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Metal-poor (MP) stars in the Milky Way (the Galaxy) and its satellite galaxies open a window into the earliest times in the history of the Universe, probing the chemistry of the earliest times. Recent galaxy formation simulations predict that the oldest MP stars are those on tightly bound orbits in the inner regions of a galaxy (Tumlinson 2010). Applying this to the Milky Way, MP stars in the bulg
Nucleosynthesis is the mechanism which produces new elements in nuclear reactions. Nuclear reaction rates are highly temperature dependant, and nuclear reactions take place in very hot environments. Current theories predict that the light elements such as hydrogen and helium were produced during the Big Bang. On the other hand, the core of stars produce heavier elements through nuclear fusion. The
Context: The formation of the Galactic Bulge is a topic of active research. There are many scenarios based on observations and Galactic evolution models. The key properties which need to be well constrained observationally are the metallicity distributions of stars and the spatial metallicity gradients. The metallicity distribution of stars in the inner Galactic Bulge (|b|<4o) is a subject of ongo
A major avenue in the study of the Galaxy is the investigation of stellar populations and Galactic chemical evolution by stellar spectroscopy. Due to the dust obscuration in the line-of-sight, stars in the plane and toward the centre of the Galaxy can only be observed in the near-IR wavelength region. Important questions can thus be addressed by observing stars in the near-IR, a field that is in r
Context. Effective temperature is one of the fundamental stellar parameters. A traditional spectroscopic way to determine it is from optical spectra using excitation balance of Fe-lines. With technological advances and the advent of the next generation telescopes there will be an emphasis on the relatively unexplored near-IR (NIR) wavelength region (1-5 μm). A method to determine the effective tem
We investigate the radial infall of ice pebbles in a protoplanetary disk, and how these tend to end up in relatively close proximity to eachother, providing a possible spawning ground for planets. These pebbles have dust particles embedded in them, which are released as the pebble crosses the so-called ice- line, where the ice evaporates. This is interesting as the dust will pile up around this ic
In this thesis, I present a case where Dark Matter subhalos would annihilate at some stage in their lifetime. The implication of this scenario could potentially aid the Missing Satellites and the Cusp-Core density profile problem. The Dark Matter particles’ annihilation process and effective “friction” lead to an energy and momentum loss into radiation and hence to the destabilization of the Dark
Context: Data from the recently launched astrometric satellite Gaia will be coming in soon with the final data release expected in 2022. This will provide a very precise map of the Galaxy. The Solar system and Galaxy is thought to be filled with invisible bodies (planetesimals, planets, brown dwarfs, neutron stars, black holes, etc.) and they will affect the observations via gravitational lensing.
The origin of the class of exoplanets typically referred to as hot Jupiters is to this day an unsettled matter. Some of the proposed formation channels predict certain values of the spin-orbit misalignment parameter, i.e. the angle between the stellar rotation axis, and the angular momentum vector of the planet orbit. One such formation channel is tidal capture following Kozai resonance (TCKR). Th
Where the dust in a protoplanetary disk is as the disk evolves over time is essential to know for further studies of the planet formation process. A new star is created alongside a stellar nebula. The nebula contains rock, ice and gas which are not accreted to the star. Our nebula is constructed using the Minimum Mass Solar Nebula model and the column density is studied as the protoplanetary disk
This is an analysis of all the planets at exoplanets.org, with the goal of finding out how many of these that could possibly have moons supporting life. I have first calculated the ranges of the habitable zones (HZ:s) for the stars in the archive, using the Runaway Greenhouse model for the inner limit, and the Maximum Greenhouse model for the outer limit, as presented by Kopparapu et al. (2013A).
Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy. Aims. To study how well the Galactic matter distribution can be determin
Context. Intensity interferometry was invented and used by R.Hanbury Brown and R.Q.Twiss in the 1960's to measure stellar angular diameters. Its main advantage over conventional interferometry is that it enables very long baselines and is insensitive to poor seeing. However, because it requires very large light collectors, it was never pursued further. The Cherenkov Telescope Array (CTA) is a
In this thesis we add a temperature dependence to the newly developed variable polytrope equation of state (Varpoly EOS) from Weppner et al. (2015), making it more universal and more applicable for planetary simulations. In this process we develop a new model for the Gruneisen parameter, which is a parameter that describes how pressure changes with the internal energy. This new model conforms to t
For testing three-dimensional (3D) hydrodynamic models of stellar atmospheres, spectroscopy across spatially resolved stellar surfaces with high spectral resolution is desired. 3D models predict center-to-limb changes in asymmetries, shapes, strengths and wavelength positions of spectral line profiles, reflecting the hydrodynamics of the stellar atmosphere. However, except for a few supergiants an
In the thriving field of exoplanet research new discoveries are made all the time, and while most of the observed systems can be explained with classical planet formation models - some are much harder to explain. When stars form they are often surrounded by the remaining material of the nebulae they formed from. Some of this remaining material forms into a protoplanetary disk around the protostars
Star clusters can harbour many exotic objects, including black holes (BHs), X-ray binaries and blue straggler stars. In dense stellar environments like globular clusters (GCs), two-body relaxation drives their dynamical evolution, where gravitational interactions between stars strive to equalize their kinetic energy in the cluster. Theoretical studies have indicated that some of these clusters can
Context. The discovery of hot Jupiters, giant gas exoplanets on tight orbits close to their host star, has proven instrumental in the study of exoplanet atmospheres through transit spectroscopy. Just as a temperature increase with height manifests in Earth’s atmosphere due to ozone absorbing ultraviolet radiation, transit spectra of some hot Jupiters has yielded evidence that suggests the presence
Most of the things that we know about stars come from their spectrum. The properties of the atomic lines, e.g. energy levels, wavelengths, oscillator strengths, must be known to understand the observed spectrum and to perform quantitative analyses. Atomic data of some elements are incomplete, especially in the near-infrared region, which makes it difficult or even impossible to analyze a stellar s
Context. The formation and evolution of the Galactic bulge and the Milky Way is still a debated subject. Observations of, e.g., the X-shaped bulge, cylindrical stellar motions and young stars in the bulge have suggested that the bulge formed through secular evolution of the disk and not through gas dissipation and/or mergers, as thought previously.\\ Data. We use high-resolution optical spectra of
