Sökning: "Galaxy Clusters"

Visar resultat 1 - 5 av 31 avhandlingar innehållade orden Galaxy Clusters.

  1. 1. Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS

    Författare :Anders Pinzke; Lars Bergström; Olaf Reimer; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Galaxy clusters; gamma-rays; cosmic-rays; dark matter; High energy astrophysics; Högenergiastrofysik; teoretisk fysik; Theoretical Physics;

    Sammanfattning : The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. LÄS MER

  2. 2. Observations of nearby Galaxy Clusters with the Fermi Large Area Telescope : Towards the first Gamma Rays from Clusters

    Författare :Stephan Zimmer; Jan Conrad; Lars Bergström; Torsten Enßlin; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Galaxy Clusters; Fermi-LAT; γ rays; Dark Matter; Cosmic Rays; fysik; Physics;

    Sammanfattning : Galaxy clusters are the most massive bound systems known in the Universe and are believed to have formed through large scale structure formation. They host relativistic cosmic-ray (CR) populations and are gravitationally bound by large amounts of Dark Matter (DM), both providing conditions in which high-energy gamma rays may be produced either via CR interactions with the intracluster medium or through the annihilation or decay of DM particles. LÄS MER

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

    Författare :Cheng Liu; Astronomi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; 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

  4. 4. Searching for Gamma Rays from Galaxy Clusters with the Fermi Large Area Telescope : Cosmic Rays and Dark Matter

    Författare :Stephan Zimmer; Jan Conrad; Christophe Clement; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; galaxy clusters; gamma rays; cosmic rays; dark matter; fermi-lat; likelihood analysis; joint likelihood;

    Sammanfattning : In this licentiate thesis, I report a search for GeV γ rays towards the location of Galaxy clusters. I mainly discuss the results of a search for cosmic-ray (CR) induced γ-ray emission but also briefly elaborate on a related study, searching for Dark Matter (DM)-induced γ-ray emission from Galaxy clusters. LÄS MER

  5. 5. Clues to galaxy evolution from spectroscopic observations of Galactic centre stars

    Författare :Brian Thorsbro; Astronomi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Chemical abundances; Late-type stars; Star clusters; Galactic center; Galaxy chemical evolution; Chemical enrichment;

    Sammanfattning : In this work we present results from spectroscopic observations of Galactic centre stars. High resolution stellar spectroscopy can be used to determine accurate stellar metallicities and abundances. Observing stars in the Galactic centre is challenging due to extreme extinction. LÄS MER