Related papers: Testing Molecular-Cloud Fragmentation Theories: Se…
Star formation is intimately linked to the dynamical evolution of molecular clouds. Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass via accretion from the surrounding cloud…
We discuss the fragmentation of a filamentary cloud on the basis of a 1-dimensional hydrodynamical simulation of a self-gravitating gas cloud. The simulation shows that dense cores are produced with a semi-regular interval in space and time…
We explore whether observed molecular clouds could include a substantial population of unbound clouds. Using simulations which include only turbulence and gravity, we are able to match observed relations and naturally reproduce the observed…
Observations of magnetic field strengths imply that molecular cloud fragments are individually close to being in a magnetically critical state, even though both magnetic field and column density measurements range over two orders of…
We review recent advances in the analytical and numerical modeling of the star formation rate in molecular clouds and discuss the available observational constraints. We focus on molecular clouds as the fundamental star formation sites,…
We examine the linear stability of an isothermal filamentary cloud permeated by a perpendicular magnetic field. Our model cloud is assumed to be supported by gas pressure against the self-gravity in the unperturbed state. For simplicity,…
This paper re-examines the problem of ambipolar diffusion as a mechanism for the production and runaway evolution of centrally condensed molecular cloud cores, a process that has been termed the gravomagneto catastrophe. Our calculation…
The thermal and chemical evolution of star-forming clouds is studied for different gas metallicities, Z, using the model of Omukai (2000), updated to include deuterium chemistry and the effects of cosmic microwave background (CMB)…
We follow the ambipolar-diffusion--driven formation and evolution of a fragment in a magnetically supported molecular cloud, until a hydrostatic protostellar core forms at its center. This problem was formulated in Paper I. We determine the…
We re-examine critically the estimates of the duration of different phases of star formation and the lifetimes of molecular clouds, based on the ages of T-Tauri stars, age spreads of stars in clusters, and statistics of pre-stellar cores.…
We present a series of simulations of the fragmentation of a molecular cloud, leading to the formation of a cluster of protostellar cores. The purpose of these simulations is to address a specific numerical problem called artificial…
Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass from the surrounding cloud material. This process is investigated, using numerical models of self-gravitating molecular cloud…
This review summarizes the argument for molecular clouds being dominated by turbulence, most likely super-Alfvenic turbulence. Five lines of observational evidence are given: molecular linewidths and line shapes, nonequilibrium chemical…
Magnetic fields (B-fields) play an important role in molecular cloud fragmentation and star formation, but are very difficult to detect. The temporal correlation between the field strength (B) and gas density (n) of an isolated cloud has…
We present an idealized, spherical model of the evolution of a magnetized molecular cloud due to ambipolar diffusion. This model allows us to follow the quasi-static evolution of the cloud's core prior to collapse and the subsequent…
Molecular clouds are the most important incubators of young stars clustered in various stellar structures whose spatial extension can vary from a few AU to several thousand AU. Although the reality of these stellar systems has been…
We present results from an extensive set of simulations of gravitational fragmentation in the presence of magnetic fields and ambipolar diffusion. The average fragmentation spacing in the nonlinear phase of evolution is in excellent…
I present an overview of the hierarchy of structures existing in the interstellar medium (ISM) and the possible mechanisms that cause the fragmentation of one level into the next, with the formation of stars as its last step. Within this…
Subsequent to Paper I, the evolution and fragmentation of a rotating magnetized cloud are studied with use of three-dimensional MHD nested-grid simulations. After the isothermal runaway collapse, an adiabatic gas forms a protostellar first…
A series of recent theoretical atomic diffusion studies has address the challenging problem of predicting inhomogeneous vertical and horizontal chemical element distributions in the atmospheres of magnetic ApBp stars. Here we critically…