Sökning: "Hans Olofsson"

Visar resultat 6 - 10 av 11 avhandlingar innehållade orden Hans Olofsson.

  1. 6. Molecular gas in the galaxy M83 : Its distribution, kinematics, and relation to star formation

    Författare :Andreas Andersson Lundgren; Hans Olofsson; John Whiteoak; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Molecular gas; Galaxies; Galaxies individual: M83; Star formation; Galactic dynamics; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : The barred spiral galaxy M83 (NGC5236) has been observed in the 12CO J=1–0 and J=2–1 millimetre lines with the Swedish-ESO Submillimetre Telescope (SEST). The sizes of the CO maps are 100×100, and they cover the entire optical disk. The CO emission is strongly peaked toward the nucleus. LÄS MER

  3. 7. Long-lasting ecological legacies of reindeer on tundra vegetation

    Författare :Dagmar D. Egelkraut; Johan Olofsson; Bruce Forbes; Hans Tømmervik; René van der Wal; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Alternative stable state; Herbivory; Historical contingency; Nutrient cycling; Plant-herbivore interactions; Plant-soil feedbacks; Rangifer tarandus; Reindeer herding; Traditional land use; Tundra vegetation;

    Sammanfattning : Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. LÄS MER

  4. 8. Stellar Winds of Cool Giants : Investigating the Mass-Loss Mechanism of AGB Stars

    Författare :Sofie Liljegren; Susanne Höfner; Kjell Eriksson; Bernd Freytag; Hans Olofsson; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; late-type stars; AGB stars; stellar winds; stellar atmospheres; dust; stellar pulsation; hydrodynamics; radiative transfer;

    Sammanfattning : Asymptotic giant branch (AGB) stars are luminous cool giants of low to intermediate mass that are strongly pulsating and non-spherical, with heavy mass loss through a stellar wind. The mass loss makes these stars important for galactic chemistry, as the wind enriches the interstellar medium with new elements and dust, and it determines the final fate of these stars. LÄS MER

  5. 9. 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

  7. 10. Molecules and Dust around AGB stars : Mass-loss rates and molecular abundances

    Författare :Sofia Ramstedt; Hans Olofsson; Fredrik Schöier; José Cernicharo; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; AGB stars; mass-loss; circumstellar abundances; Formation and development of stars; Stjärnors bildning och utveckling; Astronomy; astronomi;

    Sammanfattning : All stars with a stellar mass of about 0.8–8 MSun will end their lives as asymptotic giant branch (AGB) stars. Through their extensive mass loss the AGB stars constitutes an important source of nuclear processed material. LÄS MER