Related papers: When sticking influences H2 formation
The atomic-to-molecular hydrogen (H/H2) transition has been extensively studied as it controls the fraction of gas in a molecular state in an interstellar cloud. This fraction is linked to star-formation by the Schmidt-Kennicutt law. While…
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…
We study the evolution of molecular hydrogen on the grain surfaces and in the gas phase using both the rate equation (which tracks the average number of molecules) and the master equation (which tracks the expectation values of molecules).…
The majority of hydrogen in the interstellar medium (ISM) is in atomic form. The transition from atoms to molecules and, in particular, the formation of the H$_2$ molecule, is a key step in cosmic structure formation en route to stars.…
We study molecular hydrogen formation in and on solids. We construct a model with surface sites and bulk sites capable of describing (1) the motion and exchange of H and H_2 between surface and bulk, (2) the recombination of H and…
The energy to desorb atomic oxygen from an interstellar dust grain surface, $E_{\rm des}$, is an important controlling parameter in gas-grain models; its value impacts the temperature range over which oxygen resides on a dust grain.…
(Abridged). In this paper, we present results from a large set of numerical simulations that demonstrate that H2 formation occurs rapidly in turbulent gas. Starting with purely atomic hydrogen, large quantities of molecular hydrogen can be…
H2 formation remains a major issue for the understanding of interstellar physics. We investigate H2 formation in the interstellar medium at the light of the most recent experimental and theoretical data. We implemented detailed H2 formation…
Ultra-luminous infrared galaxies are among the most luminous objects in the local universe and are thought to be powered by intense star formation. It has been shown that in these objects the rotational spectral lines of molecular hydrogen…
In this work, we present an off-lattice Monte Carlo model of accretion and migration of hydrogen atoms on a rough surface of carbon dust grain. The migration of physisorbed atoms by means of thermal diffusion and quantum tunnelling through…
Physical conditions in dense and cold regions of interstellar clouds favour the formation of ice mantles on the surfaces of interstellar grains. It is predicted that most of the gaseous species heavier than H2 or He will adsorb onto the…
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…
It is commonly believed that it is unfavourable for adsorbed H atoms on carbonaceous surfaces to form H$_2$ without the help of incident H atoms. Using ring-polymer instanton theory to describe multidimensional tunnelling effects, combined…
At the low temperatures of interstellar dust grains, it is well established that surface chemistry proceeds via diffusive mechanisms of H atoms weakly bound (physisorbed) to the surface. Until recently, however, it was unknown whether atoms…
We investigate the formation and evolution of interstellar dust-grain ices under dark-cloud conditions, with a particular emphasis on CO2. We use a three-phase model (gas/surface/mantle) to simulate the coupled gas--grain chemistry,…
We present a detailed description of a phenomenological H2 formation model and local star formation prescription based on the density of molecular (rather than total) gas. Such approach allows us to avoid the arbitrary density and…
Grain-surface reactions play an essential role in interstellar chemistry, since dust grain catalyses reactions at its surface allowing for the formation of molecules. We used a chemical model in which both gas-phase and grain-surface…
We describe a phenomenological model for molecular hydrogen formation suited for applications in galaxy formation simulations, which includes on-equilibrium formation of molecular hydrogen on dust and approximate treatment of both its…
The temperature of newly forming dust is controlled by the radiation field. As dust forms around stars, stellar transients, quasars or supernovae, the grains must grow through a regime where they are stochastically heated by individual…
We combine recent ISO observations of the vibrational ground state lines of H2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground-based telescopes in order to constrain the formation…