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{It is well established that the atomic interstellar hydrogen is filling the galaxies and constitutes the building blocks of molecular clouds.} {To understand the formation and the evolution of molecular clouds, it is necessary to…

Astrophysics of Galaxies · Physics 2015-05-14 E. Audit , P. Hennebelle

Molecular hydrogen in silicon has been studied by path-integral molecular dynamics simulations in the canonical ensemble. Finite-temperature properties of these point defects were analyzed in the range from 300 to 900 K. Interatomic…

Materials Science · Physics 2009-07-31 Carlos P. Herrero , Rafael Ramirez

A possible formation mechanism of hydrogen molecules on a galactic scale is examined. We are interested especially in the role of hydrogen molecules for formation and evolution of primordial galaxies. Then, formation process of hydrogen…

Astrophysics · Physics 2015-06-24 Hideyuki Kamaya , Hiroyuki Hirashita

Many theoretical and laboratory studies predict H2 to be formed in highly excited ro-vibrational states. The consequent relaxation of excited levels via a cascade of infrared transitions might be observable in emission from suitable…

Astrophysics of Galaxies · Physics 2015-05-20 Farahjabeen Islam , Cesare Cecchi-Pestellini , Serena Viti , Silvia Casu

The accumulation, compression and cooling of the ambient interstellar medium (ISM) in large-scale flows powered by OB cluster feedback can drive the production of dense molecular clouds. We review the current state of the field, with a…

Astrophysics of Galaxies · Physics 2013-04-10 J. R. Dawson

There has always been a great deal of interest in the formation of H2 as well as in the binding energy released upon its formation on the surface of dust grains. The present work aims at collecting experimental evidence for how the bond…

Methanol and its precursor formaldehyde are among the most studied organic molecules in the interstellar medium and are abundant in the gaseous and solid phases. We recently developed a model to simulate CO hydrogenation via H atoms on…

Astrophysics of Galaxies · Physics 2015-05-14 H. M. Cuppen , E. F. van Dishoeck , E. Herbst , A. G. G. M. Tielens

The effect of line overlap in the Lyman and Werner bands, often ignored in galactic studies of the atomic-to-molecular transition, greatly enhances molecular hydrogen self-shielding in low metallicity environments, and dominates over dust…

Astrophysics of Galaxies · Physics 2016-08-01 Nickolay Y. Gnedin , Bruce T. Draine

Glycoaldehyde, ethylene glycol, and methyl formate are complex organic molecules that have been observed in dark molecular clouds. Because there is no efficient gas-phase route to produce these species, it is expected that a low-temperature…

Solar and Stellar Astrophysics · Physics 2020-02-12 M. A. J. Simons , T. Lamberts , H. M. Cuppen

I review the capabilities of H$\alpha$ observations to constrain some aspects of the current models of the interstellar medium. In particular, it is shown that turbulence is a necessary ingredient of any viable model, since most of the…

Astrophysics · Physics 2015-06-24 Andrea Ferrara

Silicon is present in interstellar dust grains, meteorites and asteroids, and to date thirteen silicon-bearing molecules have been detected in the gas-phase towards late-type stars or molecular clouds, including silane and silane…

Even though water is the main constituent in interstellar icy mantles, its chemical origin is not well understood. Three different formation routes have been proposed following hydrogenation of O, O2, or O3, but experimental evidence is…

Astrophysics · Physics 2009-11-13 S. Ioppolo , H. M. Cuppen , C. Romanzin , E. F. van Dishoeck , H. Linnartz

We use one-dimensional radiative transfer simulations to study the evolution of H_2 gas-phase (H^- catalyzed) formation and photo-dissociation regions in the primordial universe. We find a new positive feedback mechanism capable of…

Astrophysics · Physics 2009-10-31 Massimo Ricotti , Nickolay Y. Gnedin , J. Michael Shull

Context: Molecular hydrogen ($\rm{H_2}$) is crucial in galaxy formation and evolution, serving as the main fuel for star formation (SF). In metal-enriched environments, $\rm{H_2}$ primarily forms on interstellar dust grain surfaces.…

Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. Especially, saturated, hydrogen-rich molecules are formed through surface chemistry.…

Astrophysics of Galaxies · Physics 2022-02-11 H. M. Cuppen , A. Fredon , T. Lamberts , E. M. Penteado , M. Simons , C. Walsh

Formation of interstellar clouds as a consequence of thermal instability is studied using two-dimensional two-fluid magnetohydrodynamic simulations. We consider the situation of converging, supersonic flows of warm neutral medium in the…

Astrophysics of Galaxies · Physics 2015-05-14 Tsuyoshi Inoue , Shu-ichiro Inutsuka

Atomic hydrogen (HI) is a critical stepping stone in the gas evolution cycle of the interstellar medium (ISM) of the Milky Way. Hi traces both the cold, premolecular state before star formation and the warm, diffuse ISM before and after…

Astrophysics of Galaxies · Physics 2023-07-18 Naomi M. McClure-Griffiths , Snezana Stanimirovic , Daniel R. Rybarczyk

Continuous-time, random-walk Monte Carlo simulations of H2 formation on grains have been performed for surfaces that are stochastically heated by photons. We have assumed diffuse cloud conditions and used a variety of grains of varying…

Astrophysics · Physics 2009-11-11 H. M. Cuppen , O. Morata , Eric Herbst

Aims. Interstellar dust grains, because of their catalytic properties, are crucial to the formation of H2, the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick…

Solar and Stellar Astrophysics · Physics 2015-05-28 S. Cazaux , S. Morisset , M. Spaans , A. Allouche

We study the formation of H2 in the ISM, using a modified version of the astrophysical magnetohydrodynamical code ZEUS-MP that includes a non-equilibrium treatment of the formation and destruction of H2. We examine two different…

Astrophysics · Physics 2008-11-26 S. C. O. Glover , M. -M. Mac Low