Related papers: Extragalactic H3O+: Some Consequences
In a gravitationally unstable universe, the structure of dark matter and galaxies, intergalactic gas and magnetic field can have severe impact on the propagation of ultra high energy cosmic rays (UHECR) (Ryu & Kang, this proceedings). The…
If ultra-high-energy cosmic rays (UHECRs) have extragalactic origins, as is widely assumed to be the case at least for the majority of cosmic rays with energies above a few EeV, secondary neutrinos and photons can be expected to be produced…
The gamma-ray background is still a subject under great debate. All phenomena in the universe emitting gamma-rays can contribute directly as diffuse emission or as an isotropic component from unresolved point sources. The question of the…
I review recent observations of molecular gas in the halo of the Milky Way and in the Magellanic Clouds. Far-ultraviolet absorption line studies of molecular hydrogen (H_2) with ORFEUS and FUSE have unveiled the presence of a diffuse…
We review the physics of the highest energy cosmic rays. The discovery of their sources, still unknown, will reveal the most energetic astrophysical objects in the universe and could unveil new physics beyond the standard model of particle…
The decay of very heavy metastable relics of the Early Universe can produce ultra-high energy cosmic rays (UHECRs) in the halo of our own Galaxy. On distance scales of the order of the halo size, energy losses are negligible---no…
We present Galaxy Evolution Explorer (GALEX) images of the prototypical edge-on starburst galaxies M82 and NGC253. Our initial analysis is restricted to the complex of ultraviolet (UV) filaments in the starburst-driven outflows in the…
The search for the origin of cosmic rays is a quest of almost a hundred years. A recent theoretical proposal gives quantitative predictions, which can be tested with data. Specifically, it has been suggested, that all cosmic rays can be…
We report observations and an analysis of the distribution of HCO+(1-0) and HCO+(4-3) emission in the central 1 kpc star forming region of M82. Comparisons are made with other star formation indicators such as the mm continuum, the…
The origin of ultra-high energy cosmic rays is discussed in light of the latest observational results from the Pierre Auger Observatory, highlighting potential astrophysical sources such as active galactic nuclei, gamma-ray bursts, and…
In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction…
The quest for the origin(s) of ultra-high-energy cosmic rays (UHECRs) continues to be a far-reaching pillar of high energy astrophysics. The source scrutiny is mostly based on three observables: the energy spectrum, the nuclear composition,…
Possible existence of extragalactic ultra-high energy cosmic ray sources giving a very small particle flux on the Earth is considered. Accretion discs around supermassive black holes where particles are accelerated in electric fields are…
In this paper, we study the propagation of cosmic-ray nuclei and protons. We emphasize the influence of the source composition on the expected spectrum and composition on Earth as well as on the phenomenology of the transition from Galactic…
I review the assumptions and observations that motivate the concept of the extragalactic cosmic background radiation, and the issues of energy accounts and star formation history as a function of galaxy morphological type that figure in the…
By performing an orbital analysis within a Galactic model including a bar, we found that it is plausible that the newly discovered stars that show enhanced Al and N accompanied by Mg underabundances may have formed in the outer halo, or…
Neutral hydrogen clouds are found in the Milky Way and Andromeda halo both as large complexes and smaller isolated clouds. Here we present a search for Hi clouds in the halo of M33, the third spiral galaxy of the Local Group. We have used…
Study of extragalactic H2O masers has progressed significantly in the 25 years since their discovery. Existing in star forming regions and in the accretion disks supermassive black holes, they are familiar and unfamiliar at the same time. A…
Ultra-high energy cosmic rays are mostly charged particles and they are therefore deflected by magnetic fields on their path from their sources to Earth. An interesting phenomenon arising from these deflections is the appearance of multiple…
Interactions of cosmic rays with the interstellar gas and radiation fields of the Milky Way provide the majority of the gamma rays observed by the Fermi Gamma Ray Space Telescope. In addition to the gas which is densely concentrated along…