Resolving the physical conditions of concentrated cores in nearby clouds

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Stars form in molecular clouds out of smaller-scale "cores" of dense gas and dust. In principle, emission from gas and dust can be used to determine the physical conditions of such cores, especially in nearby clouds. Though some progress has been made towards this goal, current instruments have been limited in their ability to reveal the internal density, temperature and dynamical structures of cores. Such data are important because they provide the context from which we can understand how efficiently cores make stars, and provide insight into the formation of disks and outflows. In this proposal, we describe a comprehensive plan for two graduate students to explore the interior physical structures of cores, using new observational instrumentation that will become available soon. In particular, we focus on "concentrated cores," those of relatively high column density and small size that likely represent the epoch near the moment of gravitational core collapse, i.e., the formation of the protostar. Such cores will be found soon from current surveys of submillimetre continuum emission across several nearby molecular clouds. The students will undertake complementary projects, where each will recover aspects of the interior physical properties of concentrated cores using different tracers. In particular, one will observe NH3 line and radio continuum emission toward concentrated cores with the Green Bank Telescope (GBT) and the Expanded Very Large Array (EVLA), while the other will observe N2H+ and H2D+ line and submillimetre continuum emission toward the same cores with the James Clerk Maxwell Telescope (JCMT) and the Atacama Large Millimeter Array (ALMA).