We present high-resolution spectra (R ∼ 49,000) of stars that have parallax measurements from the Hipparcos satellite and are projected along the line of sight to the two nearest known star forming clouds to the Sun: MBM12 and MBM20. The spectra were obtained with the FOCES Echelle Spectrograph at the 2.2 meter telescope in Calar Alto, Spain and the wavelength range was chosen to include the in...

We compare the statistical properties of J=1→0 CO spectra observed in the Perseus Molecular Cloud with synthetic J=1→0 CO spectra from a 5 pc model cloud. The synthetic spectra are computed solving the non–LTE radiative transfer problem for a model cloud obtained as solutions of the 3–D magneto–hydrodynamic (MHD) equations in both the highly supersonic and super–Alfvénic regimes of random flows...

Early studies of molecular gas in M33 used the CO J=1-0 transition to map out the total gas content in the inner kiloparsec of the galaxy and to study the properties of the giant molecular cloud population. In this review, I discuss recent detailed studies of individual molecular clouds in M33 in higher rotational transitions of CO, CO, and the fine structure line of atomic carbon. These data r...

There exists observational evidence that the interstellar medium has a fractal structure in a wide range of spatial scales. The measurement of the fractal dimension (Df) of interstellar clouds is a simple way to characterize this fractal structure, but several factors, both intrinsic to the clouds and to the observations, may contribute to affect the values obtained. In this work we study the e...

We propose a novel mathematical method to construct an exact polytropic sphere in self-gravitating hydrostatic equilibrium, improving the non-linear Poisson equation. The central boundary condition for the present equation requires a ratio of gas pressure to total one at the centre, which is uniquely identified by the whole mass and molecular weight of the system. The special solution derived f...

Context. Over the last decade, several groups of young (mainly low-mass) stars have been discovered in the solar neighbourhood (closer than ∼100 pc), thanks to cross-correlation between X-ray, optical spectroscopy and kinematic data. These young local associations – including an important fraction whose members are Hipparcos stars – offer insights into the star formation process in low-density ...

In this paper we show results of numerical simulations for the turbulence in the interstellar medium. These results were obtained using a Riemann solver-free numerical scheme for high-Mach number hyperbolic equations. Here we especially concentrate on the physical properties of the ISM. That is, we do not present turbulence simulations trimmed to be applicable to the interstellar medium. The si...

Several nearby individual low column density interstellar cloudlets have been identified based on kinematical features evident in high-resolution Ca observations near the Sun. One of these cloudlets, the ‘Apex Cloud” (AC), is within 5 pc of the Sun in the solar apex direction. The question of which interstellar cloud will constitute the next galactic environment of the Sun in principle can be d...

Over the last decade, several groups of young (mainly low-mass) stars have been discovered in the solar neighbourhood (closer than∼ 100 pc), thanks to cross-correlation between X-ray, optical spectroscopy and kinematic data. These young local associations including an important fraction whose members are Hipparcos stars offer insights into the star formation process in low-density environments,...