Turbulent Fragmentation and Star Formation

We review the main results from recent numerical simulations of turbulent fragmentation and star formation. Specifically, we discuss the observed scaling relationships, the ``quiescent'' (subsonic) nature of many star-forming cores, their energy balance, their synthesized polarized dust emission, the ages of stars associated with the molecular gas from which they have formed, the mass spectra of clumps, and the density and column density probability distribution function of the gas. We then give a critical discussion on recent attempts to explain and/or predict the star formation efficiency and the stellar initial mass function from the statistical nature of turbulent fields. Finally, it appears that turbulent fragmentation alone cannot account for the final stages of fragmentation: although the turbulent velocity field is able to produce filaments, the spatial distribution of cores in such filaments is better explained in terms of gravitational fragmentation.Comment: 14 pages, 1 ps figure. Refered invited review, to appear in "Magnetic Fields and Star Formation: Theory versus Observations", eds. A.I. Gomez de Castro et al. (Kluwer), in pres

Humour in the post-war press: short stories of Gloria Fuertes in the falangist magazine Maravillas

The Spanish civil war entailed an impasse in the development of press as a communication platform. In fact, its instrumentalization for propaganda purposes explains its role in the consolidation of the new State. So, in the newspaper network created around the Movimiento Nacional (National Movement), the children’s press occupied a predominant place due to its contribution to the education of future generations. So much so, that the strategical-ideological aims imposed by the regime coexisted in these platforms together with the collaboration of artists of prominent aesthetical level. Such is the case of Gloria Fuertes (1917-1998), who gave life in the magazine Maravillas, to very popular characters such as Coleta and Pelines to disseminate their short stories once more, back in the eighties, in three monographic books: Coleta, la poeta (1982), Coleta, payasa ¿qué pasa? (1983) and Pelines (1986). However, such protagonists, beyond constituting aesthetical projections of the writer as heteronyms, would end up becoming authentic icons of children’s imagery

Six Myths on the Virial Theorem for Interstellar Clouds

It has been paid little or no attention to the implications that turbulent fragmentation has on the validity of at least six common assumptions on the Virial Theorem (VT), which are: (i) the only role of turbulent motions within a cloud is to provide support against collapse, (ii) the surface terms are negligible compared to the volumetric ones, (iii) the gravitational term is a binding source for the clouds, (iv) the sign of the second-time derivative of the moment of inertia determines whether the cloud is contracting or expanding, (v) interstellar clouds are in Virial Equilibrium (VE), and (vi) Larson's (1981) relations are the observational proof that clouds are in VE. Interstellar clouds cannot fulfill these assumptions, however, because turbulent fragmentation will induce flux of mass, moment and energy between the clouds and their environment, and will favor local collapse while may disrupt the clouds within a dynamical timescale. It is argued that, although the observational and numerical evidence suggests that interstellar clouds are not in VE, the so-called ``Virial Mass'' estimations, which actually should be called ``energy-equipartition mass'' estimations, are good order-of magnitude estimations of the actual mass of the clouds just because observational surveys will tend to detect interstellar clouds appearing to be close to energy equipartition. However, since clouds are actually out of VE, as suggested by asymmetrical line profiles, they should be transient entities. These results are compatible with observationally-based estimations for rapid star formation. , and call into question the models for the star formation efficiency based on clouds being in VE.Comment: Accepted by MNRAS. 9 pages, no figure