Related papers: Cosmic rays cannot explain the high ionisation rat…
The Galactic center is the closest region in which we can study star formation under extreme physical conditions like those in high-redshift galaxies. We measure the temperature of the dense gas in the central molecular zone (CMZ) and…
Context. Recent observations of unexpected structures in the Galactic Cosmic Ray (GCR) spectrum and composition, as well as growing evidence for episodes of intense dynamical activity in the inner regions of the Galaxy, call for an…
The anomalous rate of molecules ionization observed at the Central Molecular zone (CMZ) challenges known mechanisms of ionization observed in molecular clouds across the Galaxy, due to the exceptionally high levels of ionization measured…
Cosmic-rays are the primary initiators of interstellar chemistry, and getting a better understanding of the varying impact they have on the chemistry of interstellar clouds throughout the Milky Way will not only expand our understanding of…
Molecular clouds act as targets for cosmic rays (CR), revealing their presence through either gamma-ray emission due to proton-proton interactions, and/or through the ionization level in the cloud, produced by the CR flux. The ionization…
We show that the secondary electrons ejected from the ionization of heavy ions can be injected into the acceleration process that occurs at supernova remnant shocks. This electron injection mechanism works since ions are ionized during the…
The Galactic centre - as the closest galactic nucleus - holds both intrinsic interest and possibly represents a useful analogue to star-burst nuclei which we can observe with orders of magnitude finer detail than these external systems. The…
The cosmic-ray ionization rate ($\zeta_2$) is one of the key parameters in star formation, since it regulates the chemical and dynamical evolution of molecular clouds by ionizing molecules and determining the coupling between the magnetic…
The ionization rate of interstellar material by cosmic rays has been a major source of controversy, with different estimates varying by three orders of magnitude. Observational constraints of this rate have all depended on analyzing the…
We have obtained high resolution FUSE and HST/STIS echelle observations of the quasar PG 1116+215. The semi-continuous coverage of the ultraviolet spectrum over the wavelength range 916-2800 provides detections of Galactic and high velocity…
The High Energy Stereoscopic System (HESS), the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope (MAGIC), and the Very Energetic Radiation Imaging Telescope Array System (VERITAS) have observed diffuse gamma-ray emission strongly…
Galactic cosmic-ray source compositions, (Z/H)GCRS from H to Pb and ~10^8 - 10^14 eV, differ from solar-local interstellar, (Z/H)SS or (Z/H)ISM by ~20-200x. Both are mostly just mixes of core collapse (CCSN) and thermonuclear (SN Ia)…
We revisit the idea that the Galactic center (GC) is the dominant source of Galactic cosmic rays (GCRs), based on a series of new observational evidence. A unified model is proposed to explain the new phenomena of GCRs and $\gamma$-rays…
The H.E.S.S. collaboration revealed the presence of a very high energy (VHE) diffuse emission in the inner 100pc of the Galaxy in close correlation with the Central Molecular Zone (CMZ). Recently, they deduced from this emission a…
At present, all physical models of diffuse Galactic gamma-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H2-rich regions…
A gamma-ray excess over background has been claimed in the inner regions of the Galaxy, triggering some excitement about the possibility that the gamma rays originate from the annihilation of dark matter particles. We point out that the…
It is presumed that the observed cosmic rays up to about $3\times 10^{18}$ eV are of Galactic origin, the particles being the ones which are found in the composition of the stellar winds of stars that explode as supernova into the…
The origin of Galactic cosmic rays (with energies up to 10^15 eV) remains unclear, though it is widely believed that they originate in the shock waves of expanding supernova remnants. Currently the best way to investigate their acceleration…
We explore the effects of the expected higher cosmic ray (CR) ionization rates $\zeta_{\rm CR}$ on the abundances of carbon monoxide (CO), atomic carbon (C), and ionized carbon (C$^+$) in the H$_2$ clouds of star-forming galaxies. The study…
Cosmic rays pervade the Galaxy and are thought to be accelerated in supernova shocks. The interaction of cosmic rays with dense interstellar matter has two important effects: 1) high energy (>1 GeV) protons produce {\gamma}-rays by…