Molecule Formation in Cool, Dense Interstellar Clouds

Chlorine in Dense Interstellar Clouds: the Abundance

We report the first detection of a chlorine-bearing molecular species in the interstellar medium via emission from the J = 1----> 0 transition of HCl at 625.9 GHz toward OMC-1. The relative strengths, widths, and velocities of the resolved hyperfine components are consistent with moderate optical depth emission originating from dense, quiescent molecular cloud material (VLsR = 9 km s1). The ove...

Elemental nitrogen partitioning in dense interstellar clouds.

Many chemical models of dense interstellar clouds predict that the majority of gas-phase elemental nitrogen should be present as N(2), with an abundance approximately five orders of magnitude less than that of hydrogen. As a homonuclear diatomic molecule, N(2) is difficult to detect spectroscopically through infrared or millimeter-wavelength transitions. Therefore, its abundance is often inferr...

On water ice formation in interstellar clouds

A model is proposed for the formation of water ice mantles on grains in interstellar clouds. This occurs by direct accretion of monomers from the gas, be they formed by gas or surface reactions. The formation of the first monolayer requires a minimum extinction of interstellar radiation, sufficient to lower the grain temperature to the point where thermal evaporation of monomers is just offset ...

The Chemistry of Transient Dense Cores in Interstellar Clouds

Formation of Interstellar Clouds: Parker Instability with Phase Transitions

We follow numerically the nonlinear evolution of the Parker instability in the presence of phase transitions from a warm to a cold HI interstellar medium in two spatial dimensions. The nonlinear evolution of the system favors modes that allow the magnetic field lines to cross the galactic plane. Cold HI clouds form with typical masses ≃ 10 M⊙, mean densities ≃ 20 cm, mean magnetic field strengt...