supernova remnants as well as the Galactic ridge. The study of gamma rays can provide information about production mechanisms and cosmic-ray acceleration. In the high-energy regime, one of the dominant mechanisms for gamma-ray production is the decay of neutral pions produced in interactions of ultra-relativistic cosmic-ray nuclei and interstellar matter. Presented here is a parametric model for calculations of inclusive cross sections and transverse momentum distributions for secondary particles - gamma rays, elecrons, positrons, electron neutrinos, electron antineutrinos, muon neutrinos and muon antineutrinos - produced in proton-proton interactions. This parametric model is derived on the proton-proton interaction model proposed by Kamae et al.; it includes the diffraction dissociation process, Feynman-scaling violation and the logarithmically rising inelastic proton-proton cross section. To improve fidelity to experimental data for lower energies, two baryon resonance excitation processes were added; one representing the Delta(1232) and the other multiple resonances with masses around 1600 MeV/c^2. The model predicts the power-law spectral index for all secondary particles to be about 0.05 lower in absolute value than that of the incident proton and their inclusive cross sections to be larger than those predicted by previous models based on the Feynman-scaling hypothesis. The applications of the presented model in astrophysics are plentiful. It has been implemented into the Galprop code to calculate the contribution due to pion decays in the Galactic plane. The model has also been used to estimate the cosmic-ray flux in the Large Magellanic Cloud based on HI, CO and gamma-ray observations. The transverse momentum distributions enable calculations when the proton distribution is anisotropic. It is shown that the gamma-ray spectrum and flux due to a pencil beam of protons varies drastically with viewing angle. A fanned proton jet with a Gaussian intensity profile impinging on surrounding material is given as a more realistic example. As the observer is moved off the jet axis, the peak of the spectrum is moved to lower energies. / QC 20100803

Supernovae are some of the most energetic phenomena in the Universe and they have throughout history fascinated people as they appeared as new stars in the sky. Supernova (SN) 1987A exploded in the nearby satellite galaxy, the Large Magellanic Cloud (LMC), at a distance of only 168,000 light years. The proximity of SN 1987A offers a unique opportunity to study the medium surrounding the supernova in great detail. Powered by the dynamical interaction of the ejecta with the inner circumstellar ring, SN 1987A is dramatically evolving at all wavelengths on time scales less than a year. This makes SN 1987A a great ``laboratory'' for studies of shock physics. Repeated observations of the ejecta-ring collision have been carried out using the UVES echelle spectrograph at VLT. This thesis covers seven epochs of high resolution spectra taken between October 1999 and November 2007. Three different emission line components are identified from the spectra. A narrow (~10 km/s) velocity component emerges from the unshocked ring. An intermediate (~250 km/s) component arises in the shocked ring, and a broad component extending to ~15,000 km/s comes from the reverse shock. Thanks to the high spectral resolution of UVES, it has been possible to separate the shocked from the unshocked ring emission. For the unshocked gas, ionization stages from neutral up to Ne V and Fe VII were found. The line fluxes of the low-ionization lines decline during the period of the observations. However, the fluxes of the [O III] and [Ne III] lines appear to increase and this is found to be consistent with the heating of the pre-shock gas by X-rays from the shock interactions. The line emission from the ejecta-ring collision increases rapidly as more gas is swept up by the shocks. This emission comes from ions with a range of ionization stages (e.g., Fe II-XIV). The low-ionization lines show an increase in their line widths which is consistent with that these lines originate from radiative shocks. The high-ionization line profiles (Fe X-XIV) initially show larger spectral widths, which indicates that at least a fraction of the emission comes from non-radiative shocks.

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.

This thesis presents a brief review of gravitation and cosmology, and then gives an overview of the theory of cosmological perturbations; subsequently some applications are discussed, such as large-scale structure formation. Cosmological perturbations are here presented both in the Newtonian paradigm and in two di¤erent relativistic approaches. The relativistic approaches are (i) the metric approach, where small variations of the metric tensor are considered, and (ii) the covariant approach, which focusses on small variations of the curvature. Dealing with these two approaches also involves addressing the gauge problem –how to map an idealized world model into a more accurate world model.

The new CRISP filter at the Swedish 1-m Solar Telescope provides opportunities for observing the solar atmosphere with unprecedented spatial resolution and cadence. In order to benefit from the high quality of observational data from this instrument, we have developed methods for calibrating and restoring polarized Stokes images, obtained at optical and near infrared wavelengths, taking into account field-of-view variations of the filter properties. In order to facilitate velocity measurements, a time series from a 3D hydrodynamical granulation simulation is used to compute quiet Sun spectral line profiles at different heliocentric angles. The synthetic line profiles, with their convective blueshifts, can be used as absolute references for line-of-sight velocities. Observations of the Ca II 8542 Å line are used to study magnetic fields in chromospheric fibrils. The line wings show the granulation pattern at mid-photospheric heights whereas the overlying chromosphere is seen in the core of the line. Using full Stokes data, we have attempted to observationally verify the alignment of chromospheric fibrils with the magnetic field. Our results suggest that in most cases fibrils are aligned along the magnetic field direction, but we also find examples where this is not the case. Detailed interpretation of Stokes data from spectral lines formed in the chromospheric data can be made using non-LTE inversion codes. For the first time, we use a realistic 3D MHD chromospheric simulation of the quiet Sun to assess how well NLTE inversions recover physical quantities from spectropolarimetric observations of Ca II 8542 Å. We demonstrate that inversions provide realistic estimates of depth-averaged quantities in the chromosphere, although high spectral resolution and high sensitivity are needed to measure quiet Sun chromospheric magnetic fields. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Manuscript. Paper 3: Submitted. Paper 4: Submitted.

Optical lucky imaging polarimetry of HL Tau and XZ Tau in the Taurus-Auriga molecular cloud was carried out with the instrument PolCor at the Nordic Optical Telescope (NOT). The results show that in both the V- and R-band HL Tau show centrosymmetric structures of the polarization angle in its northeastern outflow lobe (degree of polarization ~30%). A C-shaped structure is detected which is also present at near-IR wavelengths (Murakawa, 2008), and higher resolution optical images (Stapelfeldt, 1995). The position angle of the outflow is 47.5+-7.5 degrees, which coincides with previous measurements and the core polarization is observed to decrease with wavelength and a few scenarios are reviewed. Measuring the outflow witdh versus distance and wavelength shows that the longer wavelengths scatter deeper within the cavity wall of the outflow. In XZ Tau the binary is partially resolved, it is indicated by an elongated intensity distribution. The polarization of the parental cloud is detected in XZ Tau through the dichroic extinction of starlight. Lucky imaging at the NOT is a great way of increasing the resolution, shifting increases the sharpness by 0.1 asec and selection the sharpest frames can increase the seeing with 0.4 asec, perhaps more during better conditions.

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.

Möjligheten att bestämma sin position med ett par meters noggrannhet varhelst på jordklotetman befinner sig har med tillgången till GPS blivit möjligt för alla som investerar i en GPSmottagare,således även Försvarsmakten. GPS har dock begränsningar som gör att tillgångentill tjänsten kan blockeras med enkla medel av såväl systemets ägare som andra. I Försvarsmaktenfinns det anvisningar inför anskaffandet av satellitpositioneringssystem som gör gällandeatt detta endast skall utgöra ett komplement till andra redundanta metoder. För militäraändamål har GPS ofta integrerats tillsammans med tröghetsnavigering där de båda metodernakompletterar varandra. Utan tillgång till GPS kommer positionsfelet i ett sådant system efteren kortare tid växa sig stort. I följande studie görs en inventering av alternativa positioneringsmetodervilka utöver GPS kan integreras tillsammans med tröghetsnavigering. Studienvisar att det finns metoder vilka antas kunna integreras i ett positioneringssystem samtidigtsom noggrannheten bibehålls. / The ability to determine one’s position with a couple of meters accuracy anywhere on earthhas become possible for all who invest in a GPS receiver, even the Swedish Armed Forces.However GPS has limitations that make it possible to deny access to the service by simplemeans from the owner of the system as well as of others. There are regulations within theSwedish Armed Forces for the procurement of satellite positioning systems that states theseshall be considered as complement to other, redundant methods. For military purposes GPS isoften integrated with an inertial positioning system where the two methods complement eachother. Without access to GPS in such a system the error growth is unlimited also within alimited period of time. The following study makes a survey of complementary methods thatbesides GPS is possible to integrate together with inertial navigation. The work indicates thatthere are methods which are assumed to use in an integrated positioning system with retainedaccuracy. / Avdelning: ALB - Slutet Mag 3 C-upps. Hylla: Upps. ChP T 06-08

Syftet med denna kvalitativa undersökning var att ta reda på hur barn förklarar att det blir natt. En intervjustudie gjordes med 21 skolbarn i år tre. Barnens svar kategoriserades enligt två olika svarsmodeller, tidigare utarbetade av Baxter och Brewer. Analysen av resultaten visade att barnens svar kunde tolkas olika beroende på vilken modell som användes. Även undersökningsmetoden visade sig vara avgörande för de svar vi fick. Vår undersökning gjordes ur ett sociokulturellt perspektiv där språkets nyanser och användandet av artefakter som tankeredskap legat till grund för resultaten och vår tolkning. Det visade sig att flera barn hade en vetenskaplig bild av fenomenet men saknade begrepp för att synliggöra detta. Dessa barn kunde med hjälp av papper, pennor och sitt kroppsspråk förtydliga sina tankar.

<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>