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Viser treff 1-100 av 1277
(Master thesis / Masteroppgave, 2017)
We perform an investigation of quadru- and octopolar asymmetry in the CMB data by expanding the on the study of alignment and angular clustering of the dipole components of the CMB power distribution across multipoles l = ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Consistency relations of large-scale structures provide exact nonperturbative results for cross-correlations of cosmic fields in the squeezed limit. They only depend on the equivalence principle and the assumption of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(Master thesis / Masteroppgave, 2019)
(Master thesis / Masteroppgave, 2019)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
vom Marttens, R. F., et al. "Does a generalized Chaplygin gas correctly describe the cosmological dark sector?." Physics of the Dark Universe 15 (2017): 114-124.
© 2017. This manuscript version is made available under the ...
(Doctoral thesis / Doktoravhandling, 2014)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
Context: Various solar features can be seen in emission or absorption on maps of the Sun in the millimetre and submillimetre wavelength range. The recently installed Atacama Large Millimetre/submillimetre Array (ALMA) is ...
(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 ...
(Series / Serietittel, 1950)
(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)
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)
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)
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)
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)
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)
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)
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)
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)
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 ...
(Doctoral thesis / Doktoravhandling, 2013)
(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, 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, 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 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
We study the mean absorption spectrum of the Damped Lyα (DLA) population at z ~ 2.6 by stacking normalized, rest-frame-shifted spectra of ~27,000 DLA systems from the DR12 of the Baryon Oscillation Spectroscopic Survey ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
The primordial deuterium abundance probes fundamental physics during the big bang nucleosynthesis and can be used to infer cosmological parameters. Observationally, the abundance can be measured using absorbing clouds along ...
(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)
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)
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, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(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 ...
(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, 2020)
The standard model of cosmology has been quite successful in describing how baryonic matter and dark matter cluster by means of gravity, forming the structures we can see today while looking at the sky, and it can reproduce ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
In spite of their conjectured importance for the Epoch of Reionization, the properties of low-mass galaxies are currently still very much under debate. In this article, we study the stellar and gaseous properties of faint, ...
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- ...
(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 ...
(Journal article / Tidsskriftartikkel / SubmittedVersion, 2017)
Recent constrains on the sum of neutrino masses inferred by analyzing cosmological data, show that detecting a non-zero neutrino mass is within reach of forthcoming cosmological surveys. Such a measurement will imply a ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Motivated by observational and theoretical work that suggest very small-scale (≲ 1 pc) structure in the circumgalactic medium of galaxies and in other environments, we study Lyman-α (Lyα) radiative transfer in an extremely ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
We assess the impact of trapped Lyman α cooling radiation on the formation of direct collapse black holes (DCBHs). We apply a one-zone chemical and thermal evolution model, accounting for the photodetachment of H− ions, ...
(Doctoral thesis / Doktoravhandling, 2023)
The cosmic microwave background is one of the most prominent sources of cosmological information. Modern cosmological theories rely upon both small- and large-scale observations of the CMB. As a necessity, these observations ...
(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 / AcceptedVersion; Peer reviewed, 2017)
This is a post-peer-review, pre-copyedit version of an article published in Solar Physics. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11207-017-1095-2
(Doctoral thesis / Doktoravhandling, 2022)
In the standard model of the universe, the presence of a cold and dark form of matter is essential for explaining a wide range of observables, from the very largest scales such as the microwave background radiation, to ...
(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 ...
(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, 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, 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, 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, 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, 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, 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, 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 / 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 / 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, 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 / 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 / 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 / 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 / Masteroppgave, 2009)
(Master thesis / Hovedoppgave, 2007)
(Master thesis / Masteroppgave, 2007)
(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)
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 / 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 / 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, 2008)
(Master thesis / Masteroppgave, 2008)
(Master thesis / Masteroppgave, 2010)
(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, ...
(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, 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, 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, 2007)
(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, 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 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
We present observations of escaping Lyman Continuum (LyC) radiation from 34 massive star-forming galaxies (SFGs) and 12 weak AGN with reliably measured spectroscopic redshifts at $z\simeq 2.3\mbox{--}4.1$. We analyzed ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
Small bipolar magnetic features are observed to appear in the interior of individual granules in the quiet Sun, signaling the emergence of tiny magnetic loops from the solar interior. We study the origin of those features ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations, including ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
There have been ubiquitous observations of wave-like motions in the solar atmosphere for decades. Recent improvements to space- and ground-based observatories have allowed the focus to shift to smaller magnetic structures ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
Reduced relativistic gas (RRG) is a useful approach to describe the warm dark matter (WDM) or the warmness of baryonic matter in the approximation when the interaction between the particles is irrelevant. The use of Maxwell ...
(Doctoral thesis / Doktoravhandling, 2014)
(Doctoral thesis / Doktoravhandling, 2013)
This thesis presents an observational study of the dynamics of fine structure in the (mostly lower) atmosphere of solar active regions. The considered phenomena – Ellerman bombs, flocculent flows and coronal rain – are ...