The evolution of low-mass dense cores

Although the standard model of star formation has served us well for over 20 years, its details are still a matter of debate. In particular, questions related to the effect of environment on star formation efficiency and the relative and absolute lifetimes of the different evolutionary phases are best answered by observations of large samples of cores. Such observations are only now becoming available, thanks to an impressive suite of new instruments that allow mapping studies in a reasonable time. Essential information such as whether cores are gravitationally bound or unbound, whether they are dominated by thermal or turbulent motions, and whether they are contracting or collapsing, or expanding, can only be obtained through molecular line observations. Isolated cores are the best places in which to study the star formation process, due to their simple nature and freedom from the confusing effects of crowded regions. We propose to map in N2H+, CS, and C18O, 40 cores that we have observed in the MIR and mm continuum. When combined with our existing data on 90 cores that probe different evolutionary stages, these data will provide the most complete, unbiased view of core evolution and the initial conditions for star formation.