The interstellar medium is observed in a hierarchical fractal structure over several orders of magnitude in scale. Aiming to understand the origin of this structure, we carry out numerical simulations of molecular cloud fragmentation, taking into account self-gravity, dissipation and energy input. Selfgravity is computed through a tree code, with fully or quasi periodic boundary conditions. Ene...

The nearby dwarf elliptical galaxy NGC 205 offers a unique opportunity for high resolution studies of the interstellar medium in an elliptical galaxy. The present paper investigates the distribution of molecular gas, molecular line ratios, and the relationships between atomic gas, molecular gas, and dust in this galaxy. The line ratios 12 CO(2-1)/(1-0) and 12 CO(1-0)/ 13 CO(1-0) in one of the m...

A model, based on different observations of the local interstellar medium, indicates the presence of a very close interstellar cloud in front of the Scorpius-Ophiuchus association (almost in the direction of the galactic center) approaching the solar system from a distance of about 0.03 pc at a velocity of about 15-20 km s. These observations are as follows: 1. The strong gradient of the hydrog...

The orientation of the local interstellar magnetic field introduces asymmetries in the heliosphere that affect the location of heliospheric radio emissions and the streaming direction of ions from the termination shock of the solar wind. We combined observations of radio emissions and energetic particle streaming with extensive three-dimensional magnetohydrodynamic computer simulations of magne...

Interstellar material around the Sun is typical for our neighborhood of the Galaxy. The physical properties and kinematics of the partially ionized interstellar material (ISM) near the Sun are typical of warm diffuse clouds in the solar vicinity. The direction of the interstellar magnetic field at the heliosphere, the polarization of light from nearby stars, and the kinematics of nearby clouds ...

Pickup ions, created by ionization of slow moving atoms and molecules well inside the heliosphere, provide us with a new tool to probe remote regions in and beyond the heliosphere and to study injection and acceleration processes in the solar wind. Comprehensive and continuous measurements of H, He, C, N, O, Ne and other pickup ions, especially with the Solar Wind Ion Composition Spectrometer (...

We use the absorption features from the resonance transitions of neutral argon at 1048 and 1066 A to determine interstellar argon abundances or their lower limits toward nine early-type stars. These features were observed with the Interstellar Medium Absorption Proole Spectrograph (IMAPS) along sight lines with low reddening and low fractional abundances of molecular hydrogen. Four of the sight...

Almost all interstellar objects contain inherent inhomogeneity. The inhomogeneity can manifest in many different ways, such as the uneven matter distribution in a molecular cloud, or the tangled magnetic field distribution in a Bok globule. The dynamics of interstellar objects is thus often governed by the interaction between astrophysical flows or shocks such as supernova blast waves with inho...

We present spectrophotometric imaging mid–IR observations of the reflection nebula Ced 201. Ced 201 is a part of a molecular cloud illuminated by a B9.5V star moving through it at more than 12 km s−1. The spectra of Ced 201 give evidence for transformation of very small carbonaceous grains into the carriers of the Aromatic Infrared Bands (AIBs), due to the radiation field of the illuminating st...