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Now showing items 101-200 of 1297
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2016)
The Euclid mission objective is to understand why the expansion of the Universe is accelerating through by mapping the geometry of the dark Universe by investigating the distance-redshift relationship and tracing the ...
(Master thesis / Masteroppgave, 2015)
In this thesis we have implemented a basic radiative transfer code to model the radial Lyα scattering rate around the epoch when the first stars and galaxies start forming, and ionizing their surroundings. The model, builds ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
Galactic outflows are known to consist of several gas phases; however, the connection between these phases has been investigated little and only in a few objects. In this paper, we analyse Multi Unit Spectroscopic Explorer ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
We summarize panchromatic Extragalactic Background Light data to place upper limits on the integrated near-infrared surface brightness (SB) that may come from Population III stars and possible accretion disks around their ...
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)
The heating of the solar chromosphere and corona to the observed high temperatures, imply the presence of ongoing heating that balances the strong radiative and thermal conduction losses expected in the solar atmosphere. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2008)
Conditional sampling methods are generalized by applying a matched-filter on the reference signal. This generalized method is illustrated by data obtained in a magnetized toroidal plasma without rotational transform. By ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2012)
We consider issues related to the conformal mapping between the Einstein and Jordan frames in f(R) cosmology. We consider the impact of the conformal transformation on the gauge of a perturbed system and show that unless ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
© ESO, 2015
(Master thesis / Masteroppgave, 2021)
Although modern cosmology has been able to reveal a wealth of information about the Universe, there are still many questions to be answered, such as the details of how the first stars ionized the Universe in the Epoch of ...
(Doctoral thesis / Doktoravhandling, 2022)
The Sun's chromosphere, which is the atmospheric layer located between the solar surface (photosphere) and the solar corona, holds the key to comprehend why the corona is thousands of times hotter than the Sun's surface. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
The Fe i 6173 Å line is widely used in the measurements of vector magnetic fields by instruments including the Helioseismic and Magnetic Imager (HMI). We perform non-local thermodynamic equilibrium calculations of this ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Reproduced with permission from Astronomy & Astrophysics, © ESO, 2016
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
An interaction between dark matter and dark energy, proportional to the product of their energy densities, results in a scaling behavior of the ratio of these densities with respect to the scale factor of the Robertson-Walker ...
(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
We investigate the compatibility of the Symmetron with dark energy by introducing a non-minimal kinetic term associated with the Symmetron. In this new model, the effect of the friction term appearing in the equation of ...
(Master thesis / Masteroppgave, 2014)
Solving the non-LTE radiative transfer problem in stellar atmospheres is computationally demanding. There is therefore an interest to investigate new methods to solve this problem effectively. A numerical method, multigrid, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Planck observations at 353 GHz provide the first fully sampled maps of the polarized dust emission towards interstellar filaments and their backgrounds (i.e., the emission observed in the surroundings of the filaments). ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Ellerman bombs (EBs) are brightenings in the Hα line wings that are believed to be caused by magnetic reconnection in the lower atmosphere. To study the response and evolution of the chromospheric line profiles, we perform ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands observatories as part of the general optical follow-up programme undertaken ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
We study the M1.9-class solar flare SOL2015-09-27T10:40 UT using high-resolution full Stokes imaging spectropolarimetry of the Ca ii 8542 Å line obtained with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Within ten nearby (d < 450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
The heating of the Sun's chromosphere remains poorly understood. While progress has been made on understanding what drives the quiet-Sun internetwork chromosphere, chromospheric heating in strong magnetic field regions ...
(Master thesis / Masteroppgave, 2016)
Spherical collapse is a crude, but useful toy model for structure formation in an expanding universe. Previous works have looked at this model in ΛCDM with massive neutrinos, where the primary findings were that massive ...
(Doctoral thesis / Doktoravhandling, 2017)
(Doctoral thesis / Doktoravhandling, 2012)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Aims. We use state-of-the-art, three-dimensional non-local thermodynamic equilibrium (non-LTE) radiative magnetohydrodynamic simulations of the quiet solar atmosphere to carry out detailed tests of chromospheric magnetic ...
(Master thesis / Masteroppgave, 2022)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional ...
A DETAILED COMPARISON BETWEEN THE OBSERVED AND SYNTHESIZED PROPERTIES OF A SIMULATED TYPE II SPICULE
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
We have performed a three-dimensional radiative MHD simulation of the solar atmosphere. This simulation shows a jet-like feature that shows similarities to the type II spicules observed for the first time with Hinode's ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
The Mg II h&k lines are the prime chromospheric diagnostics of NASA's Interface Region Imaging Spectrograph (IRIS). In the previous papers of this series, we used a realistic three-dimensional radiative magnetohydrodynamics ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
Spicules have been observed on the Sun for more than a century, typically in chromospheric lines such as Hα and Ca II H. Recent work has shown that so-called "type II" spicules may have a role in providing mass to the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
The ionization state of the gas in the dynamic solar chromosphere can depart strongly from the instantaneous statistical equilibrium commonly assumed in numerical modeling. We improve on earlier simulations of the solar ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Context. The He i 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Context. While classical models successfully reproduce intensities of many transition region lines, they predict helium extreme-UV (EUV) line intensities roughly an order of magnitude lower than the observed value.
Aims. ...
(Doctoral thesis / Doktoravhandling, 2017)
(Master thesis / Masteroppgave, 2016)
If dark matter, after it has become non-relativistic, scatters elastically with a relativistic heat bath particle, then the resulting pressure leads to acoustic oscillations that suppress the growth of overdensities in the ...
(Doctoral thesis / Doktoravhandling, 2010)
(Master thesis / Masteroppgave, 2016)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
The quest for a B-mode imprint from primordial gravity waves on the polarization of the cosmic microwave background (CMB) requires the characterization of foreground polarization from Galactic dust. We present a statistical ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
The all-sky Planck survey in 9 frequency bands was used to search for emission from all 274 known Galactic supernova remnants. Of these, 16 were detected in at least two Planck frequencies. The radio-through-microwave ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
By looking at the kinetic Sunyaev-Zeldovich effect (kSZ) in Planck nominal mission data, we present a significant detection of baryons participating in large-scale bulk flows around central galaxies (CGs) at redshift z ≈ ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). We combine polarization data from Planck with ...
(Master thesis / Masteroppgave, 2016)
The Planck Sunyaev-Zeldovich Cluster catalogue provides an all-sky set of SZ detected galaxy clusters, which is the first of its kind. SZ signals are independent of redshift which allows a greater volume of space to be ...
(Master thesis / Masteroppgave, 2016)
(Doctoral thesis / Doktoravhandling, 2010)
(Doctoral thesis / Doktoravhandling, 2012)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
We present a description of the pipeline used to calibrate the Planck Low Frequency Instrument (LFI) timelines into thermodynamic temperatures for the Planck 2015 data release, covering four years of uninterrupted operations. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Parity-violating extensions of the standard electromagnetic theory cause in vacuo rotation of the plane of polarization of propagating photons. This effect, also known as cosmic birefringence, has an impact on the cosmic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
We have identified new clusters and characterized previously unknown Planck Sunyaev–Zeldovich (SZ) sources from the first Planck catalogue of SZ sources (PSZ1). The results presented here correspond to an optical follow-up ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
We present results from an observing campaign in support of the VAULT2.0 sounding rocket launch on 2014 September 30. VAULT2.0 is a Lyα (1216 Å) spectroheliograph capable of providing spectroheliograms at high cadence. Lyα ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(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 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© ESO, 2017
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
We report the identification of extended Lyα nebulae at z ≃ 3.3 in the Hubble Ultra Deep Field (HUDF, ≃40 kpc × 80 kpc) and behind the Hubble Frontier Field galaxy cluster MACSJ0416 (≃40 kpc), spatially associated with ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
Context. The solar coronal heating problem has been an open question in the science community since 1939. One of the proposed models for the transport and release of mechanical energy generated in the sub-photospheric ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© ESO, 2017
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
(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 / 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- ...
(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)
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 / 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, ...
(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 ...
SPATIAL VARIATIONS IN THE SPECTRAL INDEX OF POLARIZED SYNCHROTRON EMISSION IN THE 9 yr WMAP SKY MAPS
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We estimate the spectral index, β, of polarized synchrotron emission as observed in the 9 yr Wilkinson Microwave Anisotropy Probe sky maps using two methods, linear regression ("T-T plot") and maximum likelihood. We partition ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
© 2017. The American Astronomical Society. All rights reserved.
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2011)
Oscillations with periods on the order of 5–10 min have been observed by instrumented spacecrafts in the Earth's magnetosphere. These oscillations often follow sudden impacts related to coronal mass ejections. It is ...
(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 ...
(Doctoral thesis / Doktoravhandling, 2013)
(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 ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
A completely new mechanism to generate the observed amount of large-scale cosmological magnetic fields is introduced in the context of three-form inflation. The amplification of the fields occurs via fourth order dynamics ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
The Interface Region Imaging Spectrograph (IRIS) provides spectroscopy and narrow band slit-jaw (SJI) imaging of the solar chromosphere and transition region at unprecedented spatial and temporal resolutions. Combined with ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Aims: We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron, and f(R)-gravity models, we studied a phenomenological ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)
We present new high-resolution spectro-polarimetric Ca iiλ8542 observations of umbral flashes in sunspots. At nearly , and spanning about one hour of continuous observation, this is the most detailed dataset published thus ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)
Solar spicules are chromospheric fibrils that appear everywhere on the Sun, yet their origin is not understood. Using high resolution observations of spicules obtained with the Swedish 1 m Solar Telescope, we aim to ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We present a multi-level solver for drawing constrained Gaussian realizations or finding the maximum likelihood estimate of the cosmic microwave background sky, given noisy sky maps with partial sky coverage. The method ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
We measure [C iii] 1907, C iii] 1909 Å emission lines in 11 gravitationally lensed star-forming galaxies at z ~ 1.6–3, finding much lower equivalent widths than previously reported for fainter lensed galaxies. While it is ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Aims: We investigate the gravitational redshift in clusters of galaxies in the symmetron and Hu-Sawicky f(R) models. The characteristic feature of both models is the screening mechanism that hides the fifth force in dense ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
We present a novel approach to modified theories of gravity which consists of adding to the Einstein-Hilbert Lagrangian an f(R) term constructed à la Palatini. Using the respective dynamically equivalent scalar-tensor ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
The Gaussian kinematic formula (GKF) [R. J. Adler and J. E. Taylor, Random Fields and Geometry (Springer, New York, 2007).] is an extremely powerful tool allowing for explicit analytic predictions of expected values of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2011)
We investigate whether there is any cosmological evidence for a scalar field with a mass and coupling to matter which change accordingly to the properties of the astrophysical system it “lives in,” without directly focusing ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
In order to satisfy limits on the allowed variation of particle masses from big bang nucleosynthesis until today, the chameleon scalar field is required to reach its attractor solution early on in its cosmological evolution. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
We revisit the problem of exact cosmic microwave background (CMB) likelihood and power spectrum estimation with the goal of minimizing computational costs through linear compression. This idea was originally proposed for ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0farcs33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
Spectral observations of the solar transition region (TR) and corona show broadening of spectral lines beyond what is expected from thermal and instrumental broadening. The remaining non-thermal broadening is significant ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
In addition to primary fluctuations, cosmic microwave background (CMB) temperature maps contain a wealth of additional information in the form of secondary anisotropies. However, secondary effects that can be identified ...