Carbon monoxide in collapsing interstellar clouds

Formation, fractionation and excitation of carbon monoxide in diffuse clouds

Context. A wealth of observations of CO in absorption in diffuse clouds has accumulated in the past decade at uv and mm-wavelengths Aims. Our aims are threefold: a) To compare the uv and mm-wave results; b) to interpret 13CO and 12CO abundances in terms of the physical processes which separately and jointly determine them; c) to interpret observed J=1-0 rotational excitation and line brightness...

Molecular Line Profiles of Collapsing Gas Clouds

Emission line profiles of tracer molecule H2CO 140 GHz transition from gravitational core collapsing clouds in the dynamic process of forming protostars are calculated, using a simple ray-tracing radiative transfer model. Three self-similar dynamic insideout core collapse models – the conventional polytropic model, the empirical hybrid model and the isothermal model – for star-forming molecular...

Enigma of H3 + in Diffuse Interstellar Clouds

1. INTRODUCTION H 3 + is of fundamental importance to interstellar chemistry both because it is a hydrogenic species (and >90% of all nuclei in the universe are hydrogen nuclei; see Figure 1) and because it serves as the universal protonator, initiating a chain of ion-neutral reactions that is responsible for the formation of most interstellar molecules. The chemistry of H 3 + in dense (molecul...

Deuterium Fra tionation in Interstellar Clouds

Exotic clouds in the local interstellar medium

The neutral interstellar medium (ISM) inside the Local Bubble (LB) has been known to have properties typical of the warm neutral medium (WNM). However, several recent neutral hydrogen (HI) absorption experiments show evidence for the existence of at least several cold diffuse clouds inside or at the boundary of the LB, with properties highly unusual relative to the traditional cold neutral medi...