Related papers: Diffuse Molecular Cloud Densities from UV Measurem…
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…
Observations of dense molecular gas lie at the basis of our understanding of the density and temperature structure of protostellar envelopes and molecular outflows. We aim to characterize the properties of the protostellar envelope,…
Based on measurements with the Effelsberg 100-m telescope, a multi-line study of molecular species is presented toward the gravitational lens system PKS1830-211. Obtaining average radial velocities and performing Large Velocity Gradient…
The VUV absorption cross sections of most molecular solids present in interstellar ice mantles with the exception of H2O, NH3, and CO2 have not been reported yet. Models of ice photoprocessing depend on the VUV absorption cross section of…
Using arguments parallel to those used in support of using H2CO as a sensitive probe of temperature and density in molecular clouds, we measured the J=7-6 and J=10-9 transitions of thioformaldehyde (H2CS) in several hot core sources. The…
We modelled \HH\ and CO formation incorporating the fractionation and selective photodissociation affecting CO when \AV\ $\la2$mag. UV absorption measurements typically have N(\cotw)/N(\coth) $\approx 65$ that are reproduced with the…
We discuss the interstellar absorption from many atomic and molecular species seen in high-resolution $HST$/STIS UV and high-S/N optical spectra of the moderately reddened B3-5~V star HD~62542. This remarkable sight line exhibits both very…
In recent decades, significant attention has been dedicated to analytical and observational studies of the atomic hydrogen (HI) to molecular hydrogen (H2) transition in the interstellar medium. We focussed on the Draco diffuse cloud to gain…
Molecular hydrogen (H$_2$) is by far the most abundant molecule in the Universe. However, due to the low emissivity of H$_2$, carbon monoxide (CO) is widely used instead to trace molecular gas in galaxies. The relative abundances of these…
Diffusion of atoms and molecules is a key process for the chemical evolution in the star forming regions of the interstellar medium. Accurate data on the mobility of many important interstellar species is however often not available and…
We have computed line emission cooling rates for the main cooling species in models of interstellar molecular clouds. The models are based on numerical simulations of super-sonic magneto-hydrodynamic (MHD) turbulence. Non-LTE radiative…
Motivated by recent observations with Herschel/PACS, and the availability of new rate coefficients for the collisional excitation of CO (Yang et al. 2010), the excitation of warm astrophysical CO is revisited with the use of numerical and…
Utilising previous work by the authors on the spin-coupled rotational cross-sections for electron-CN collisions, data for the associated rate coefficients is presented. Data on rotational, fine-structure and hyperfine-structure transition…
Neither HI nor CO emission can reveal a significant quantity of so-called dark gas in the interstellar medium (ISM). It is considered that CO-dark molecular gas (DMG), the molecular gas with no or weak CO emission, dominates dark gas. We…
Observations of CO+ suggest column densities on the order 10^12 cm^-2 that can not be reproduced by many chemical models. CO+ is more likely to be destroyed than excited in collisions with hydrogen. An anomalous excitation mechanism may…
Using the PMO-13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ emission toward the sky region centered at $l$=$209.7^\circ$,…
CO$_2$ is an important, stable, and abundant molecule in the Universe, but it is very difficult to detect because it has no observable pure rotational transitions. The unique sensitivity and resolution of the James Webb Space Telescope…
The origin of rovibrational H_2 emission in the central galaxies of cooling flow clusters is poorly understood. Here we address this issue using data from our near-infrared spectroscopic survey of 32 of the most line luminous such systems,…
Carbon monoxide (CO) is the most commonly used tracer of molecular gas in the inner regions of protoplanetary disks. CO can be used to constrain the excitation and structure of the circumstellar environment. Absorption line spectroscopy…
The most usual tracer of molecular gas is line emission from CO. However, the reliability of that tracer has long been questioned in environments different from the Milky Way. We study the relationship between H2 and CO abundances using a…