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Now showing items 1-100 of 100
(Master thesis / Masteroppgave, 2016)
The universe is full of stuff we cannot see, neither directly or indirectly. We do not understand the nature of the mysterious dark matter and how it interacts with normal matter. Big Bang Nucleosynthesis (BBN) provides ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
The production of science-ready data from major solar telescopes requires expertise beyond that of the typical observer. This is a consequence of the increasing complexity of instruments and observing sequences, which ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
Late stages of stellar evolution are characterized by copious mass-loss events whose signature is the formation of circumstellar envelopes (CSE). Planck multi-frequency measurements have provided relevant information on a ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
The Planck survey provides unprecedented full-sky coverage of the submillimetre polarized emission from Galactic dust. In addition to the information on the direction of the Galactic magnetic field, this also brings new ...
(Master thesis / Masteroppgave, 2015)
In 2013 a new metric called TARDIS was introduced. This metric was published by Tippet and Tsang, and described a time machine. This thesis uses numerical methods to explore properties of this new metric. We start by ...
(Master thesis / Masteroppgave, 2015)
The ΛCDM model used in modern cosmology has major theoretical problems. To attempt to solve these many modified gravity theories have been proposed. We calculate velocity statistics (streaming pair-wise velocities and the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
We present unpublished observations of Comet Donati 1858 V recently recovered in an old storage facility at the University Observatory in Oslo. Carefully-made drawings reveal temporal changes in the appearance of this ...
(Master thesis / Masteroppgave, 2015)
In this thesis, we investigate statistical properties of the redshift zero matter distribution in disformal gravity through N-body simulations. The disformal model studied here is a conformally coupled field in a symmetron ...
(Master thesis / Masteroppgave, 2015)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We use these data to characterize the frequency dependence of dust emission. We make use of the Planck ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
Polarized emission observed by Planck HFI at 353 GHz towards a sample of nearby fields is presented, focusing on the statistics of polarization fractions p and angles ψ. The polarization fractions and column densities in ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust polarization fraction and ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
Analytical models are presented for currents along vertical magnetic field lines due to slow bulk electron motion in plasmas subject to a gravitational force. It is demonstrated that a general feature of this problem is a ...
(Doctoral thesis / Doktoravhandling, 2014)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We describe the data processing pipeline of the Planck Low Frequency Instrument (LFI) data processing centre (DPC) to create and characterize full-sky maps based on the first 15.5 months of operations at 30, 44, and 70 GHz. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The two fundamental assumptions of the standard cosmological model – that the initial fluctuations are statistically isotropic and Gaussian – are rigorously tested using maps of the cosmic microwave background (CMB) ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Based on cosmic microwave background (CMB) maps from the 2013 Planck Mission data release, this paper presents the detection of the integrated Sachs-Wolfe (ISW) effect, that is, the correlation between the CMB and large-scale ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Rotational transition lines of CO play a major role in molecular radio astronomy as a mass tracer and in particular in the study of star formation and Galactic structure. Although a wealth of data exists for the Galactic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We have constructed the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 100 to 857 GHz frequency channel maps from the Planck survey. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The dust-Hi correlation is used to characterize the emission properties of dust in the diffuse interstellar medium (ISM) from far infrared wavelengths to microwave frequencies. The field of this investigation encompasses ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Anomalous microwave emission (AME) is believed to be due to electric dipole radiation from small spinning dust grains. The aim of this paper is a statistical study of the basic properties of AME regions and the environment ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We use Planck HFI data combined with ancillary radio data to study the emissivity index of the interstellar dust emission in the frequency range 100–353 GHz, or 3–0.8 mm, in the Galactic plane. We analyse the region l = ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Using Planck data combined with the Meta Catalogue of X-ray detected Clusters of galaxies (MCXC), we address the study of peculiar motions by searching for evidence of the kinetic Sunyaev-Zeldovich effect (kSZ). By ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We explore the 2013 Planck likelihood function with a high-precision multi-dimensional minimizer (Minuit). This allows a refinement of the ΛCDM best-fit solution with respect to previously-released results, and the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
This paper presents an all-sky model of dust emission from the Planck 353, 545, and 857 GHz, and IRAS 100 μm data. Using a modified blackbody fit to the data we present all-sky maps of the dust optical depth, temperature, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The new cosmic microwave background (CMB) temperature maps from Planck provide the highest-quality full-sky view of the surface of last scattering available to date. This allows us to detect possible departures from the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We describe the processing of the 531 billion raw data samples from the High Frequency Instrument (HFI), which we performed to produce six temperature maps from the first 473 days of Planck-HFI survey data. These maps ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The Planck satellite provides a set of all-sky maps at nine frequencies from 30 GHz to 857 GHz. Planets, minor bodies, and diffuse interplanetary dust emission (IPD) are all observed. The IPD can be separated from Galactic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The Planck High Frequency Instrument (HFI) spectral response was determined through a series of ground based tests conducted with the HFI focal plane in a cryogenic environment prior to launch. The main goal of the spectral ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We analyse the implications of the Planck data for cosmic inflation. The Planck nominal mission temperature anisotropy measurements, combined with the WMAP large-angle polarization, constrain the scalar spectral index to ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
This paper characterizes the effective beams, the effective beam window functions and the associated errors for the Planck High Frequency Instrument (HFI) detectors. The effective beam is theangular response including the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We discuss the methods employed to photometrically calibrate the data acquired by the Low Frequency Instrument on Planck. Our calibration is based on a combination of the orbital dipole plus the solar dipole, caused ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We describe the detection, interpretation, and removal of the signal resulting from interactions of high energy particles with the Planck High Frequency Instrument (HFI). There are two types of interactions: heating of the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We present the current estimate of instrumental and systematic effect uncertainties for the Planck-Low Frequency Instrument relevant to the first release of the Planck cosmological results. We give an overview of the main ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
This paper presents the characterization of the in-flight beams, the beam window functions, and the associated uncertainties for the Planck Low Frequency Instrument (LFI). Knowledge of the beam profiles is necessary for ...
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2014)
The Euclid mission objective is to understand why the expansion of the Universe is accelerating by mapping the geometry of the dark Universe by investigating the distance-redshift relationship and tracing the evolution of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The European Space Agency’s Planck satellite, dedicated to studying the early Universe and its subsequent evolution, was launched 14 May 2009 and has been scanning the microwave and submillimetre sky continuously since 12 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We describe the all-sky Planck catalogue of clusters and cluster candidates derived from Sunyaev-Zeldovich (SZ) effect detections using the first 15.5 months of Planck satellite observations. The catalogue contains 1227 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We present new measurements of cosmic infrared background (CIB) anisotropies using Planck. Combining HFI data with IRAS, the angular auto- and cross-frequency power spectrum is measured from 143 to 3000 GHz, and the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The Planck Catalogue of Compact Sources (PCCS) is the catalogue of sources detected in the first 15 months of Planck operations, the “nominal” mission. It consists of nine single-frequency catalogues of compact sources, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Our velocity relative to the rest frame of the cosmic microwave background (CMB) generates a dipole temperature anisotropy on the sky which has been well measured for more than 30 years, and has an accepted amplitude of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Planck has produced detailed all-sky observations over nine frequency bands between 30 and 857 GHz. These observations allow robust reconstruction of the primordial cosmic microwave background (CMB) temperature fluctuations ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The Planck nominal mission cosmic microwave background (CMB) maps yield unprecedented constraints on primordial non-Gaussianity (NG). Using three optimal bispectrum estimators, separable template-fitting (KSW), binned, and ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Planck data have been used to provide stringent new constraints on cosmic strings and other defects. We describe forecasts of the CMB power spectrum induced by cosmic strings, calculating these from network models and ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The multi-frequency capability of the Planck satellite provides information both on the integrated history of star formation (via the cosmic infrared background, or CIB) and on the distribution of dark matter (via the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
On the arcminute angular scales probed by Planck, the cosmic microwave background (CMB) anisotropies are gently perturbed by gravitational lensing. Here we present a detailed study of this effect, detecting lensing ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
The Planck design and scanning strategy provide many levels of redundancy that can be exploited to provide tests of internal consistency. One of the most important is the comparison of the 70 GHz (amplifier) and 100 GHz ...
Dynamic properties along the neutral line of a delta spot inferred from high-resolution observations
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Delta (δ) spots are complex magnetic configurations of sunspots characterized by umbrae of opposite polarity sharing a common penumbra. In order to investigate the fine structure of the region separating the two magnetic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
This paper presents the Planck 2013 likelihood, a complete statistical description of the two-point correlation function of the CMB temperature fluctuations that accounts for all known relevant uncertainties, both instrumental ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
A dominant constituent in the dynamic chromosphere is spicules. Spicules at the limb appear as relatively small and dynamic jets that are observed to stick out everywhere. Many papers emphasize the important role spicules ...
Combining Planck data with large scale structure information gives a strong neutrino mass constraint
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We present the strongest current cosmological upper limit on the neutrino mass of ∑mν<0.18 eV (95% confidence). It is obtained by adding observations of the large-scale matter power spectrum from the WiggleZ Dark Energy ...
(Doctoral thesis / Doktoravhandling, 2013)
(Master thesis / Masteroppgave, 2013)
The existence of dark energy in the universe is hypothesized to explain the accelerated expansion of today’s universe and the inflationary expansion of very early universe; accelerated expansion of today’s universe is ...
(Master thesis / Masteroppgave, 2013)
The gravitational redshift in clusters of galaxies can be measured to probe gravity as was first done by Wojtak et al. (2011). Using N -body simulations we are able to analyze the gravitational redshift profiles for the ...
(Master thesis / Masteroppgave, 2013)
(Master thesis / Masteroppgave, 2013)
We investigate cosmologies where the accelerated expansion of the universe is driven by a fluid with an anisotropic equation of state.
If dark energy equation of state is anisotropic, the expansion rate of the universe ...
(Doctoral thesis / Doktoravhandling, 2013)
(Master thesis / Masteroppgave, 2012)
The Q/U-Imaging ExperimenT (QUIET) is a ground-based coherent polarimeter experiment, primarily targeting the detection of low-l B-mode polarization in the CMB. Such modes are a signature of primordial tensor perturbations, ...
(Master thesis / Masteroppgave, 2012)
The inverse-C shape of the bisector from the chromospheric Ca triplet spectral lines is a little understood phenomena. This spectral signature can give valuble information about the chromosphere, which is the least understood ...
(Master thesis / Masteroppgave, 2012)
The solar corona has a temperature of order 1 MK, which is almost 200 times the temperature of the underlying surface. This fact has puzzled solar physicists for more than six decades. As of today, most solar physicists ...
(Master thesis / Masteroppgave, 2012)
Inflation is a much discussed topic within the field of cosmology; it represents a time in the history of the Universe where a very rapid, exponential expansion was taking place. This expansion is needed in order for the ...
(Master thesis / Masteroppgave, 2011)
The existence of dark matter is a well established fact both due to galaxy rotation curves and also due to the CMB temperature anisotropies and the matter power spectra. According to the $\Lambda$CDM model, the so called ...
(Master thesis / Masteroppgave, 2011)
Spicules are relatively small, narrow and elongated structures that stick out above the edge of the solar disk. They are very dynamic and appear as jets that shoot out into the outer solar atmosphere. Up until recently, ...
(Master thesis / Masteroppgave, 2011)
The standard model of cosmology has proven to be a great success. Through measurements of the Cosmic Microwave Background radiation, cosmologists have been able to constrain parameters such as the age and geometry of the ...
(Master thesis / Masteroppgave, 2011)
There have been many reports on anomalies in the CMB from different research groups. In this work statistical tests using the gradients of the CMB temperature, applied to the seven year WMAP data, have been investigated. ...
(Master thesis / Masteroppgave, 2011)
This thesis is a study of the dynamics and virialization of cosmic structures in the framework of flat cosmological models where the properties of
the dark energy component plays an important role in the global and local ...
(Master thesis / Masteroppgave, 2010)
In this thesis the correlation between star formation and dynamical state of a statistical well defined selection of galaxy clusters have
been studied. From simulations and theory it is expected strong
correlations between ...
(Master thesis / Masteroppgave, 2010)
The solar chromosphere is a region where the thermodynamics are out of equilibrium, and realistic values of temperature and electron densities here are difficult to obtain. Hydrogen, being the most abundant element in solar ...
(Master thesis / Masteroppgave, 2010)
(Master thesis / Masteroppgave, 2010)
The theory of inflation gives certain predictions for the amount of primordial gravitational waves compared to the amount of density perturbations. These predictions are, in principle, verifiable through observation of the ...
(Master thesis / Masteroppgave, 2010)
We investigate scalar-field theories with a field-dependent coupling to matter and show the existence of a chameleon mechanism. The thin-shell solutions for a spherical body are found, and used to investigate the consequences ...
(Master thesis / Masteroppgave, 2010)
Neutrino cosmology is a very interesting field of research,
where properties of some of the smallest constituents of the universe
are probed by the very largest structures of the universe; large scale
structures of the ...
(Master thesis / Masteroppgave, 2010)
The statistical analysis of the Cosmic Microwave Background radiation to make estimates of the Power Spectrum is a comutationally heavy operation, involving large covariance matrices.
In this thesis I explore the possibility ...
(Master thesis / Masteroppgave, 2009)
En mulig forklaring på at universet gikk inn i en fase av akselerert ekspansjon for 5-6 milliarder år siden, er at energitettheten i universet inneholder et bidrag fra et dynamisk skalarfelt. Problemet med denne forklaringen ...
(Master thesis / Masteroppgave, 2009)
I have investigated the total energy of Friedmann-Robertson-Walker universes.
This is an interesting issue, because if the energy of the universe turns out not to be conserved, it will be in conflict with our common ...
(Master thesis / Masteroppgave, 2009)
The cosmic microwave background (CMB) radiation at 2.7 K is the leftover radiation from the Big Bang.
By studying this radiation we can extract much information about the universe we live in.
CMB experiments over the last ...
(Master thesis / Masteroppgave, 2009)
(Master thesis / Masteroppgave, 2008)
In between the Cosmic Microwave Background (CMB) and the instrument there are other sources of radiation, called foregrounds. The foregrounds radiate in the same frequency bands as the background, and cause contamination ...
(Master thesis / Masteroppgave, 2008)
Observations of the Cosmic Microwave Background is impaired by other astrophysical sources that also radiate in the microwave spectrum. These other, non-CMB sources are known as foregrounds. In this thesis, three different ...
(Master thesis / Masteroppgave, 2008)
Systematic anomalies that seem to follow the first ionisation
potential (FIP) of the minor, heavy elements at the sun, have been
found when comparing the observed elemental abundances in the upper
solar atmosphere with the ...
(Master thesis / Masteroppgave, 2008)
In-situ observations together with spectroscopic measurements show that the elemental abundance in the solar atmosphere varies from the photosphere to solar wind.
An enrichment for low First Ionisation Potential elements ...
(Master thesis / Masteroppgave, 2008)
(Master thesis / Masteroppgave, 2008)
(Master thesis / Masteroppgave, 2008)
The solar chromosphere has previously been thought to be a homogenic layer of the solar atmosphere, but better observations have made it evident that the chromosphere is a highly dynamic area.
Spicules are structures ...
(Master thesis / Masteroppgave, 2008)
Observations of how matter is distributed on different length scales in the universe are an important test of cosmological models. For example, such observations can give an upper limit for the mass of neutrinos: As the ...
(Master thesis / Hovedoppgave, 2007)
On Non-Gaussianity in the Cosmic Microwave Background : phenomenology and analysis Restricted Access
(Master thesis / Hovedoppgave, 2007)
The goals of this thesis are to provide a general introduction to CMB fundamentals, give an overview of non-Gaussianity analysis, and to compare the sensitivities of a selection of tests (Minkowski functionals, skeleton ...
A systematic search for gravitationally lensed quasars Restricted Access
(Master thesis / Masteroppgave, 2007)
Gravitational lensing has played an important role in cosmology since the discovery of the first gravitational lensing system in 1979 (Walsh et al.), where the quasar QSO 0957+561 can be seen in two images. Such multiple ...
(Master thesis / Masteroppgave, 2007)
(Master thesis / Masteroppgave, 2007)
(Master thesis / Masteroppgave, 2007)
(Master thesis / Masteroppgave, 2006)
Two galaxy clusters, Abell 1351 and Abell 1995, are examined using weak gravitational lensing
techniques. Mass maps are created, and the clusters' density and shear profiles are compared to
theoretical predictions.
Gravitational ...
(Master thesis / Hovedoppgave, 2005)
During inflation, the potential of the inflaton scalar field $\phi$,
drives the exponential expansion of the Universe. The nature of the
inflaton potential is presently unknown, but one hopes to learn more
from observations ...
(Master thesis / Hovedoppgave, 2003)
Through the two-point correlation function the effects of limited sky
coverage and discretisation of data on satellite observations of the
cosmic microwave background (CMB) is examined. Analytical expressions
for the ...
(Master thesis / Hovedoppgave, 2003)
The thesis examines the relation between
the magnetic field as measured by MDI and
the continuum intensity at four different
wavelengths (1319, 1199, 1037 and 910Å) as
measured by SUMER. A method for copointing
the instruments ...
(Master thesis / Hovedoppgave, 2002)
It is believed that the Broad Emission Line Region of Quasars consists of discrete clouds. Due to the suspected small size of a cloud, the radiation from clouds may be strongly amplified by gravitational microlensing.
It ...
(Master thesis / Hovedoppgave, 2002)
Five years (1992-1997, ~2650 images) of optical observations of the
gravitational lens system QSO 0957+561 were analyzed using a new
photometry package developed by Jan Teuber and me. My supervisor was
Prof. Rolf Stabell, ...
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