[en] Atomic and molecular clouds in the interstellar medium formed through the cooling of regions of hot gas. Here the collapse of a cooling protocloud is investigated: confinement is by an ambient medium rather than gravity. Large-scale thermal and magnetic pressure gradients across the cloud guide the collapse. The hot cloud is kept close to uniform by a short sound-crossing time. Prolate and oblate clouds with criteria for internal shock formation are analysed. Cool discs and filaments are formed from the spheroidal protoclouds. The type of collapse and final sheet column density depends sensitively on the cooling function. Further collapse, if constrained to take place along field lines, then produces cold filamentary structures and striated sheets. (author). 17 refs.; 2 figs

[en] Most detected planet-bearing binaries are in wide orbits, for which a high inclination, i_B , between the binary orbital plane and the plane of the planetary disk around the primary is likely to be common. In this paper, we investigate the intermediate stages-from planetesimals to planetary embryos/cores-of planet formation in such highly inclined cases. Our focus is on the effects of gas drag on the planetesimals' orbital evolution, in particular on the evolution of the planetesimals' semimajor axis distribution and their mutual relative velocities. We first demonstrate that a non-evolving axisymmetric disk model is a good approximation for studying the effects of gas drag on a planetesimal in the highly inclined case (30 deg. < i_B < 150 deg.). We then find that gas drag plays a crucial role, and the results can be generally divided into two categories, i.e., the Kozai-on regime and the Kozai-off regime, depending on the specific value of i_B . For both regimes, a robust outcome over a wide range of parameters is that planetesimals migrate/jump inward and pile up, leading to a severely truncated and dense planetesimal disk around the primary. In this compact and dense disk, collision rates are high but relative velocities are low, providing conditions that are favorable for planetesimal growth and potentially allow for the subsequent formation of planets.

[en] Formation of the large-scale structure is considered in the neutrino-dominated Universe. Thermal velocities survived since the epoch of Big-Bang are shown to limit significantly the maximum density of neutrinos in the firstly formed objects-''pancakes''. In the regions of caustics where in the case of cold medium the density used to achieve formally infinite value the real velocity dispersion exceeds it to the value about 10 or 20 higher than the mean density

No abstract available

[en] Topics covered include: hydrodynamics of interstellar matter; the equations of fluid flow; the assumptions underlying the equations of motion; sound waves, and the tendency to form sharp fronts; shocks and other fronts; ionization fronts; cocoons around early-type stars; magnetohydrodynamics of interstellar matter; plasmas, from the particle point of view; the plasma as a continuum; Alfven waves; Fermi acceleration; turbulence in fluids and in plasmas; hydromagnetic turbulence; high energy particles and hydromagnetic turbulence; and cosmic rays and interstellar matter. 7 figs

[en] Five fields, covering the COS-B error box of the source 2CG353+16, likely associated with the rho Oph dark cloud, have been observed by the Einstein Observatory. We give here some preliminary results on the central region of the cloud. The integrated luminosity of the five fields is Lsub(x) < or approximately equal to 10³³ erg.s^-1, yielding a ratio Lsub(x)/Lsub(γ) < or approximately equal to 1 for the γ-ray source

[en] Observations of interstellar molecules in regions of star formation are summarized. It is concluded that kinematics in molecular clouds are still poorly understood. The field is in need of some clever new ideas and/or observations. (Auth.)

[en] The amplitude scintillations of pulsars and the broadening of their profiles are different manifestations of the scattering of the signal by fine structure in the ionized interstellar gas. A newly developed pulsar-observing system at Culgoora is described and the first results on the pulse shapes of 11 highly scattered pulsars at 80 and 160 MHz are given. The information obtained is also used to test the hypothesis that the scattering properties of the interstellar medium are invariant within a distance of approximately 15 kpc of the sun

[en] The use of the world's largest optical telescope, the 6m telescope of Zelentchuk (U.S.S.R.) leads to some new features of the real structure of the interstellar gas (Hsub(α) emission) in the M33 galaxy. The number of the bubble like spherical 200 pc diameter HII regions and the 400 pc extension of the filamentary structures seem to be only limited by the sensitivity and space resolution. Bubble and filaments are likely evolved states of the interstellar gas dissipation process related to a rapide expansion due to the super-novae explosions and stellar winds

[en] Cold gas loss is thought to be important in star formation quenching and morphological transition during the evolution of S0 galaxies. In high-density environments, this gas loss can be achieved via many external mechanisms. However, in relatively isolated environments, where these external mechanisms cannot be efficient, the gas loss must then be dominated by some internal processes. We have performed Chandra analysis of hot gas in five nearby isolated S0 galaxies, based on the quantitative subtraction of various stellar contributions. We find that all the galaxies studied in the present work are X-ray faint, with the luminosity of the hot gas (L_X ) typically accounting for ∼< 5% of the expected Type Ia supernova (SN) energy injection rate. We have further compared our results with those from relevant recent papers, in order to investigate the energy budget, cold-hot gas relation, and gas removal from S0 galaxies in isolated environments. We find that elliptical and S0 galaxies are not significantly different in L_X at the low-mass end (typically with K-band luminosity L_K ∼< 10¹¹ L_sun,K). However, at the high-mass end, S0 galaxies tend to have significantly lower L_X than elliptical galaxies of the same stellar masses, as already shown in previous observational and theoretical works. We further discuss the potential relationship of the diffuse X-ray emission with the cold (atomic and molecular) gas content in the S0 and elliptical galaxies included in our study. We find that L_X /L²_K tends to correlate positively with the total cold gas mass (M_H2+Hi) for cold-gas-poor galaxies with M_H2+Hi∼<10⁸ M_sun, while they anti-correlate with each other for cold-gas-rich galaxies. This cold-hot gas relationship can be explained in a scenario of early-type galaxy evolution, with the leftover cold gas from the precursor star-forming galaxy mainly removed by the long-lasting Type Ia supernova (SN) feedback. The two different trends for cold-gas-rich and cold-gas-poor galaxies may be the results of the initial fast decreasing SN rate and the later fast decreasing mass loading to hot gas, respectively.