Related papers: Water, O2 and Ice in Molecular Clouds
Interstellar ices are mainly composed of amorphous solid water (ASW) containing small amounts of hypervolatiles, such as O2, whose diffusion-limited reactions play a key role in space chemistry. Although O2 is an important precursor…
We present a study of gas-phase H2O and CO2 toward a sample of 14 massive protostars with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Modeling of the H2O spectra using a homogeneous model with a…
The desorption of molecular species from ice mantles back into the gas phase in molecular clouds results from a variety of very poorly understood processes. We have investigated three mechanisms; desorption resulting from H_2 formation on…
The HDO/H2O ratio in interstellar gas is often used to draw conclusions on the origin of water in star-forming regions and on Earth. In cold cores and in the outer regions of protoplanetary disks, gas-phase water comes from photodesorption…
We have investigated the time scale for formation of molecular clouds by examining the conversion of HI to H2 using a time-dependent model. H2 formation on dust grains and cosmic ray and photo destruction are included in one-dimensional…
H2 is the simplest and the most abundant molecule in the ISM, and its formation precedes the formation of other molecules. Understanding the dynamical influence of the environment and the interplay between the thermal processes related to…
The physical conditions in a collapsing cloud can be traced by observations of molecular lines. To correctly interpret these observations the abundance distributions of the observed species need to be derived. The chemistry in a collapsing…
The Herschel Space Observatory's recent detections of water vapor in the cold, dense cloud L1544 allow a direct comparison between observations and chemical models for oxygen species in conditions just before star formation. We explain a…
Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30m Large Program designed to estimate the S, C, N, and O depletions and gas ionization degree, X(e-), in a set of star-forming filaments of Taurus, Perseus and Orion. Our…
CO$_2$ is a major component of the icy mantles surrounding dust grains in planet and star formation regions. Understanding its photodesorption is crucial for explaining gas phase abundances in the coldest environments of the interstellar…
Molecular oxygen, O2 has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground…
We find that clouds of optically-thin, pressure-confined gas are prone to fragmentation as they cool below $\sim10^6$ K. This fragmentation follows the lengthscale $\sim{c}_{\text{s}}\,t_{\text{cool}}$, ultimately reaching very small scales…
We extend the analytic theory presented by Sternberg et al. (2014) and Bialy & Sternberg (2016) for the production of atomic hydrogen (HI) via FUV photodissociation at the boundaries of dense interstellar molecular (H$_2$) clouds, to also…
Solid O2 has been proposed as a possible reservoir for oxygen in dense clouds through freeze-out processes. The aim of this work is to characterize quantitatively the physical processes that are involved in the desorption kinetics of CO-O2…
Context. Millimetric observations have measured high degrees of molecular deuteration in several species seen around low-mass protostars. The Herschel Space Telescope, launched in 2009, is now providing new measures of the deuterium…
This work aims to study the unexplained sulfur depletion observed toward dense clouds and protostars. We made simulation experiments of the UV-photoprocessing and sublimation of H2S and H2S:H2O ice in dense clouds and circumstellar regions,…
The ultraviolet (UV) photodissociation of amorphous water ice at different ice temperatures is investigated using molecular dynamics (MD) simulations and analytical potentials. Previous MD calculations of UV photodissociation of amorphous…
Massive young stellar objects in the Magellanic Clouds show infrared absorption features corresponding to significant abundances of CO, CO$_2$ and H$_2$O ice along the line of sight, with the relative abundances of these ices differing…
Gaseous H2O has been detected in several cold astrophysical environments, where the observed abundances cannot be explained by thermal desorption of H2O ice or by H2O gas phase formation. These observations hence suggest an efficient…
Aims: Our aim is to determine the critical parameters in water chemistry and the contribution of water to the oxygen budget by observing and modelling water gas and ice for a sample of eleven low-mass protostars, for which both forms of…