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(Doctoral thesis / Doktoravhandling, 2024)
This thesis explores the Sun’s dynamic atmosphere, focusing on the role of accelerated particles. These particles are propelled to extremely high speeds during solar flares, which are bright, explosive events in the Sun’s ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
ABSTRACT
While proper orbital elements are currently available for more than 1 million asteroids, taxonomical information is still lagging behind. Surveys like SDSS-MOC4 provided preliminary information for more ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context . The Euclid mission of the European Space Agency will perform a survey of weak lensing cosmic shear and galaxy clustering in order to constrain cosmological models and fundamental physics.
Aims . We expand and ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
ABSTRACT
The study of stellar flares has increased with new observations from CoRoT, Kepler, and TESS satellites, revealing the broad-band visible emission from these events. Typically, stellar flares have been ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. Oscillations are observed to be pervasive throughout the solar corona, but it remains challenging to positively identify different wave modes. Improving this identification would provide a powerful tool for ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
Three-minute oscillations are a common phenomenon in the solar chromosphere above a sunspot. Oscillations can be affected by the energy release process related to solar flares. In this paper, we report ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. The cosmological surveys that are planned for the current decade will provide us with unparalleled observations of the distribution of galaxies on cosmic scales, by means of which we can probe the underlying ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
The technique of photometric redshifts has become essential for the exploitation of multi-band extragalactic surveys. While the requirements on photometric redshifts for the study of galaxy evolution mostly pertain to the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
ABSTRACT
We have used the Ultraviolet Imaging Telescope (UVIT) aboard AstroSat to study star formation in a sample of nine dual nuclei galaxies with separations ⪅ 11 kpc, which is an expected outcome of galaxy ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. Synthetic spectra from 3D models of the solar atmosphere have become increasingly successful at reproducing observations, but there are still some outstanding discrepancies for chromospheric spectral lines, such ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Forthcoming imaging surveys will increase the number of known galaxy-scale strong lenses by several orders of magnitude. For this to happen, images of billions of galaxies will have to be inspected to identify potential ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
We present six strongly gravitationally lensed Ly α emitters (LAEs) at z ∼ 4–5 with Hubble Space Telescope (HST) narrowband imaging isolating Lyα. Through complex radiative transfer Lyα encodes information about the spatial ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. The properties of pre-eruptive structures and coronal mass ejections (CMEs) are characterized by those of their footpoints, the latter of which attract a great deal of interest. However, the matter of how to ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
ABSTRACT
We present trevr2 (Tree-based REVerse Ray Tracing 2), a fast, general algorithm for computing the radiation field, suitable for both particle and mesh codes. It is designed to self-consistently evolve ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
We use time-domain simulations of Jupiter observations to test and develop a beam reconstruction pipeline for the Simons Observatory Small Aperture Telescopes. The method relies on a mapmaker that estimates ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
We present a cross-correlation analysis between 1´resolution total intensity and polarization observations from the Atacama Cosmology Telescope (ACT) at 150 and 220 GHz and 15'' mid-infrared photometry from the Wide-field ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
To obtain an accurate cosmological inference from upcoming weak lensing surveys such as the one conducted by Euclid , the shear measurement requires calibration using galaxy image simulations. As it typically requires ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
With two central galaxies engaged in a major merger and a remarkable chain of 19 young stellar superclusters wound around them in projection, the galaxy cluster SDSS J1531+3414 (z = 0.335) offers an excellent laboratory ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Aims. We validate a semi-analytical model for the covariance of the real-space two-point correlation function of galaxy clusters.
Methods. Using 1000 PINOCCHIO light cones mimicking the expected Euclid sample of galaxy ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon known as Ellerman bombs (EBs). It is most common to observe EBs in the H α and H β ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
(Doctoral thesis / Doktoravhandling, 2024)
In my thesis, I investigated local (ultra-)luminous infrared galaxies, typically identified as galaxy mergers. These galaxies are fascinating due to their intense star formation and active galactic nuclei, which can lead ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
The very outer solar atmosphere (corona) is very hot with temperatures over a million degrees K, while the photosphere is of the order of 5000 K. Embedded in this hot outer corona are cool, QUOTE ≤ 10,000 K, magnetic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
Redshift measurements, primarily obtained from host galaxies, are essential for inferring cosmological parameters from type Ia supernovae (SNe Ia). Matching SNe to host galaxies using images is nontrivial, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. Plasmoid-mediated reconnection plays a fundamental role in different solar atmospheric phenomena. Numerical reproduction of this process is therefore essential for developing robust solar models.
Aims. Our goal ...
Chromospheric and coronal heating in an active region plage by dissipation of currents from braiding
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract The question of what heats the outer solar atmosphere remains one of the longstanding mysteries in astrophysics. Statistical studies of Sun-like stars reveal a correlation between global chromospheric and coronal ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
We present the most comprehensive collection of stratified-in-optical-depth thermodynamic models of the lower solar atmosphere. This database, named IRIS 2+ , consists of 40,320 synthetic representative ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
Small-scale, newly emerging internetwork (IN) magnetic fields are considered a viable source of energy and mass for the solar chromosphere and possibly the corona. Multiple studies show that single events ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
We compare two different numerical methods to integrate in time spatially delocalized initial densities using the Schrödinger-Poisson equation system as the evolution law. The basic equation is a nonlinear Schrödinger ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Modified gravity models with scale-dependent linear growth typically exhibit an enhancement in the power spectrum beyond a certain scale. The conventional methods for extracting cosmological information usually involve ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Abstract
We present fluxes and light curves for a population of asteroids at millimeter wavelengths, detected by the Atacama Cosmology Telescope (ACT) over 18,000 deg 2 of the sky using data from 2017 to 2021. ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
Context. Charged particles are constantly accelerated to non-thermal energies by the reconnecting magnetic field in the solar atmosphere. Our understanding of the interactions between the accelerated particles and their ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
(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, 2023)
The theoretical basis of dark energy remains unknown and could signify a need to modify the laws of gravity on cosmological scales. In this study, we investigate how the clustering and motions of galaxies can be used as ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
ABSTRACT We present the deconvolved distribution estimator (DDE), an extension of the voxel intensity distribution (VID), in the context of future observations proposed as part of the CO Mapping Array Project (COMAP). The ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. Nanoflare heating through small-scale magnetic reconnection events is one of the prime candidates to explain heating of the solar corona. However, direct signatures of nanoflares are difficult to determine, and ...
(Doctoral thesis / Doktoravhandling, 2023)
Understanding the mechanisms responsible for heating the solar atmosphere from a few thousand Kelvin in the photosphere to millions of degrees in the corona is a major challenge in solar physics. A number of potential ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The Euclid mission will conduct an extragalactic survey over 15 000 deg 2 of the extragalactic sky. The spectroscopic channel of the Near-Infrared Spectrometer and Photometer (NISP) has a resolution of R ~ 450 for its blue ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Local primordial non-Gaussianity (PNG) is a promising observable of the underlying physics of inflation, characterized by flocNL. We present the methodology to measure flocNL from the Dark Energy Survey (DES) data using ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. The intensity of radiation from the solar atmosphere at millimetre wavelengths is closely related to the plasma temperature, and the formation height of the radiation is wavelength dependent. It follows from this ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. The solar atmosphere is highly dynamic, and observing the small-scale features is valuable for interpretations of the underlying physical processes. The contrasts and magnitude of the observable signatures of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The Square Kilometre Array Observatory (SKAO) is perhaps the most ambitious radio telescope envisaged yet. It will enable unprecedented studies of the Sun, corona and heliosphere and help to answer many of the outstanding ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Waves and oscillations have been observed in the Sun’s atmosphere for over half a century. While such phenomena have readily been observed across the entire electromagnetic spectrum, spanning radio to gamma-ray sources, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Master thesis / Masteroppgave, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. The shapes of Stokes profiles contain a great deal of information about the atmospheric conditions that produced them. However, a variety of different atmospheric structures can produce very similar profiles. Thus, ...
(Doctoral thesis / Doktoravhandling, 2023)
The oldest radiation in the universe is the Cosmic Microwave Background (CMB) radiation. Analysing the CMB is like analysing a baby picture of the Universe, and gives us unique information on what the Universe looked like ...
(Doctoral thesis / Doktoravhandling, 2023)
The study of the cosmic microwave background (CMB) radiation is a pillar of modern cosmology that enables us to understand the history, the evolution of structures, and the global shape (topology) of the Universe. This ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. Next-generation wide-field optical polarimeters such as Wide-Area Linear Optical Polarimeters (WALOPs) have a field of view (FoV) of tens of arcminutes. Wide-field polarimetric flat sources are essential to the ...
(Chapter / Bokkapittel / PublishedVersion; Peer reviewed, 2023)
The Lambda-Cold Dark Matter (ΛCDM) model agrees with most of the cosmological observations, but has some hindrances from observed data at smaller scales such as galaxies. Recently, Berezhiani and Khoury proposed a new ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Tension between cosmic microwave background–based and distance ladder–based determinations of the Hubble constant H0 motivates the pursuit of independent methods that are not subject to the same systematic effects. A ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The Gaia Multipeak (GMP) technique can be used to identify large numbers of dual or lensed active galactic nucleus (AGN) candidates at subarcsec separation, allowing us to study both multiple supermassive black holes (SMBHs) ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
We present C OSMOGLOBE Data Release 1, which implements the first joint analysis of WMAP and Planck LFI time-ordered data, processed within a single Bayesian end-to-end framework. This framework directly builds on a similar ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Doctoral thesis / Doktoravhandling, 2023)
Massive neutrinos and alternative theories of gravity are two seemingly different aspects of cosmological study. On one hand, we have actual particles known to exist, and on the other, a proposed change to the description ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
The dynamic atmosphere imposes challenges to ground-based cosmic microwave background observation, especially for measurements on large angular scales. The hydrometeors in the atmosphere, mostly in the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. The non-Gaussian Cold Spot surrounded by its hot ring is one of the most striking features of the cosmic microwave background (CMB) and has generated significant attention in the literature. It has been speculated ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
We report on the disk-averaged absolute brightness temperatures of Venus measured at four microwave frequency bands with the Cosmology Large Angular Scale Surveyor. We measure temperatures of 432.3 ± ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
The O i 1355 Å spectral line is one of the only optically thin lines that are both routinely observed and thought to be formed in the chromosphere. We present an analysis of a variety of observations of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
We perform a search for galaxy–galaxy strong lens systems using a convolutional neural network (CNN) applied to imaging data from the first public data release of the DECam Local Volume Exploration Survey, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
The solar atmosphere is filled with clusters of hot small-scale loops commonly known as coronal bright points (CBPs). These ubiquitous structures stand out in the Sun by their strong X-ray and/or ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The ultra-faint dwarf galaxy Reticulum II (Ret II) exhibits a unique chemical evolution history, with
% of its stars strongly enhanced in r-process elements. We present deep Hubble Space Telescope photometry of Ret II and ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Aims. We analyse the signature and origin of transient structures embedded in the slow solar wind, and observed by the Wide-Field Imager for Parker Solar Probe (WISPR) during its first ten passages close to the Sun. WISPR ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
ABSTRACT
Understanding the physical processes that trigger solar flares is paramount to help with forecasting space weather and mitigating the effects on our technological infrastructure. A previously unknown ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
Coronal mass ejections are explosive plasma phenomena prevalently occurring on the Sun and probably on other magnetically active stars. However, how their pre-eruptive configuration evolves toward the ...
(Doctoral thesis / Doktoravhandling, 2023)
The cosmic microwave background (CMB) is not just the oldest light in the Universe but also the oldest polarized light. By measuring its patterns, we can learn large amounts of information about the origin of the Universe ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
We combine photometry of Eris from a 6 month campaign on the Palomar 60 inch telescope in 2015, a 1 month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013–2018 to ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
We have investigated the cosmological constraints that can be expected from measurement of the cross-correlation of galaxies with cosmic voids identified in the Euclid spectroscopic survey, which will include spectroscopic ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The measurement of the absolute neutrino mass scale from cosmological large-scale clustering data is one of the key science goals of the Euclid mission. Such a measurement relies on precise modelling of the impact of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
Magnetic field plays an important role in various solar eruption phenomena. The formation and evolution of the characteristic magnetic field topology in solar eruptions are critical problems that will ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
In most cosmological models, the equation of state of the dark matter is assumed to be zero, which means that the dark matter is pressure-less or cold. While this hypothesis is based on the abundance of ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The BeyondPlanck and Cosmoglobe collaborations have implemented the first integrated Bayesian end-to-end analysis pipeline for CMB experiments. The primary long-term motivation for this work is to develop a common analysis ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
ABSTRACT
We present the first systematic follow-up of Planck Sunyaev–Zeldovich effect (SZE) selected candidates down to signal-to-noise (S/N) of 3 over the 5000 deg2 covered by the Dark Energy Survey. Using the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
Extreme, young stellar populations are considered to be the primary contributor to cosmic reionization. How the Lyman continuum (LyC) escapes these galaxies remains highly elusive, and it is challenging ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
The gravitational lens system PS J0147+4630 (Andromeda’s Parachute) consists of four quasar images ABCD and a lensing galaxy. We obtained r -band light curves of ABCD in the 2017−2022 period from monitoring with two 2 m ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
Gravitationally lensed supernovae (LSNe) are important probes of cosmic expansion, but they remain rare and difficult to find. Current cosmic surveys likely contain 5–10 LSNe in total while next-generation ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2 April 2022, an M-class flare followed by a filament eruption was seen both by the instruments on board ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. Oscillations are abundant in the solar corona. Coronal loop oscillations are typically studied using highly idealised models of magnetic flux tubes. In order to improve our understanding of coronal oscillations, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Study Analysis Group 21 (SAG21) of NASA’s Exoplanet Exploration Program Analysis Group was organized to study the effect of stellar contamination on space-based transmission spectroscopy, a method for studying exoplanetary ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
High-resolution spectral observations of the lower solar atmosphere (chromosphere and transition region) during coronal heating events, in combination with predictions from models of impulsively heated ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Understanding the nature of high-redshift dusty galaxies requires a comprehensive view of their interstellar medium (ISM) and molecular complexity. However, the molecular ISM at high redshifts is commonly studied using ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
ABSTRACT
We measure the impact of source galaxy clustering on higher order summary statistics of weak gravitational lensing data. By comparing simulated data with galaxies that either trace or do not trace the ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
ABSTRACT
We present an alternative calibration of the MagLim lens sample redshift distributions from the Dark Energy Survey (DES) first 3 yr of data (Y3). The new calibration is based on a combination of a ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Particle acceleration is a fundamental process arising in many astrophysical objects, including active galactic nuclei, black holes, neutron stars, gamma-ray bursts, accretion disks, solar and stellar coronae, and planetary ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Abstract
We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. Type Ia supernovae (SNe Ia) are useful distance indicators in cosmology, provided their luminosity is standardized by applying empirical corrections based on light-curve properties. One factor behind these corrections ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
Context. A new and hitherto unknown cosmic microwave background (CMB) foreground has recently been detected. A systematic decrease in CMB temperatures around nearby large spiral galaxies points to an unknown interaction ...
(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
(Chapter / Bokkapittel / PublishedVersion; Peer reviewed, 2023)
The Atacama Large Aperture Submillimeter Telescope (At- LAST) aims to be the premier next generation large diameter (50 meter) single dish observatory capable of observations across the millimeter/submillimeter spectrum, ...