Oscillations of Starless Cores

If the split, asymmetric molecular spectral line profiles that are seen inmany starless cores are interpreted as indicative of global collapse orexpansion of the core then one possible implication is that most starless coreshave short lifetimes on the order of the collapse or sound crossing time scale.An alternative interpretation of the line profiles as indicative ofperturbations on an underlying equilibrium structure leads to the oppositeimplication, that many cores have long lifetimes. While evidence suggests thatsome cores are collapsing on a free-fall time scale, we show that observationsof some other starless cores can be reproduced by a model of non-radialoscillations about the equilibrium configuration of a pressure-bounded,thermally-supported sphere (Bonnor-Ebert sphere). We model the oscillations aslinear perturbations following a standard analysis developed for stellarpulsations and compare the column densities and molecular spectral lineprofiles predicted from a particular model to observations of the Bok globuleB68.Comment: submitted to the Astrophysical Journa