| Description |
Prestellar cores are crucial to our understanding of star formation. It is at this evolutionary stage that the stellar mass is set. If we are to understand the origin of the stellar IMF, we must therefore study the masses of the prestellar cores from which the stars are formed. There is currently a large uncertainty in the measured prestellar core mass that we obtain from far-IR and submillimetre observations. This uncertainty is caused by our inability to simultaneously determine the column density, temperature and dust emissivity index from photometric observations. Physical processes such as grain growth, or ice-mantle formation, which are affected by changes in density and temperature, will change the dust emissivity index. By simply taking a canonical value for the emissivity index, we cannot determine the correct mass for prestellar cores.
The SPIRE FTS allows us to break this degeneracy for the first time, and simultaneously measure the column density, temperature and dust emissivity index, and therefore determine accurate masses. We propose to map 16 prestellar cores with the SPIRE FTS, and hence generate accurate maps of their column density. We will map each core using the full FTS field of view. We will be able to determine the absolute value of the dust emissivity index, and also see whether it varies across each of the cores. We have selected cores in different environments in order to study the core-to-core, and cloud-to-cloud variations in the dust properties. We will be able use this information about the relation between the three measured parameters, to more accurately determine masses for a much larger sample of cores for which only photometric data are available |
