Sökning: "chemical abundances"

Visar resultat 11 - 15 av 51 avhandlingar innehållade orden chemical abundances.

  1. 11. A study of possible chemical inhomogeneities of dwarf irregular galaxies and the influence on the Z-L relationship

    Författare :Ana Maria Hidalgo-Gámez; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; dwarf irregular galaxies; chemical abundances; metallicity-luminosity relationship; individual galaxies: NGC 6822; IC 4662; IC 10; ESO 245-G05; NGC 1569; IC 5152; DDO 53 and DDO 190; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Sammanfattning : A study on the chemical abundances of dwarf irregular galaxies (dI's) is presented in this work. This type of galaxies have typically low metallicity. First of all, a definition of dI is proposed, in order to obtain a homogeneous group of targets. LÄS MER

  3. 12. Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy

    Författare :Karin Jonsell; Bengt Gustafsson; Bengt Edvardsson; Paul Barklem; Christopher Sneden; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Astronomy; Galactic evolution; Halo; Milky Way; Oxygen; r-element; s-element; Stellar abundances; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. LÄS MER

  4. 13. Asymptotic Giant Branch stars viewed up-close and far-off : The physics, chemistry, and evolution of their circumstellar envelopes

    Författare :Matthias Maercker; Hans Olofsson; Fredrik L. Schöier; Laurentius B. F. M. Waters; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; AGB stars; evolution; mass-loss; abundances; Astronomy; Astronomi; Astronomy; astronomi;

    Sammanfattning : The asymptotic giant branch (AGB) is the last stage of stellar evolution for stars with masses between 0.8-8 M(sun). This phase is characterised by an intense mass loss, which builds up a circumstellar envelope of dust and gas(CSE). It is through this process that the AGB stars contribute to the chemical evolution of galaxies. LÄS MER

  5. 14. The cosmic origin of fluorine and sulphur: Infrared spectroscopic studies of red giants

    Författare :Henrik Jönsson; Astronomi - Genomgår omorganisation; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Chemical evolution; near-infrared and mid-infrared spectroscopy; stellar abundances;

    Sammanfattning : Disregarding the small primordial traces of the lightest elements, all metals have been formed in stellar processes, which means that the relative amount of metals in the Universe increases for every stellar generation. This build-up of elements is called chemical evolution and might be used both to constrain stellar models as well as understanding the formation and evolution of stellar populations. LÄS MER

  7. 15. The nature of stars with a common origin: clues from metallicity, elemental abundances, and kinematics

    Författare :Cheng Liu; Astronomi - Genomgår omorganisation; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stars: abundances; Galaxy: evolution; Galaxy: solar neighbourhood; Galaxy: bulge; Galaxy: globular clusters;

    Sammanfattning : Most of field stars originate from dissolved star clusters. If the gas cloud is well mixed the stars in the cluster are expected to be chemically homogenous. LÄS MER