Results 21 to 30 of about 42,847 (320)
The Transition from Diffuse Molecular Gas to Molecular Cloud Material in Taurus [PDF]
The Astrophysical Journal, 2021 Abstract We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical conditions toward stars behind the Taurus Molecular Cloud (TMC).
S. R. Federman +8 more
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The Astrophysical JournalNewly computed collisional rate coefficients for the excitation of C _2 in collisions with H _2 , presented recently by Najar & Kalugina, are significantly larger than the values adopted previously in models for the excitation of the C _2 molecule, a ...
David A. Neufeld +9 more
doaj +2 more sources
Penetration of Cosmic Rays into Dense Molecular Clouds: Role of Diffuse Envelopes∗ [PDF]
The Astrophysical Journal, 2018 Abstract A flux of cosmic rays (CRs) propagating through a diffuse ionized gas can excite MHD waves, thus generating magnetic disturbances. We propose a generic model of CR penetration into molecular clouds through their diffuse envelopes, and identify the leading physical processes controlling their transport on the way from a highly ...
A. V. Ivlev +5 more
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Magnetic Fields in Diffuse HI and Molecular Clouds [PDF]
, 2007 50 pages, 14 figures, to be published as book chapter in 'Cosmic Magnetic Fields'
Carl Heiles, R. M. Crutcher
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Origin of CH+ in diffuse molecular clouds [PDF]
Astronomy & Astrophysics, 2016 Context. Molecular clouds are known to be magnetised and to display a turbulent and complex structure where warm and cold phases are interwoven. The turbulent motions within molecular clouds transport molecules, and the presence of magnetic fields induces a relative velocity between neutrals and ions known as the ion-neutral drift (vd).
Valeska Valdivia +5 more
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Formation of Dust Filaments in the Diffuse Envelopes of Molecular Clouds [PDF]
The Astrophysical Journal, 2021 Abstract The path to understanding star formation processes begins with the study of the formation of molecular clouds. The outskirts of these clouds are characterized by low column densities that allow the penetration of ultraviolet radiation, resulting in a nonnegligible ionization fraction and the charging of the small dust grains ...
Leire Beitia-Antero +2 more
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Diffuse interstellar medium and the formation of molecular clouds [PDF]
, 2007 (Abridged) The formation of molecular clouds (MCs) from the diffuse interstellar gas appears to be a necessary step for star formation, as young stars invariably occur within them. However, the mechanisms controlling the formation of MCs remain controversial.
P. Hennebelle +2 more
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Diffusive versus Free-streaming Cosmic-Ray Transport in Molecular Clouds [PDF]
The Astrophysical Journal, 2019 Abstract Understanding the cosmic-ray (CR) ionization rate is crucial in order to simulate the dynamics of molecular clouds, and interpret the chemical species observed in these objects. Calculating the CR ionization rate requires both accurate knowledge of the spectrum of MeV to GeV protons at the edge of the cloud as well as a model ...
Kedron Silsbee, A. V. Ivlev
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Optical Observations related to the Molecular Chemistry in Diffuse Interstellar Clouds [PDF]
Symposium - International Astronomical Union, 1987 Observations, which have been published since 1979, of molecular species in diffuse clouds will be discussed. Particular attention will be given to the ultraviolet measurements of CO with the Copernicus and IUE satellites and to ground-based optical measurements of CH, CH+, CN, and C2.
S. R. Federman
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The Behavior of Selected Diffuse Interstellar Bands with Molecular Fraction in Diffuse Atomic and Molecular Clouds [PDF]
The Astrophysical Journal, 2017 Abstract We study the behavior of eight diffuse interstellar bands (DIBs) in different interstellar environments, as characterized by the fraction of hydrogen in molecular form (f H2), with comparisons to the corresponding behavior of various known atomic and molecular species. The equivalent widths of the five “normal”
Haoyu Fan +12 more
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