scholarly journals The cycling of carbon into and out of dust

2014 ◽  
Vol 168 ◽  
pp. 313-326 ◽  
Author(s):  
Anthony P. Jones ◽  
Nathalie Ysard ◽  
Melanie Köhler ◽  
Lapo Fanciullo ◽  
Marco Bocchio ◽  
...  
Keyword(s):  
Optical Properties ◽  
Cosmic Rays ◽  
Shock Waves ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Molecular Clouds ◽  
Observational Evidence ◽  
Electron Collisions ◽  
Uv Photons ◽  
Dust Evolution

Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are processed in photo-dissociation regions by UV photons, by ion and electron collisions in interstellar shock waves and by cosmic rays. A significant fraction of hydrocarbon dust must therefore be re-formed by accretion in the dense, molecular ISM. A new dust model (Jones et al., Astron. Astrophys., 2013, 558, A62) shows that variations in the dust observables in the diffuse interstellar medium (nH ≤ 103 cm−3), can be explained by systematic and environmentally-driven changes in the small hydrocarbon grain population. Here we explore the consequences of gas-phase carbon accretion onto the surfaces of grains in the transition regions between the diffuse ISM and molecular clouds (e.g., Jones, Astron. Astrophys., 2013, 555, A39). We find that significant carbonaceous dust re-processing and/or mantle accretion can occur in the outer regions of molecular clouds and that this dust will have significantly different optical properties from the dust in the adjacent diffuse ISM. We conclude that the (re-)processing and cycling of carbon into and out of dust is perhaps the key to advancing our understanding of dust evolution in the ISM.

scholarly journals The efficiency of grain growth in the diffuse interstellar medium

2021 ◽  
Vol 502 (2) ◽  
pp. 2438-2445
Author(s):  
F D Priestley ◽  
I De Looze ◽  
M J Barlow
Keyword(s):  
Interstellar Medium ◽  
Size Distribution ◽  
Gas Phase ◽  
Grain Growth ◽  
Common Assumption ◽  
Small Grains ◽  
Far Ultraviolet ◽  
Dust Evolution ◽  
Charged Ions ◽  
Positively Charged

ABSTRACT Grain growth by accretion of gas-phase metals is a common assumption in models of dust evolution, but in dense gas, where the time-scale is short enough for accretion to be effective, material is accreted in the form of ice mantles rather than adding to the refractory grain mass. It has been suggested that negatively charged small grains in the diffuse interstellar medium (ISM) can accrete efficiently due to the Coulomb attraction of positively-charged ions, avoiding this issue. We show that this inevitably results in the growth of the small-grain radii until they become positively charged, at which point further growth is effectively halted. The resulting gas-phase depletions under diffuse ISM conditions are significantly overestimated when a constant grain size distribution is assumed. While observed depletions can be reproduced by changing the initial size distribution or assuming highly efficient grain shattering, both options result in unrealistic levels of far-ultraviolet extinction. We suggest that the observed elemental depletions in the diffuse ISM are better explained by higher initial depletions, combined with inefficient dust destruction by supernovae at moderate ($n_{\rm H}\sim 30 \, {\rm cm}^{-3}$) densities, rather than by higher accretion efficiences.

scholarly journals Fermi LAT study of cosmic-rays and the interstellar medium in nearby molecular clouds

2013 ◽  
Author(s):  
Katsuhiro Hayashi ◽  
Tsunefumi Mizuno ◽  
Fermi-LAT Collaboration
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Molecular Clouds

scholarly journals Irradiation effects in CO and CO2 ices induced by swift heavy Ni ions at 46 MeV and 537 MeV

2009 ◽  
Vol 5 (S265) ◽  
pp. 428-429
Author(s):  
A. Domaracka ◽  
E. Seperuelo Duarte ◽  
P. Boduch ◽  
H. Rothard ◽  
E. Balanzat ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Gas Phase ◽  
Heavy Ions ◽  
Heavy Ion ◽  
Electronic Energy ◽  
Irradiation Effects ◽  
Nickel Ions ◽  
Sputtering Yield ◽  
Uv Photons ◽  
Fe Ions

AbstractIn order to simulate the effects of the heavy ion component of cosmic rays on ices in astrophysical environments, the CO and CO2 ices were irradiated with swift nickel ions in the electronic energy loss regime. The ices were prepared by condensing gas onto a CsI substrate at a temperature of 14 K and analyzed by means of infrared (FTIR) spectroscopy. The physical process of deposition by Ni ions is similar to more important and abundant heavy cosmic rays such as Fe ions. Dissociation of the ice molecules, and formation of new molecules were observed. Also, sputtering (leading to desorption of molecules from the solid surface to the gas phase) was observed. It was found that the sputtering yield due to heavy ions cannot be neglected with respect to desorption induced by weakly ionizing particles such as UV photons and protons.

scholarly journals QUANTIFYING THE INTERSTELLAR MEDIUM AND COSMIC RAYS IN THE MBM 53, 54, AND 55 MOLECULAR CLOUDS AND THE PEGASUS LOOP USINGFERMI-LAT GAMMA-RAY OBSERVATIONS

2016 ◽  
Vol 833 (2) ◽  
pp. 278 ◽  
Author(s):  
T. Mizuno ◽  
S. Abdollahi ◽  
Y. Fukui ◽  
K. Hayashi ◽  
A. Okumura ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Gamma Ray

scholarly journals Cosmic-Ray Injection into Shock-Waves

1981 ◽  
Vol 94 ◽  
pp. 361-362 ◽  
Author(s):  
Catherine J. Cesarsky ◽  
Jean-Pierre Bibring
Keyword(s):  
Cosmic Rays ◽  
Shock Waves ◽  
Interstellar Medium ◽  
Ionization Potential ◽  
Absorption Line ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Reactive Elements ◽  
Refractory Elements ◽  
First Ionization Potential

When corrected for the effects of propagation in the interstellar medium (i.s.m.), the observed composition of galactic cosmic rays can give us some clues as to the origin of these particles. It is noteworthy that the main pecularities of the cosmic ray source composition (CRS), as compared to normal i.s.m. abundances, bear some resemblance to that of i.s. grains, as inferred from i.s. absorption line measurements (e.g. York 1976): (1) the refractory elements Al, Si, Mg, Ni, Fe and Ca, which in i.s. clouds are almost completely locked into grains, are present with normal abundance ratios in the CRS. (2) normalized to Si, the volatile and reactive elements C, N, O, S and Zn are underabundant in CRS by factors of 2.5 to 6; these elements are only partially depleted in the i.s.m. (3) at a given rigidity the ratios H/Si and He/Si are lower than in the i.s.m. by a factor of ~ 25; while H and He atoms are virtually absent in i.s. grains. (1) implies that cosmic rays originate in astrophysical sites where the grains have either not condensated as yet, or where they have been (at least partially) destroyed. Then, to account for (2) and (3), one might consider that an unspecified mechanism selects the particles to be accelerated, possibly according to their first ionization potential (Cassé 1979 and references there-in).

scholarly journals Turbulence in the interstellar medium

2014 ◽  
Vol 21 (3) ◽  
pp. 587-604 ◽  
Author(s):  
D. Falceta-Gonçalves ◽  
G. Kowal ◽  
E. Falgarone ◽  
A. C.-L. Chian
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Interstellar Medium ◽  
Turbulent Flows ◽  
Molecular Clouds ◽  
Three Dimensional ◽  
Interstellar Turbulence ◽  
The Stability ◽  
Observational Techniques ◽  
And Diffusion

Abstract. Turbulence is ubiquitous in the insterstellar medium and plays a major role in several processes such as the formation of dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, and the re-acceleration and diffusion of cosmic rays. Despite its importance, interstellar turbulence, like turbulence in general, is far from being fully understood. In this review we present the basics of turbulence physics, focusing on the statistics of its structure and energy cascade. We explore the physics of compressible and incompressible turbulent flows, as well as magnetised cases. The most relevant observational techniques that provide quantitative insights into interstellar turbulence are also presented. We also discuss the main difficulties in developing a three-dimensional view of interstellar turbulence from these observations. Finally, we briefly present what the main sources of turbulence in the interstellar medium could be.

scholarly journals On the Nature of Magnetohydrodynamic Turbulence in the Interstellar Medium

1990 ◽  
Vol 140 ◽  
pp. 153-154
Author(s):  
V.N. Fedorenko
Keyword(s):  
Cosmic Rays ◽  
Shock Waves ◽  
Interstellar Medium ◽  
Weak Shock ◽  
Mhd Waves ◽  
Mhd Turbulence ◽  
Magnetohydrodynamic Turbulence ◽  
Extended Spectrum

Various mechanisms of creation of the extended spectrum of MHD turbulence in the interstellar medium are reviewed. Within the scales 1014 cm ≲ L ≲ 1019 cm the turbulence mostly consists of the ensemble of weak shock waves. At 1012 cm ≲ L ≲ 1014 cm the principle mechanism is generation of MHD waves by cosmic rays.

scholarly journals Interaction of escaping cosmic rays with molecular clouds

2013 ◽  
Vol 9 (S296) ◽  
pp. 320-327
Author(s):  
Stefano Gabici
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Present Status ◽  
Molecular Clouds ◽  
Gamma Ray ◽  
The Way

AbstractThe study of the gamma–ray radiation produced by cosmic rays that escape their accelerators is of paramount importance for (at least) two reasons: first, the detection of those gamma–ray photons can serve to identify the sources of cosmic rays and, second, the characteristics of that radiation give us constraints on the way in which cosmic rays propagate in the interstellar medium. This paper reviews the present status of the field.

scholarly journals FERMILARGE AREA TELESCOPE STUDY OF COSMIC RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS

2012 ◽  
Vol 755 (1) ◽  
pp. 22 ◽  
Author(s):  
M. Ackermann ◽  
M. Ajello ◽  
A. Allafort ◽  
L. Baldini ◽  
J. Ballet ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Molecular Clouds

scholarly journals ERRATUM: “FERMI LARGE AREA TELESCOPE STUDY OF COSMIC-RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS” (2012, ApJ, 755, 22)

2013 ◽  
Vol 778 (1) ◽  
pp. 82 ◽  
Author(s):  
M. Ackermann ◽  
M. Ajello ◽  
A. Allafort ◽  
L. Baldini ◽  
J. Ballet ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Large Area
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